docs: updated gotchas section

Fix emplace Signature

doc/00_optional.qbk

@@ -2,7 +2,7 @@
     [quickbook 1.4]
     [authors [Cacciola Carballal, Fernando Luis]]
     [copyright 2003-2007 Fernando Luis Cacciola Carballal]
-    [copyright 2014-2015 Andrzej Krzemieński]
+    [copyright 2014-2016 Andrzej Krzemieński]
     [category miscellaneous]
     [id optional]
     [dirname optional]
@@ -83,7 +83,7 @@ This is how you solve it with `boost::optional`:
 [include 14_io.qbk]
 [include 15_optional_references.qbk]
 [include 16_in_place_factories.qbk]
-[include 17_optional_bool.qbk]
+[include 17_gotchas.qbk]
 [include 18_exception_safety.qbk]
 [include 19_type_requirements.qbk]
 [include 1A_on_performance.qbk]

doc/11_development.qbk

@@ -228,7 +228,7 @@ For value access operations `optional<>` uses operators `*` and `->` to
 lexically warn about the possibly uninitialized state appealing to the
 familiar pointer semantics w.r.t. to null pointers.
 
-[warning
+[caution
 However, it is particularly important to note that `optional<>` objects
 are not pointers. [_`optional<>` is not, and does not model, a pointer].
 ]

doc/15_optional_references.qbk

@@ -1,6 +1,8 @@
 
 [section Optional references]
 
+[section Overview]
+
 This library allows the template parameter `T` to be of reference type:
 `T&`, and to some extent, `T const&`.
 
@@ -21,7 +23,7 @@ will nonetheless refer to the same object.
 * Value-access will actually provide access to the referenced object
 rather than the reference itself.
 
-[warning On compilers that do not conform to Standard C++ rules of reference binding, operations on optional references might give adverse results: rather than binding a reference to a designated object they may create an unexpected temporary and bind to it. For more details see [link boost_optional.dependencies_and_portability.optional_reference_binding Dependencies and Portability section].]
+[caution On compilers that do not conform to Standard C++ rules of reference binding, some operations on optional references are disabled in order to prevent subtle bugs. For more details see [link boost_optional.dependencies_and_portability.optional_reference_binding Dependencies and Portability section].]
 
 [heading Rvalue references]
 
@@ -118,3 +120,4 @@ In such a scenario, you can assign the value itself directly, as in:
     *opt=value;
 
 [endsect]
+[endsect]

doc/17_gotchas.qbk

@@ -0,0 +1,111 @@
+[section Gotchas]
+
+[section A note about optional<bool>]
+
+`optional<bool>` should be used with special caution and consideration.
+
+First, it is functionally similar to a tristate boolean (false, maybe, true)
+—such as __BOOST_TRIBOOL__— except that in a tristate boolean, the maybe state
+[_represents a valid value], unlike the corresponding state of an uninitialized
+`optional<bool>`.
+It should be carefully considered if an `optional<bool>` instead of a `tribool`
+is really needed.
+
+Second, although `optional<>` provides a contextual conversion to `bool` in C++11,
+ this falls back to an implicit conversion on older compilers. This conversion refers
+ to the initialization state and not to the contained value. Using `optional<bool>`
+ can lead to subtle errors due to the implicit `bool` conversion:
+
+    void foo ( bool v ) ;
+    void bar()
+    {
+        optional<bool> v = try();
+
+        // The following intended to pass the value of 'v' to foo():
+        foo(v);
+        // But instead, the initialization state is passed
+        // due to a typo: it should have been foo(*v).
+    }
+
+The only implicit conversion is to `bool`, and it is safe in the sense that
+typical integral promotions don't apply (i.e. if `foo()` takes an `int`
+instead, it won't compile).
+
+Third, mixed comparisons with `bool` work differently than similar mixed comparisons between pointers and `bool`, so the results might surprise you:
+
+    optional<bool> oEmpty(none), oTrue(true), oFalse(false);
+    
+    if (oEmpty == none);  // renders true
+    if (oEmpty == false); // renders false!
+    if (oEmpty == true);  // renders false!
+     
+    if (oFalse == none);  // renders false
+    if (oFalse == false); // renders true!
+    if (oFalse == true);  // renders false
+    
+    if (oTrue == none);   // renders false
+    if (oTrue == false);  // renders false
+    if (oTrue == true);   // renders true
+
+In other words, for `optional<>`, the following assertion does not hold:
+
+    assert((opt == false) == (!opt));
+[endsect]
+
+[section Moved-from `optional`]
+
+When an optional object that contains a value is moved from (is a source of move constructor or assignment) it still contains a value and its contained value is left in a moved-from state. This can be illustrated with the following example.
+
+    optional<std::unique_ptr<int>> opi {std::make_unique<int>(1)};
+    optional<std::unique_ptr<int>> opj = std::move(opi);
+    assert (opi);
+    assert (*opi == nullptr);
+
+Quite a lot of people expect that when an object that contains a value is moved from, its contained value should be destroyed. This is not so, for performance reasons. Current semantics allow the implementation of `boost::opiotnal<T>` to be trivially copyable when `T` is trivial.
+[endsect]
+
+[section Mixed relational comparisons]
+
+Because `T` is convertible to `optional<T>` and because `opiotnal<T>` is __SGI_LESS_THAN_COMPARABLE__ when `T` is __SGI_LESS_THAN_COMPARABLE__,
+you can sometimes get an unexpected runtime result where you would rather expect a compiler error:
+
+    optional<double> Flight_plan::weight(); // sometimes no weight can be returned
+
+    bool is_aircraft_too_heavy(Flight_plan const& p)
+    {
+       return p.weight() > p.aircraft().max_weight(); // compiles!
+    }                                                 // returns false when the optional contains no value 
+
+[endsect]
+
+[section False positive with -Wmaybe-uninitialized]
+
+Sometimes on GCC compilers below version 5.1 you may get an -Wmaybe-uninitialized warning when copiling with option -02 on a perfectly valid `boost::optional` usage. For instance in this program:
+
+    #include <boost/optional.hpp>
+
+    boost::optional<int> getitem();
+
+    int main(int argc, const char *[])
+    {
+      boost::optional<int> a = getitem();
+      boost::optional<int> b;
+
+      if (argc > 0)
+        b = argc;
+
+      if (a != b)
+        return 1;
+
+      return 0;
+    }
+    
+This is a bug in the compiler. As a workaround (provided in [@http://stackoverflow.com/questions/21755206/how-to-get-around-gcc-void-b-4-may-be-used-uninitialized-in-this-funct this Stack Overflow question]) use the following way of initializing an optional containing no value:
+
+    boost::optional<int> b = std::make_optional(false, int());
+
+This is obviously redundant, but makes the warning disappear.
+
+[endsect]
+
+[endsect]

doc/17_optional_bool.qbk

@@ -1,52 +0,0 @@
-
-[section A note about optional<bool>]
-
-`optional<bool>` should be used with special caution and consideration.
-
-First, it is functionally similar to a tristate boolean (false, maybe, true)
-—such as __BOOST_TRIBOOL__— except that in a tristate boolean, the maybe state
-[_represents a valid value], unlike the corresponding state of an uninitialized
-`optional<bool>`.
-It should be carefully considered if an `optional<bool>` instead of a `tribool`
-is really needed.
-
-Second, although `optional<>` provides a contextual conversion to `bool` in C++11,
- this falls back to an implicit conversion on older compilers. This conversion refers
- to the initialization state and not to the contained value. Using `optional<bool>`
- can lead to subtle errors due to the implicit `bool` conversion:
-
-    void foo ( bool v ) ;
-    void bar()
-    {
-        optional<bool> v = try();
-
-        // The following intended to pass the value of 'v' to foo():
-        foo(v);
-        // But instead, the initialization state is passed
-        // due to a typo: it should have been foo(*v).
-    }
-
-The only implicit conversion is to `bool`, and it is safe in the sense that
-typical integral promotions don't apply (i.e. if `foo()` takes an `int`
-instead, it won't compile).
-
-Third, mixed comparisons with `bool` work differently than similar mixed comparisons between pointers and `bool`, so the results might surprise you:
-
-    optional<bool> oEmpty(none), oTrue(true), oFalse(false);
-    
-    if (oEmpty == none);  // renders true
-    if (oEmpty == false); // renders false!
-    if (oEmpty == true);  // renders false!
-     
-    if (oFalse == none);  // renders false
-    if (oFalse == false); // renders true!
-    if (oFalse == true);  // renders false
-    
-    if (oTrue == none);   // renders false
-    if (oTrue == false);  // renders false
-    if (oTrue == true);   // renders true
-
-In other words, for `optional<>`, the following assertion does not hold:
-
-    assert((opt == false) == (!opt));
-[endsect]

doc/1A_on_performance.qbk

@@ -23,7 +23,7 @@ Given type `optional<int>`, and assuming that `sizeof(int) == 4`, we will get `s
 
 [$images/opt_align1.png]
 
-This means you can fit twice as many `int`s as `optional<int>`s into the same space of memory. Therefore, if the size of the objects is critical for your application (e.g., because you want to utilize your CPU cache in order to gain performance) and you have determined you are willing to trade the code clarity, it is recommended that you simply go with type `int` and use some 'magic value' to represent ['not-an-int].
+This means you can fit twice as many `int`s as `optional<int>`s into the same space of memory. Therefore, if the size of the objects is critical for your application (e.g., because you want to utilize your CPU cache in order to gain performance) and you have determined you are willing to trade the code clarity, it is recommended that you simply go with type `int` and use some 'magic value' to represent ['not-an-int], or use something like [@https://github.com/akrzemi1/markable `markable`] library.
 
 Even if you cannot spare any value of `int` to represent ['not-an-int] (e.g., because every value is useful, or you do want to signal ['not-an-int] explicitly), at least for `Trivial` types you should consider storing the value and the `bool` flag representing the ['null-state] separately. Consider the following class:
 

doc/27_ref_optional_synopsis.qbk

@@ -9,21 +9,80 @@
 ]
 
 
-[#ref_header_optional_optional_hpp][section:header_optional_optional Synopsis]
+[#ref_header_optional_optional_hpp] [section:header_optional_optional Synopsis]
 
     ```// In Header: <`[@boost:/boost/optional/optional.hpp boost/optional/optional.hpp]'''<phrase role="comment">&gt;</phrase>'''``
 
     namespace boost {
 
+    template <class T>
+    class optional ; ``[link reference_operator_template __GO_TO__]``
+    
+    template <class T>
+    class optional<T&> ; ``[link reference_operator_template_spec __GO_TO__]``
+    
+    template<class T> inline bool operator == ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_equal_optional_optional __GO_TO__]``
+
+    template<class T> inline bool operator != ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_not_equal_optional_optional __GO_TO__]``
+
+    template<class T> inline bool operator <  ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_less_optional_optional __GO_TO__]``
+
+    template<class T> inline bool operator >  ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_greater_optional_optional __GO_TO__]``
+
+    template<class T> inline bool operator <= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_less_or_equal_optional_optional __GO_TO__]``
+
+    template<class T> inline bool operator >= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_greater_or_equal_optional_optional __GO_TO__]``
+    
+    template<class T> inline bool operator == ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_equal_optional_none __GO_TO__]``
+
+    template<class T> inline bool operator != ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_not_equal_optional_none __GO_TO__]``
+
+    template<class T> inline optional<T> make_optional ( T const& v ) ; ``[link reference_make_optional_value __GO_TO__]``
+
+    template<class T> inline optional<T> make_optional ( bool condition, T const& v ) ; ``[link reference_make_optional_bool_value __GO_TO__]``
+
+    template<class T> inline auto get_optional_value_or ( optional<T> const& opt, typename optional<T>::reference_const_type def ) -> typename optional<T>::reference_const_type; ``[link reference_free_get_value_or __GO_TO__]`` 
+    
+    template<class T> inline auto get_optional_value_or ( optional<T> const& opt, typename optional<T>::reference_type def ) -> typename optional<T>::reference_type ; ``[link reference_free_get_value_or __GO_TO__]``
+
+    template<class T> inline T const& get ( optional<T> const& opt ) ; ``[link reference_optional_get __GO_TO__]``
+
+    template<class T> inline T& get ( optional<T> & opt ) ; ``[link reference_optional_get __GO_TO__]``
+
+    template<class T> inline T const* get ( optional<T> const* opt ) ; ``[link reference_optional_get __GO_TO__]``
+
+    template<class T> inline T* get ( optional<T>* opt ) ; ``[link reference_optional_get __GO_TO__]``
+
+    template<class T> inline auto get_pointer ( optional<T> const& opt ) -> ``['see below]``; ``[link reference_free_get_pointer __GO_TO__]``
+
+    template<class T> inline auto get_pointer ( optional<T> & opt ) -> ``['see below]``; ``[link reference_free_get_pointer __GO_TO__]``
+
+    template<class T> inline void swap( optional<T>& x, optional<T>& y ) ; ``[link reference_swap_optional_optional __GO_TO__]``
+    
+    template<class T> inline void swap( optional<T&>& x, optional<T&>& y ) ; ``[link reference_swap_optional_reference __GO_TO__]``
+
+    } // namespace boost
+
+
+[endsect]
+
+
+[section:header_optional_optional_values Optional Values]
+
+[#reference_operator_template]
+    
     template <class T>
     class optional
     {
     public :
 
-        typedef T value_type;
+        typedef T         value_type ;
+        typedef T &       reference_type ;
+        typedef T const&  reference_const_type ;
+        typedef T &&      rval_reference_type ;
+        typedef T *       pointer_type ;
+        typedef T const*  pointer_const_type ;
         
-        // (If T is of reference type, the parameters and results by reference are by value)
-
         optional () noexcept ; ``[link reference_optional_constructor __GO_TO__]``
 
         optional ( none_t ) noexcept ; ``[link reference_optional_constructor_none_t __GO_TO__]``
@@ -61,7 +120,7 @@
         
         template<class U> optional& operator = ( optional<U>&& rhs ) ; ``[link reference_optional_operator_move_equal_other_optional __GO_TO__]``
         
-        template<class... Args> void emplace ( Args...&& args ) ; ``[link reference_optional_emplace __GO_TO__]``
+        template<class... Args> void emplace ( Args&&... args ) ; ``[link reference_optional_emplace __GO_TO__]``
 
         template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; ``[link reference_optional_operator_equal_factory __GO_TO__]``
 
@@ -109,43 +168,80 @@
         T const& get_value_or( T const& default ) const ; ``[link reference_optional_get_value_or_value __GO_TO__]`` 
     };
 
-    template<class T> inline bool operator == ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_equal_optional_optional __GO_TO__]``
-
-    template<class T> inline bool operator != ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_not_equal_optional_optional __GO_TO__]``
-
-    template<class T> inline bool operator <  ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_less_optional_optional __GO_TO__]``
-
-    template<class T> inline bool operator >  ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_greater_optional_optional __GO_TO__]``
-
-    template<class T> inline bool operator <= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_less_or_equal_optional_optional __GO_TO__]``
-
-    template<class T> inline bool operator >= ( optional<T> const& x, optional<T> const& y ) ; ``[link reference_operator_compare_greater_or_equal_optional_optional __GO_TO__]``
-    
-    template<class T> inline bool operator == ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_equal_optional_none __GO_TO__]``
-
-    template<class T> inline bool operator != ( optional<T> const& x, none_t ) noexcept ; ``[link reference_operator_compare_not_equal_optional_none __GO_TO__]``
-
-    template<class T> inline optional<T> make_optional ( T const& v ) ; ``[link reference_make_optional_value __GO_TO__]``
-
-    template<class T> inline optional<T> make_optional ( bool condition, T const& v ) ; ``[link reference_make_optional_bool_value __GO_TO__]``
-
-    template<class T> inline T const& get_optional_value_or ( optional<T> const& opt, T const& default ) ; ``[link reference_optional_get_value_or_value __GO_TO__]`` 
-
-    template<class T> inline T const& get ( optional<T> const& opt ) ; ``[link reference_optional_get __GO_TO__]``
-
-    template<class T> inline T& get ( optional<T> & opt ) ; ``[link reference_optional_get __GO_TO__]``
-
-    template<class T> inline T const* get ( optional<T> const* opt ) ; ``[link reference_optional_get __GO_TO__]``
-
-    template<class T> inline T* get ( optional<T>* opt ) ; ``[link reference_optional_get __GO_TO__]``
-
-    template<class T> inline T const* get_pointer ( optional<T> const& opt ) ; ``[link reference_optional_get_ptr __GO_TO__]``
-
-    template<class T> inline T* get_pointer ( optional<T> & opt ) ; ``[link reference_optional_get_ptr __GO_TO__]``
-
-    template<class T> inline void swap( optional<T>& x, optional<T>& y ) ; ``[link reference_swap_optional_optional __GO_TO__]``
-
-    } // namespace boost
-
 
 [endsect]
+
+
+[section:header_optional_optional_refs Optional References]
+
+[#reference_operator_template_spec]
+    template <class T>
+    class optional<T&> // specilization for lvalue references
+    {
+    public :
+
+        typedef T& value_type;
+        typedef T& reference_type;
+        typedef T& reference_const_type; // no const propagation
+        typedef T& rval_reference_type;
+        typedef T* pointer_type;
+        typedef T* pointer_const_type;   // no const propagation
+
+        optional () noexcept ; ``[link reference_optional_ref_default_ctor __GO_TO__]``
+
+        optional ( none_t ) noexcept ; ``[link reference_optional_ref_default_ctor __GO_TO__]``
+
+        template<class R> optional(R&& r) noexcept ;  ``[link reference_optional_ref_value_ctor __GO_TO__]``
+        
+        template <class R> optional(bool cond, R&& r) noexcept ; ``[link reference_optional_ref_cond_value_ctor __GO_TO__]``
+        
+        optional ( optional const& rhs ) noexcept ; ``[link reference_optional_ref_copy_ctor __GO_TO__]``
+
+        template<class U> explicit optional ( optional<U&> const& rhs ) noexcept ; ``[link reference_optional_ref_ctor_from_opt_U __GO_TO__]``
+
+        optional& operator = ( none_t ) noexcept ; ``[link reference_optional_ref_assign_none_t __GO_TO__]``
+
+
+        optional& operator = ( optional const& rhs ) noexcept; ``[link reference_optional_ref_copy_assign __GO_TO__]``
+
+        template<class U> optional& operator = ( optional<U&> const& rhs ) noexcept ; ``[link reference_optional_ref_assign_optional_U __GO_TO__]``
+          
+        template<class R> optional& operator = (R&& r) noexcept ; ``[link reference_optional_ref_assign_R __GO_TO__]``      
+        
+        template<class R> void emplace ( R&& r ) noexcept ; ``[link reference_optional_ref_emplace_R __GO_TO__]``
+
+        T& get() const ; ``[link reference_optional_ref_get __GO_TO__]``
+        T& operator *() const ; ``[link reference_optional_ref_get __GO_TO__]``
+
+        T* operator ->() const ; ``[link reference_optional_ref_arrow __GO_TO__]``
+
+        T& value() const& ; ``[link reference_optional_ref_value __GO_TO__]``
+        
+        template<class R> T& value_or( R && r ) const noexcept ; ``[link reference_optional_ref_value_or __GO_TO__]``
+        
+        template<class F> T& value_or_eval( F f ) const ; ``[link reference_optional_ref_value_or_eval __GO_TO__]``
+
+        T* get_ptr() const noexcept ; ``[link reference_optional_ref_get_ptr __GO_TO__]``
+
+        explicit operator bool() const noexcept ; ``[link reference_optional_ref_operator_bool __GO_TO__]``
+
+        bool operator!() const noexcept ; ``[link reference_optional_ref_operator_not __GO_TO__]``
+
+        // deprecated methods
+
+        // (deprecated)
+        void reset() noexcept ; ``[link reference_optional_ref_reset __GO_TO__]``
+
+        // (deprecated)
+        template<class R> void reset ( R && r ) noexcept ; ``[link reference_optional_ref_reset_value __GO_TO__]``
+
+        // (deprecated)
+        bool is_initialized() const noexcept ; ``[link reference_optional_ref_is_initialized __GO_TO__]``
+
+        // (deprecated)
+        template<class R> T& get_value_or( R && r ) constnoexcept; ``[link reference_optional_ref_get_value_or_value __GO_TO__]`` 
+        
+    private:
+        T* ref; // exposition only
+    };
+[endsect]

doc/28_ref_optional_semantics.qbk

@@ -9,18 +9,7 @@
 ]
 
 
-[section Detailed Semantics]
-
-Because `T` might be of reference type, in the sequel, those entries whose
-semantic depends on `T` being of reference type or not will be distinguished
-using the following convention:
-
-* If the entry reads: `optional<T`['(not a ref)]`>`, the description
-corresponds only to the case where `T` is not of reference type.
-* If the entry reads: `optional<T&>`, the description corresponds only to
-the case where `T` is of reference type.
-* If the entry reads: `optional<T>`, the description is the same for both
-cases.
+[section Detailed Semantics - Optional Values]
 
 [note
 The following section contains various `assert()` which are used only to show
@@ -29,9 +18,6 @@ support each particular expression but that if the expression is supported,
 the implied condition holds.
 ]
 
-__SPACE__
-
-[heading optional class member functions]
 
 __SPACE__
 
@@ -70,7 +56,7 @@ __SPACE__
 
 [#reference_optional_constructor_value]
 
-[: `optional<T `['(not a ref)]`>::optional( T const& v )`]
+[: `optional<T>::optional( T const& v )`]
 
 * [*Requires:] `is_copy_constructible<T>::value` is `true`.
 * [*Effect:] Directly-Constructs an `optional`.
@@ -87,29 +73,12 @@ optional<T> opt(v);
 assert ( *opt == v ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>::optional( T& ref )`]
-
-* [*Effect:] Directly-Constructs an `optional`.
-* [*Postconditions:] `*this` is [_initialized] and its value is an instance
-of an internal type wrapping the reference `ref`.
-* [*Throws:] Nothing.
-* [*Example:]
-``
-T v;
-T& vref = v ;
-optional<T&> opt(vref);
-assert ( *opt == v ) ;
-++ v ; // mutate referee
-assert (*opt == v);
-``
 
 __SPACE__
 
 [#reference_optional_constructor_move_value]
 
-[: `optional<T `['(not a ref)]`>::optional( T&& v )`]
+[: `optional<T>::optional( T&& v )`]
 
 * [*Requires:] `is_move_constructible<T>::value` is `true`.
 * [*Effect:] Directly-Move-Constructs an `optional`.
@@ -125,35 +94,27 @@ optional<T> opt(std::move(v1));
 assert ( *opt == v2 ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>::optional( T&& ref ) = delete`]
-
-* [*Notes:] This constructor is deleted
-
 
 __SPACE__
 
 [#reference_optional_constructor_bool_value]
 
-[: `optional<T` ['(not a ref)]`>::optional( bool condition, T const& v ) ;` ]
-[: `optional<T&>           ::optional( bool condition, T&       v ) ;` ]
+[: `optional<T>::optional( bool condition, T const& v ) ;` ]
 
 * If condition is true, same as:
 
-[: `optional<T` ['(not a ref)]`>::optional( T const& v )`]
-[: `optional<T&>           ::optional( T&       v )`]
+[: `optional<T>::optional( T const& v )`]
 
 * otherwise, same as:
 
-[: `optional<T `['(not a ref)]`>::optional()`]
-[: `optional<T&>           ::optional()`]
+[: `optional<T>::optional()`]
+
 
 __SPACE__
 
 [#reference_optional_constructor_optional]
 
-[: `optional<T `['(not a ref)]`>::optional( optional const& rhs );`]
+[: `optional<T>::optional( optional const& rhs );`]
 
 * [*Requires:] `is_copy_constructible<T>::value` is `true`.
 * [*Effect:] Copy-Constructs an `optional`.
@@ -178,43 +139,12 @@ optional<T> init2 ( init ) ;
 assert ( init2 == init ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>::optional( optional const& rhs );`]
-
-* [*Effect:] Copy-Constructs an `optional`.
-* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
-value is another reference to the same object referenced by `*rhs`; else
-`*this` is uninitialized.
-* [*Throws:] Nothing.
-* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will refer to the
-same object (they alias).
-* [*Example:]
-``
-optional<T&> uninit ;
-assert (!uninit);
-
-optional<T&> uinit2 ( uninit ) ;
-assert ( uninit2 == uninit );
-
-T v = 2 ; T& ref = v ;
-optional<T> init(ref);
-assert ( *init == v ) ;
-
-optional<T> init2 ( init ) ;
-assert ( *init2 == v ) ;
-
-v = 3 ;
-
-assert ( *init  == 3 ) ;
-assert ( *init2 == 3 ) ;
-``
 
 __SPACE__
 
 [#reference_optional_move_constructor_optional]
 
-[: `optional<T `['(not a ref)]`>::optional( optional&& rhs ) noexcept(`['see below]`);`]
+[: `optional<T>::optional( optional&& rhs ) noexcept(`['see below]`);`]
 
 * [*Requires:] `is_move_constructible<T>::value` is `true`.
 * [*Effect:] Move-constructs an `optional`.
@@ -243,43 +173,12 @@ assert ( init2 );
 assert ( **init2 == T(2) ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>::optional( optional && rhs );`]
-
-* [*Effect:] Move-Constructs an `optional`.
-* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
-value is another reference to the same object referenced by `*rhs`; else
-`*this` is uninitialized.
-* [*Throws:] Nothing.
-* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will refer to the
-same object (they alias).
-* [*Example:]
-``
-optional<std::unique_ptr<T>&> uninit ;
-assert (!uninit);
-
-optional<std::unique_ptr<T>&> uinit2 ( std::move(uninit) ) ;
-assert ( uninit2 == uninit );
-
-std::unique_ptr<T> v(new T(2)) ;
-optional<std::unique_ptr<T>&> init(v);
-assert ( *init == v ) ;
-
-optional<std::unique_ptr<T>&> init2 ( std::move(init) ) ;
-assert ( *init2 == v ) ;
-
-*v = 3 ;
-
-assert ( **init  == 3 ) ;
-assert ( **init2 == 3 ) ;
-``
 
 __SPACE__
 
 [#reference_optional_constructor_other_optional]
 
-[: `template<U> explicit optional<T` ['(not a ref)]`>::optional( optional<U> const& rhs );`]
+[: `template<U> explicit optional<T>::optional( optional<U> const& rhs );`]
 
 * [*Effect:] Copy-Constructs an `optional`.
 * [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
@@ -303,7 +202,7 @@ __SPACE__
 
 [#reference_optional_move_constructor_other_optional]
 
-[: `template<U> explicit optional<T` ['(not a ref)]`>::optional( optional<U>&& rhs );`]
+[: `template<U> explicit optional<T>::optional( optional<U>&& rhs );`]
 
 * [*Effect:] Move-constructs an `optional`.
 * [*Postconditions:] If `rhs` is initialized, `*this` is initialized and its
@@ -327,8 +226,8 @@ __SPACE__
 
 [#reference_optional_constructor_factory]
 
-[: `template<InPlaceFactory> explicit optional<T` ['(not a ref)]`>::optional( InPlaceFactory const& f );`]
-[: `template<TypedInPlaceFactory> explicit optional<T` ['(not a ref)]`>::optional( TypedInPlaceFactory const& f );`]
+[: `template<InPlaceFactory> explicit optional<T>::optional( InPlaceFactory const& f );`]
+[: `template<TypedInPlaceFactory> explicit optional<T>::optional( TypedInPlaceFactory const& f );`]
 
 * [*Effect:] Constructs an `optional` with a value of `T` obtained from the
 factory.
@@ -365,7 +264,7 @@ __SPACE__
 
 [#reference_optional_operator_equal_value]
 
-[: `optional& optional<T` ['(not a ref)]`>::operator= ( T const& rhs ) ;`]
+[: `optional& optional<T>::operator= ( T const& rhs ) ;`]
 
 * [*Effect:] Assigns the value `rhs` to an `optional`.
 * [*Postconditions: ] `*this` is initialized and its value is a ['copy] of `rhs`.
@@ -390,40 +289,12 @@ opt = y ;
 assert ( *opt == y ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>& optional<T&>::operator= ( T& rhs ) ;`]
-
-* [*Effect:] (Re)binds the wrapped reference.
-* [*Postconditions: ] `*this` is initialized and it references the same
-object referenced by `rhs`.
-* [*Notes:] If `*this` was initialized, it is ['rebound] to the new object.
-See [link boost_optional.tutorial.rebinding_semantics_for_assignment_of_optional_references here] for details on this behavior.
-* [*Example:]
-``
-int a = 1 ;
-int b = 2 ;
-T& ra = a ;
-T& rb = b ;
-optional<int&> def ;
-optional<int&> opt(ra) ;
-
-def = rb ; // binds 'def' to 'b' through 'rb'
-assert ( *def == b ) ;
-*def = a ; // changes the value of 'b' to a copy of the value of 'a'
-assert ( b == a ) ;
-int c = 3;
-int& rc = c ;
-opt = rc ; // REBINDS to 'c' through 'rc'
-c = 4 ;
-assert ( *opt == 4 ) ;
-``
 
 __SPACE__
 
 [#reference_optional_operator_move_equal_value]
 
-[: `optional& optional<T` ['(not a ref)]`>::operator= ( T&& rhs ) ;`]
+[: `optional& optional<T>::operator= ( T&& rhs ) ;`]
 
 * [*Effect:] Moves the value `rhs` to an `optional`.
 * [*Postconditions: ] `*this` is initialized and its value is moved from `rhs`.
@@ -448,18 +319,12 @@ opt = std::move(y2) ;
 assert ( *opt == yR ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&>& optional<T&>::operator= ( T&& rhs ) = delete;`]
-
-* [*Notes:] This assignment operator is deleted.
-
 
 __SPACE__
 
 [#reference_optional_operator_equal_optional]
 
-[: `optional& optional<T` ['(not a ref)]`>::operator= ( optional const& rhs ) ;`]
+[: `optional& optional<T>::operator= ( optional const& rhs ) ;`]
 
 * [*Requires:] `T` is __COPY_CONSTRUCTIBLE__ and `CopyAssignable`.
 * [*Effects:]
@@ -485,43 +350,12 @@ assert ( !def ) ;
 // previous value (copy of 'v') destroyed from within 'opt'.
 ``
 
-__SPACE__
-
-[: `optional<T&> & optional<T&>::operator= ( optional<T&> const& rhs ) ;`]
-
-* [*Effect:] (Re)binds thee wrapped reference.
-* [*Postconditions:] If `*rhs` is initialized, `*this` is initialized and it
-references the same object referenced by `*rhs`; otherwise, `*this` is
-uninitialized (and references no object).
-* [*Notes:] If `*this` was initialized and so is `*rhs`, `*this` is ['rebound] to
-the new object. See [link boost_optional.tutorial.rebinding_semantics_for_assignment_of_optional_references here] for details on this behavior.
-* [*Example:]
-``
-int a = 1 ;
-int b = 2 ;
-T& ra = a ;
-T& rb = b ;
-optional<int&> def ;
-optional<int&> ora(ra) ;
-optional<int&> orb(rb) ;
-
-def = orb ; // binds 'def' to 'b' through 'rb' wrapped within 'orb'
-assert ( *def == b ) ;
-*def = ora ; // changes the value of 'b' to a copy of the value of 'a'
-assert ( b == a ) ;
-int c = 3;
-int& rc = c ;
-optional<int&> orc(rc) ;
-ora = orc ; // REBINDS ora to 'c' through 'rc'
-c = 4 ;
-assert ( *ora == 4 ) ;
-``
 
 __SPACE__
 
 [#reference_optional_operator_move_equal_optional]
 
-[: `optional& optional<T` ['(not a ref)]`>::operator= ( optional&& rhs ) noexcept(`['see below]`);`]
+[: `optional& optional<T>::operator= ( optional&& rhs ) noexcept(`['see below]`);`]
 
 * [*Requires:] `T` is __MOVE_CONSTRUCTIBLE__ and `MoveAssignable`.
 * [*Effects:]
@@ -548,18 +382,13 @@ assert ( opt ) ;
 assert ( *opt == T(2) ) ;
 ``
 
-__SPACE__
-
-[: `optional<T&> & optional<T&>::operator= ( optional<T&>&& rhs ) ;`]
-
-* [*Effect:] Same as `optional<T&>::operator= ( optional<T&> const& rhs )`.
 
 __SPACE__
 
 
 [#reference_optional_operator_equal_other_optional]
 
-[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U> const& rhs ) ;`]
+[: `template<U> optional& optional<T>::operator= ( optional<U> const& rhs ) ;`]
 
 * [*Effect:] 
 [table 
@@ -587,7 +416,7 @@ __SPACE__
 
 [#reference_optional_operator_move_equal_other_optional]
 
-[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U>&& rhs ) ;`]
+[: `template<U> optional& optional<T>::operator= ( optional<U>&& rhs ) ;`]
 
 * [*Effect:]
 [table
@@ -617,7 +446,7 @@ __SPACE__
 
 [#reference_optional_emplace]
 
-[: `template<class... Args> void optional<T` ['(not a ref)]`>::emplace( Args...&& args );`]
+[: `template<class... Args> void optional<T>::emplace( Args&&... args );`]
 
 * [*Requires:] The compiler supports rvalue references and variadic templates.
 * [*Effect:] If `*this` is initialized calls `*this = none`.
@@ -642,8 +471,8 @@ __SPACE__
 
 [#reference_optional_operator_equal_factory]
 
-[: `template<InPlaceFactory> optional<T>& optional<T` ['(not a ref)]`>::operator=( InPlaceFactory const& f );`]
-[: `template<TypedInPlaceFactory> optional<T>& optional<T` ['(not a ref)]`>::operator=( TypedInPlaceFactory const& f );`]
+[: `template<InPlaceFactory> optional<T>& optional<T>::operator=( InPlaceFactory const& f );`]
+[: `template<TypedInPlaceFactory> optional<T>& optional<T>::operator=( TypedInPlaceFactory const& f );`]
 
 * [*Effect:] Assigns an `optional` with a value of `T` obtained from the
 factory.
@@ -659,7 +488,7 @@ __SPACE__
 
 [#reference_optional_reset_value]
 
-[: `void optional<T` ['(not a ref)]`>::reset( T const& v ) ;`]
+[: `void optional<T>::reset( T const& v ) ;`]
 * [*Deprecated:] same as `operator= ( T const& v) ;`
 
 __SPACE__
@@ -673,36 +502,24 @@ __SPACE__
 
 [#reference_optional_get]
 
-[: `T const& optional<T` ['(not a ref)]`>::get() const ;`]
-[: `T&       optional<T` ['(not a ref)]`>::get() ;`]
+[: `T const& optional<T>::get() const ;`]
+[: `T&       optional<T>::get() ;`]
 
-[: `inline T const& get ( optional<T` ['(not a ref)]`> const& ) ;`]
-[: `inline T&       get ( optional<T` ['(not a ref)]`> &) ;`]
+[: `inline T const& get ( optional<T> const& ) ;`]
+[: `inline T&       get ( optional<T> &) ;`]
 
 * [*Requires:] `*this` is initialized
 * [*Returns:] A reference to the contained value
 * [*Throws:] Nothing.
 * [*Notes:] The requirement is asserted via `BOOST_ASSERT()`.
 
-__SPACE__
-
-[: `T const& optional<T&>::get() const ;`]
-[: `T&       optional<T&>::get() ;`]
-
-[: `inline T const& get ( optional<T&> const& ) ;`]
-[: `inline T&       get ( optional<T&> &) ;`]
-
-* [*Requires: ] `*this` is initialized
-* [*Returns:] [_The] reference contained.
-* [*Throws:] Nothing.
-* [*Notes:] The requirement is asserted via `BOOST_ASSERT()`.
 
 __SPACE__
 
 [#reference_optional_operator_asterisk]
 
-[: `T const& optional<T` ['(not a ref)]`>::operator*() const& ;`]
-[: `T&       optional<T` ['(not a ref)]`>::operator*() &;`]
+[: `T const& optional<T>::operator*() const& ;`]
+[: `T&       optional<T>::operator*() &;`]
 
 * [*Requires:] `*this` is initialized
 * [*Returns:] A reference to the contained value
@@ -723,32 +540,12 @@ __SPACE__
 
 [#reference_optional_operator_asterisk_move]
 
-[: `T&& optional<T` ['(not a ref)]`>::operator*() &&;`]
+[: `T&& optional<T>::operator*() &&;`]
 
 * [*Requires:] `*this` contains a value.
 * [*Effects:] Equivalent to `return std::move(*val);`.
 * [*Notes:] The requirement is asserted via `BOOST_ASSERT()`. On compilers that do not support ref-qualifiers on member functions this overload is not present.
 
-__SPACE__
-
-[: `T & optional<T&>::operator*() const& ;`]
-[: `T & optional<T&>::operator*() & ;`]
-[: `T & optional<T&>::operator*() && ;`]
-
-* [*Requires: ] `*this` is initialized
-* [*Returns:] [_The] reference contained.
-* [*Throws:] Nothing.
-* [*Notes:] The requirement is asserted via `BOOST_ASSERT()`. On compilers that do not support ref-qualifiers on member functions these three overloads are replaced with the classical two: a `const` and non-`const` member functions.
-* [*Example:]
-``
-T v ;
-T& vref = v ;
-optional<T&> opt ( vref );
-T const& vref2 = *opt;
-assert ( vref2 == v ) ;
-++ v ;
-assert ( *opt == v ) ;
-``
 
 __SPACE__
 
@@ -845,11 +642,8 @@ __SPACE__
 
 [#reference_optional_get_value_or_value]
 
-[: `T const& optional<T` ['(not a ref)]`>::get_value_or( T const& default) const ;`]
-[: `T&       optional<T` ['(not a ref)]`>::get_value_or( T&       default ) ;`]
-
-[: `inline T const& get_optional_value_or ( optional<T` ['(not a ref)]`> const& o, T const& default ) ;`]
-[: `inline T&       get_optional_value_or ( optional<T` ['(not a ref)]`>&       o, T&       default ) ;`]
+[: `T const& optional<T>::get_value_or( T const& default) const ;`]
+[: `T&       optional<T>::get_value_or( T&       default ) ;`]
 
 * [*Deprecated:] Use `value_or()` instead.
 * [*Returns:] A reference to the contained value, if any, or `default`.
@@ -862,7 +656,7 @@ T const& y = def.get_value_or(z);
 assert ( y == z ) ;
 
 optional<T> opt ( v );
-T const& u = get_optional_value_or(opt,z);
+T const& u = opt.get_value_or(z);
 assert ( u == v ) ;
 assert ( u != z ) ;
 ``
@@ -872,11 +666,8 @@ __SPACE__
 
 [#reference_optional_get_ptr]
 
-[: `T const* optional<T` ['(not a ref)]`>::get_ptr() const ;`]
-[: `T*       optional<T` ['(not a ref)]`>::get_ptr() ;`]
-
-[: `inline T const* get_pointer ( optional<T` ['(not a ref)]`> const& ) ;`]
-[: `inline T*       get_pointer ( optional<T` ['(not a ref)]`> &) ;`]
+[: `T const* optional<T>::get_ptr() const ;`]
+[: `T*       optional<T>::get_ptr() ;`]
 
 * [*Returns:] If `*this` is initialized, a pointer to the contained value;
 else `0` (['null]).
@@ -898,8 +689,8 @@ __SPACE__
 
 [#reference_optional_operator_arrow]
 
-[: `T const* optional<T` ['(not a ref)]`>::operator ->() const ;`]
-[: `T*       optional<T` ['(not a ref)]`>::operator ->()       ;`]
+[: `T const* optional<T>::operator ->() const ;`]
+[: `T*       optional<T>::operator ->()       ;`]
 
 * [*Requires: ] `*this` is initialized.
 * [*Returns:] A pointer to the contained value.
@@ -957,15 +748,301 @@ __SPACE__
 
 * [*Deprecated:] Same as `explicit operator bool () ;`
 
+
+[endsect]
+
+[section Detailed Semantics - Optional References]
+
 __SPACE__
 
-[heading Free functions]
+[#reference_optional_ref_default_ctor]
+
+[: `optional<T&>::optional() noexcept;`]
+[: `optional<T&>::optional(none_t) noexcept;`]
+
+* [*Postconditions:] `bool(*this) == false`; `*this` refers to nothing.
+
+
+__SPACE__
+
+[#reference_optional_ref_value_ctor]
+
+[: `template<class R> optional<T&>::optional(R&& r) noexcept;`]
+* [*Postconditions:] `bool(*this) == true`; `addressof(**this) == addressof(r)`.
+* [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed. This constructor does not participate in overload resolution if `decay<R>` is an instance of `boost::optional`.
+* [*Notes:] This constructor is declared `explicit` on compilers that do not correctly suport binding to const lvalues of integral types. For more details [link optional_reference_binding see here]. 
+* [*Example:]
+``
+T v;
+T& vref = v ;
+optional<T&> opt(vref);
+assert ( *opt == v ) ;
+++ v ; // mutate referee
+assert (*opt == v);
+``
+
+__SPACE__
+
+[#reference_optional_ref_cond_value_ctor]
+
+[: `template<class R> optional<T&>::optional(bool cond, R&& r) noexcept;`]
+* [*Effects: ] Initializes `ref` with expression `cond ? addressof(r) : nullptr`.
+* [*Postconditions:] `bool(*this) == cond`; If `bool(*this)`, `addressof(**this) == addressof(r)`.
+* [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed. This constructor does not participate in overload resolution if `decay<R>` is an instance of `boost::optional`.
+
+__SPACE__
+
+[#reference_optional_ref_copy_ctor]
+
+[: `optional<T&>::optional ( optional const& rhs ) noexcept ;`]
+
+* [*Effects: ] Initializes `ref` with expression `rhs.ref`.
+ 
+* [*Postconditions:] `bool(*this) == bool(rhs)`.
+
+* [*Example:]
+``
+optional<T&> uninit ;
+assert (!uninit);
+
+optional<T&> uinit2 ( uninit ) ;
+assert ( uninit2 == uninit );
+
+T v = 2 ; T& ref = v ;
+optional<T> init(ref);
+assert ( *init == v ) ;
+
+optional<T> init2 ( init ) ;
+assert ( *init2 == v ) ;
+
+v = 3 ;
+
+assert ( *init  == 3 ) ;
+assert ( *init2 == 3 ) ;
+``
+
+__SPACE__
+
+[#reference_optional_ref_ctor_from_opt_U]
+
+[: `template<class U> explicit optional<T&>::optional ( optional<U&> const& rhs ) noexcept ;`]
+
+* [*Requires:] `is_convertible<U&, T&>::value` is `true`.
+
+* [*Effects: ] Initializes `ref` with expression `rhs.ref`.
+ 
+* [*Postconditions:] `bool(*this) == bool(rhs)`.
+
+
+__SPACE__
+
+[#reference_optional_ref_assign_none_t]
+
+[: `optional<T&>::operator= ( none_t ) noexcept ;`]
+
+* [*Effects: ] Assigns `ref` with expression `nullptr`.
+
+* [*returns:] `*this`.
+
+* [*Postconditions:] `bool(*this) == false`.
+
+ 
+
+[#reference_optional_ref_copy_assign]
+
+[: `optional& optional<T&>::operator= ( optional const& rhs ) noexcept ;`]
+
+* [*Effects: ] Assigns `ref` with expression `rhs.ref`.
+
+* [*returns:] `*this`.
+
+* [*Postconditions:] `bool(*this) == bool(rhs)`.
+
+* [*Notes:] This behaviour is called ['rebinding semantics]. See [link boost_optional.tutorial.optional_references.rebinding_semantics_for_assignment_of_optional_references here] for details.
+
+* [*Example:]
+``
+int a = 1 ;
+int b = 2 ;
+T& ra = a ;
+T& rb = b ;
+optional<int&> def ;
+optional<int&> ora(ra) ;
+optional<int&> orb(rb) ;
+
+def = orb ; // binds 'def' to 'b' through 'rb' wrapped within 'orb'
+assert ( *def == b ) ;
+*def = ora ; // changes the value of 'b' to a copy of the value of 'a'
+assert ( b == a ) ;
+int c = 3;
+int& rc = c ;
+optional<int&> orc(rc) ;
+ora = orc ; // REBINDS ora to 'c' through 'rc'
+c = 4 ;
+assert ( *ora == 4 ) ;
+``
+
+
+[#reference_optional_ref_assign_optional_U]
+
+[: `template<class U> optional& optional<T&>::operator= ( optional<U&> const& rhs ) noexcept ;`]
+
+* [*Requires:] `is_convertible<U&, T&>::value` is `true`.
+
+* [*Effects: ] Assigns `ref` with expression `rhs.ref`.
+
+* [*returns:] `*this`.
+
+* [*Postconditions:] `bool(*this) == bool(rhs)`.
+   
+
+__SPACE__
+
+[#reference_optional_ref_assign_R]
+
+[: `template<class R> optional& optional<T&>::operator= ( R&& r ) noexcept ;`]
+
+* [*Effects: ] Assigns `ref` with expression `r`.
+
+* [*returns:] `*this`.
+ 
+* [*Postconditions:] `bool(*this) == true`.
+
+* [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed. This function does not participate in overload resolution if `decay<R>` is an instance of `boost::optional`.
+
+* [*Example:]
+``
+int a = 1 ;
+int b = 2 ;
+T& ra = a ;
+T& rb = b ;
+optional<int&> def ;
+optional<int&> opt(ra) ;
+
+def = rb ; // binds 'def' to 'b' through 'rb'
+assert ( *def == b ) ;
+*def = a ; // changes the value of 'b' to a copy of the value of 'a'
+assert ( b == a ) ;
+int c = 3;
+int& rc = c ;
+opt = rc ; // REBINDS to 'c' through 'rc'
+c = 4 ;
+assert ( *opt == 4 ) ;
+``
+
+__SPACE__
+
+[#reference_optional_ref_emplace_R]
+
+[: `void optional<T&>::emplace( R&& r ) noexcept ;`]
+* [*Effects: ] Assigns `ref` with expression `r`.
+* [*Postconditions:] `bool(*this) == true`.
+* [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed. This function does not participate in overload resolution if `decay<R>` is an instance of `boost::optional`.
+
+__SPACE__
+
+[#reference_optional_ref_get]
+[: `T& optional<T&>::get() const ;`]
+[: `T& optional<T&>::operator *() const ;`]
+* [*Requires:] `bool(*this) == true`.
+* [*Effects: ] Returns `*ref`.
+* [*Throws: ] Nothing.
+* [*Example:]
+``
+T v ;
+T& vref = v ;
+optional<T&> opt ( vref );
+T const& vref2 = *opt;
+assert ( vref2 == v ) ;
+++ v ;
+assert ( *opt == v ) ;
+``
+
+__SPACE__
+
+[#reference_optional_ref_arrow]
+[: `T* optional<T&>::operator -> () const ;`]
+* [*Requires:] `bool(*this) == true`.
+* [*Effects: ] Returns `ref`.
+* [*Throws: ] Nothing.
+
+__SPACE__
+
+[#reference_optional_ref_value]
+[: `T& optional<T&>::value() const ;`]
+* [*Effects:] Equivalent to `return bool(*this) ? *val : throw bad_optional_access();`. 
+
+__SPACE__
+
+[#reference_optional_ref_value_or]
+[: `template<class R> T& optional<T&>::value_or( R&& r ) const noexcept;`]
+* [*Effects:] Equivalent to `if (*this) return **this; else return r;`. 
+* [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed.
+
+__SPACE__
+
+[#reference_optional_ref_value_or_eval]
+[: `template<class F> T& optional<T&>::value_or( F f ) const ;`]
+* [*Effects:] Equivalent to `if (*this) return **this; else return f();`.
+* [*Remarks:] Unless `decltype(f())` is an lvalue reference, the program is ill-formed.
+
+__SPACE__
+
+[#reference_optional_ref_get_ptr]
+[: `T* optional<T&>::get_ptr () const noexcept;`]
+* [*Returns:] `ref`.
+
+__SPACE__
+
+[#reference_optional_ref_operator_bool]
+[: `optional<T&>::operator bool () const noexcept;`]
+* [*Returns:] `bool(ref)`.
+
+__SPACE__
+
+[#reference_optional_ref_operator_not]
+[: `optional<T&>::operator ! () const noexcept;`]
+* [*Returns:] `!bool(ref)`.
+
+__SPACE__
+
+[#reference_optional_ref_reset]
+[: `void optional<T&>::reset() noexcept;`]
+* [*Effects:] Use `*this = none` instead.
+* [*Remarks:] This function is depprecated.
+
+__SPACE__
+
+[#reference_optional_ref_reset_value]
+[: `template<class R> void optional<T&>::reset ( R&& r) noexcept;`]
+* [*Effects:] Equivalent to `*this = std::forward<R>(r)`.
+* [*Remarks:] This function is depprecated.
+
+__SPACE__
+
+[#reference_optional_ref_is_initialized]
+[: `bool optional<T&>::is_initialized() const noexcept;`]
+* [*Effects:] Equivalent to `return bool(*this)`.
+* [*Remarks:] This function is depprecated.
+
+__SPACE__
+
+[#reference_optional_ref_get_value_or_value]
+[: `template<class R> T& optional<T&>::get_value_or( R&& r ) const noexcept;`]
+* [*Effects:] Equivalent to `return value_or(std::forward<R>(r);`. 
+* [*Remarks:] This function is depprecated.
+  
+[endsect]
+
+
+[section Detailed Semantics - Free Functions]
+
 
 __SPACE__
 
 [#reference_make_optional_value]
 
-[: `optional<T` ['(not a ref)]`> make_optional( T const& v )`]
+[: `optional<T> make_optional( T const& v )`]
 
 * [*Returns: ] `optional<T>(v)` for the ['deduced] type `T` of `v`.
 * [*Example:]
@@ -979,9 +1056,9 @@ __SPACE__
 
 [#reference_make_optional_bool_value]
 
-[: `optional<T` ['(not a ref)]`> make_optional( bool condition, T const& v )`]
+[: `optional<T> make_optional( bool condition, T const& v )`]
 
-* [*Returns: ] `optional<T>(condition,v)` for the ['deduced] type `T` of `v`.
+* [*Returns: ] `optional<T>(condition, v)` for the ['deduced] type `T` of `v`.
 * [*Example:]
 ``
 optional<double> calculate_foo()
@@ -1105,9 +1182,28 @@ __SPACE__
 [: `bool operator != ( optional<T> const& x, none_t ) noexcept;`]
 [: `bool operator != ( none_t, optional<T> const& x ) noexcept;`]
 
-* [*Returns: ] `!( x == y );`
+* [*Returns: ] `bool(x);`
 
 
+__SPACE__
+
+
+[#reference_free_get_pointer]
+[: `auto get_pointer ( optional<T>& o ) -> typename optional<T>::pointer_type ;`]
+[: `auto get_pointer ( optional<T> const& o ) -> typename optional<T>::pointer_const_type ;`]
+* [*Returns:] `o.get_ptr()`.
+* [*Throws:] Nothing.
+
+__SPACE__
+
+
+[#reference_free_get_value_or]
+[: `auto get_optional_value_or ( optional<T>& o, typename optional<T>::reference_type def ) -> typename optional<T>::reference_type ;`]
+[: `auto get_optional_value_or ( optional<T> const& o, typename optional<T>::reference_const_type  def ) -> typename optional<T>::reference_const_type ;`]
+* [*Returns:] `o.get_value_or(def)`.
+* [*Throws:] Nothing.
+* [*Remarks:] This function is deprecated.
+
 __SPACE__
 
 [#reference_swap_optional_optional]
@@ -1147,4 +1243,30 @@ assert ( *optX == y );
 assert ( *optY == x );
 ``
 
+__SPACE__
+
+[#reference_swap_optional_reference]
+[: `void swap ( optional<T&>& x, optional<T&>& y ) noexcept ;`]
+
+* [*Postconditions:] `x` refers to what `y` refererred to before the swap (if anything). `y` refers to whatever `x` referred to before the swap.
+
+* [*Example:]
+``
+T x(12);
+T y(21);
+
+optional<T&> opt0;
+optional<T&> optX (x);
+optional<T&> optY (y);
+
+boost::swap(optX, optY);
+assert (addressof(*optX) == addressof(y));
+assert (addressof(*optY) == addressof(x));
+
+boost::swap(opt0, optX);
+assert ( opt0 );
+assert ( !optX );
+assert (addressof(*opt0) == addressof(y));
+``
+
 [endsect]

doc/90_dependencies.qbk

@@ -28,19 +28,19 @@ The implementation uses the following other Boost modules:
 [endsect]
 
 
-[section Optional Reference Binding]
+[section Optional Reference Binding][#optional_reference_binding]
 
-On compilers that do not conform to Standard C++ rules of reference binding, operations on optional references might give adverse results: rather than binding a reference to a designated object they may create an unexpected temporary and bind to it. Compilers known to have these deficiencies include GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0, 11.0, 12.0. On these compilers prefer using direct-initialization and copy assignment of optional references to copy-initialization and assignment from `T&`:
+A number of compilers incorrectly treat const lvalues of integral type as rvalues, and create an illegal temporary when binding to an lvalue reference to const in some expressions. This could result in creating an optional lvalue reference that is in fact bound to an unexpected temporary rather than to the intended object. In order to prevent hard to find run-time bugs, this library performs compile-time checks to prevent expressions that would otherwise bind an optional reference to an unexpected temporary. As a consequence, on certain compilers certain pieces of functionality in optional references are missing. In order to maintain a portability of your code across diferent compilers, it is recommended that you only stick to the minimum portable interface of optional references: prefer direct-initialization and copy assignment of optional references to copy-initialization and assignment from `T&`:
 
     const int i = 0;
     optional<const int&> or1;
-    optional<const int&> or2 = i;  // not portable
-    or1 = i;                       // not portable
+    optional<const int&> or2 = i;  // caution: not portable
+    or1 = i;                       // caution: not portable
     
     optional<const int&> or3(i);   // portable
     or1 = optional<const int&>(i); // portable
 
-In order to check if your compiler correctly implements reference binding use this test program. 
+Compilers known to have these deficiencies include GCC versions 4.2, 4.3, 4.4, 4.5, 5.1, 5.2; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0, 11.0, 12.0. In order to check if your compiler correctly implements reference binding use this test program. 
 
     #include <cassert>
 

doc/91_relnotes.qbk

@@ -1,7 +1,7 @@
 [/
     Boost.Optional
 
-    Copyright (c) 2015 Andrzej Krzemienski
+    Copyright (c) 2015, 2016 Andrzej Krzemienski
 
     Distributed under the Boost Software License, Version 1.0.
     (See accompanying file LICENSE_1_0.txt or copy at
@@ -11,11 +11,31 @@
 
 [section:relnotes Release Notes]
 
+
+[heading Boost Release 1.62]
+
+* Fixed [@https://svn.boost.org/trac/boost/ticket/12179 Trac #12179].
+
+
+[heading Boost Release 1.61]
+
+* Now `boost::optional` is specialized for reference parameters. This addresses a couple of issues:
+  * the `sizeof` of optional reference is that of a pointer,
+  * some bugs connected to copying optional references are gone,
+  * all run-time bugs caused by incorrect reference binding on some compilers are now turned into compile-time errors,
+  * you can swap optional references: it is like swapping pointers: shalow, underlying objects are not affected,
+  * optional references to abstract types work.
+* Documented nested typedefs ([@https://svn.boost.org/trac/boost/ticket/5193 Trac #5193]).
+* Made the perfect-forwarding constructor SFINAE-friendly, which fixes [@https://svn.boost.org/trac/boost/ticket/12002 Trac #12002]. However, this only works in the newer platforms that correctly implement C++11 `<type_traits>`.
+* Fixed [@https://svn.boost.org/trac/boost/ticket/10445 Trac #10445].
+
+
 [heading Boost Release 1.60]
 
 * Changed the implementation of `boost::none` again. Now it is a const object with internal linkage (as any other tag). This fixes [@https://svn.boost.org/trac/boost/ticket/11203 Trac #11203].
 
-[heading Boost Release 1.59]  
+
+[heading Boost Release 1.59]
 
 * For C++03 compilers, added 0-argument overload for member function `emplace()`, and therewith removed the dependency on `<boost/utility/in_place_factory.hpp>`.
 * Fixed [@https://svn.boost.org/trac/boost/ticket/11241 Trac #11241].

doc/html/boost_optional/acknowledgements.html

@@ -116,7 +116,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/dependencies_and_portability.html

@@ -75,7 +75,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/dependencies_and_portability/optional_reference_binding.html

@@ -28,24 +28,31 @@
       Reference Binding</a>
 </h3></div></div></div>
 <p>
-        On compilers that do not conform to Standard C++ rules of reference binding,
-        operations on optional references might give adverse results: rather than
-        binding a reference to a designated object they may create an unexpected
-        temporary and bind to it. Compilers known to have these deficiencies include
-        GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0,
-        11.0, 12.0. On these compilers prefer using direct-initialization and copy
-        assignment of optional references to copy-initialization and assignment from
-        <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>:
+        <a name="optional_reference_binding"></a>A number of compilers incorrectly
+        treat const lvalues of integral type as rvalues, and create an illegal temporary
+        when binding to an lvalue reference to const in some expressions. This could
+        result in creating an optional lvalue reference that is in fact bound to
+        an unexpected temporary rather than to the intended object. In order to prevent
+        hard to find run-time bugs, this library performs compile-time checks to
+        prevent expressions that would otherwise bind an optional reference to an
+        unexpected temporary. As a consequence, on certain compilers certain pieces
+        of functionality in optional references are missing. In order to maintain
+        a portability of your code across diferent compilers, it is recommended that
+        you only stick to the minimum portable interface of optional references:
+        prefer direct-initialization and copy assignment of optional references to
+        copy-initialization and assignment from <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>:
       </p>
 <pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
 <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or1</span><span class="special">;</span>
-<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or2</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>  <span class="comment">// not portable</span>
-<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>                       <span class="comment">// not portable</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or2</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>  <span class="comment">// caution: not portable</span>
+<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>                       <span class="comment">// caution: not portable</span>
 
 <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or3</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>   <span class="comment">// portable</span>
 <span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
 </pre>
 <p>
+        Compilers known to have these deficiencies include GCC versions 4.2, 4.3,
+        4.4, 4.5, 5.1, 5.2; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0, 11.0, 12.0.
         In order to check if your compiler correctly implements reference binding
         use this test program.
       </p>
@@ -86,7 +93,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/quick_start.html

@@ -155,7 +155,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/quick_start/bypassing_unnecessary_default_construction.html

@@ -61,7 +61,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/quick_start/optional_automatic_variables.html

@@ -61,7 +61,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/quick_start/optional_data_members.html

@@ -80,7 +80,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/quick_start/storage_in_containers.html

@@ -50,7 +50,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/acknowledgements.html

@@ -0,0 +1,131 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Acknowledgements</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="relnotes.html" title="Release Notes">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="relnotes.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.acknowledgements"></a><a class="link" href="acknowledgements.html" title="Acknowledgements">Acknowledgements</a>
+</h3></div></div></div>
+<h5>
+<a name="boost_optional.reference.acknowledgements.h0"></a>
+        <span class="phrase"><a name="boost_optional.reference.acknowledgements.pre_formal_review"></a></span><a class="link" href="acknowledgements.html#boost_optional.reference.acknowledgements.pre_formal_review">Pre-formal
+        review</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+            Peter Dimov suggested the name 'optional', and was the first to point
+            out the need for aligned storage.
+          </li>
+<li class="listitem">
+            Douglas Gregor developed 'type_with_alignment', and later Eric Friedman
+            coded 'aligned_storage', which are the core of the optional class implementation.
+          </li>
+<li class="listitem">
+            Andrei Alexandrescu and Brian Parker also worked with aligned storage
+            techniques and their work influenced the current implementation.
+          </li>
+<li class="listitem">
+            Gennadiy Rozental made extensive and important comments which shaped
+            the design.
+          </li>
+<li class="listitem">
+            Vesa Karvonen and Douglas Gregor made quite useful comparisons between
+            optional, variant and any; and made other relevant comments.
+          </li>
+<li class="listitem">
+            Douglas Gregor and Peter Dimov commented on comparisons and evaluation
+            in boolean contexts.
+          </li>
+<li class="listitem">
+            Eric Friedman helped understand the issues involved with aligned storage,
+            move/copy operations and exception safety.
+          </li>
+<li class="listitem">
+            Many others have participated with useful comments: Aleksey Gurotov,
+            Kevlin Henney, David Abrahams, and others I can't recall.
+          </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.acknowledgements.h1"></a>
+        <span class="phrase"><a name="boost_optional.reference.acknowledgements.post_formal_review"></a></span><a class="link" href="acknowledgements.html#boost_optional.reference.acknowledgements.post_formal_review">Post-formal
+        review</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+            William Kempf carefully considered the originally proposed interface
+            and suggested the new interface which is currently used. He also started
+            and fueled the discussion about the analogy optional&lt;&gt;/smart pointer
+            and about relational operators.
+          </li>
+<li class="listitem">
+            Peter Dimov, Joel de Guzman, David Abrahams, Tanton Gibbs and Ian Hanson
+            focused on the relational semantics of optional (originally undefined);
+            concluding with the fact that the pointer-like interface doesn't make
+            it a pointer so it shall have deep relational operators.
+          </li>
+<li class="listitem">
+            Augustus Saunders also explored the different relational semantics between
+            optional&lt;&gt; and a pointer and developed the OptionalPointee concept
+            as an aid against potential conflicts on generic code.
+          </li>
+<li class="listitem">
+            Joel de Guzman noticed that optional&lt;&gt; can be seen as an API on
+            top of variant&lt;T,nil_t&gt;.
+          </li>
+<li class="listitem">
+            Dave Gomboc explained the meaning and usage of the Haskell analog to
+            optional&lt;&gt;: the Maybe type constructor (analogy originally pointed
+            out by David Sankel).
+          </li>
+<li class="listitem">
+            Other comments were posted by Vincent Finn, Anthony Williams, Ed Brey,
+            Rob Stewart, and others.
+          </li>
+<li class="listitem">
+            Joel de Guzman made the case for the support of references and helped
+            with the proper semantics.
+          </li>
+<li class="listitem">
+            Mat Marcus shown the virtues of a value-oriented interface, influencing
+            the current design, and contributed the idea of "none".
+          </li>
+<li class="listitem">
+            Vladimir Batov's design of Boost.Convert library motivated the development
+            of value accessors for <code class="computeroutput"><span class="identifier">optional</span></code>:
+            functions <code class="computeroutput"><span class="identifier">value</span></code>, <code class="computeroutput"><span class="identifier">value_or</span></code>, <code class="computeroutput"><span class="identifier">value_or_eval</span></code>.
+          </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="relnotes.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/dependencies_and_portability.html

@@ -0,0 +1,84 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Dependencies and Portability</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">
+<link rel="next" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.dependencies_and_portability"></a><a class="link" href="dependencies_and_portability.html" title="Dependencies and Portability">Dependencies
+      and Portability</a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.dependencies_and_portability.dependencies"></a><a class="link" href="dependencies_and_portability.html#boost_optional.reference.dependencies_and_portability.dependencies" title="Dependencies">Dependencies</a>
+</h4></div></div></div>
+<p>
+          The implementation uses the following other Boost modules:
+        </p>
+<div class="orderedlist"><ol class="orderedlist" type="1">
+<li class="listitem">
+              assert
+            </li>
+<li class="listitem">
+              config
+            </li>
+<li class="listitem">
+              core
+            </li>
+<li class="listitem">
+              detail
+            </li>
+<li class="listitem">
+              move
+            </li>
+<li class="listitem">
+              mpl
+            </li>
+<li class="listitem">
+              static_assert
+            </li>
+<li class="listitem">
+              throw_exception
+            </li>
+<li class="listitem">
+              type_traits
+            </li>
+<li class="listitem">
+              utility
+            </li>
+</ol></div>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/dependencies_and_portability/optional_reference_binding.html

@@ -0,0 +1,100 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional Reference Binding</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+<link rel="prev" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+<link rel="next" href="../relnotes.html" title="Release Notes">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.dependencies_and_portability.optional_reference_binding"></a><a class="link" href="optional_reference_binding.html" title="Optional Reference Binding">Optional
+        Reference Binding</a>
+</h4></div></div></div>
+<p>
+          On compilers that do not conform to Standard C++ rules of reference binding,
+          operations on optional references might give adverse results: rather than
+          binding a reference to a designated object they may create an unexpected
+          temporary and bind to it. Compilers known to have these deficiencies include
+          GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0,
+          11.0, 12.0. On these compilers prefer using direct-initialization and copy
+          assignment of optional references to copy-initialization and assignment
+          from <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>:
+        </p>
+<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or1</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or2</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>  <span class="comment">// not portable</span>
+<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span>                       <span class="comment">// not portable</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or3</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>   <span class="comment">// portable</span>
+<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
+</pre>
+<p>
+          In order to check if your compiler correctly implements reference binding
+          use this test program.
+        </p>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cassert</span><span class="special">&gt;</span>
+
+<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">global_i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
+
+<span class="keyword">struct</span> <span class="identifier">TestingReferenceBinding</span>
+<span class="special">{</span>
+  <span class="identifier">TestingReferenceBinding</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">ii</span><span class="special">)</span>
+  <span class="special">{</span>
+    <span class="identifier">assert</span><span class="special">(&amp;</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&amp;</span><span class="identifier">global_i</span><span class="special">);</span>
+  <span class="special">}</span>
+
+  <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">ii</span><span class="special">)</span>
+  <span class="special">{</span>
+    <span class="identifier">assert</span><span class="special">(&amp;</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&amp;</span><span class="identifier">global_i</span><span class="special">);</span>
+  <span class="special">}</span>
+
+  <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">int</span><span class="special">&amp;&amp;)</span> <span class="comment">// remove this if your compiler doesn't have rvalue refs</span>
+  <span class="special">{</span>
+    <span class="identifier">assert</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
+  <span class="special">}</span>
+<span class="special">};</span>
+
+<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
+<span class="special">{</span>
+  <span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">iref</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+  <span class="identifier">assert</span><span class="special">(&amp;</span><span class="identifier">iref</span> <span class="special">==</span> <span class="special">&amp;</span><span class="identifier">global_i</span><span class="special">);</span>
+
+  <span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+  <span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+
+  <span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
+  <span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
+<span class="special">}</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html

@@ -49,7 +49,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html

@@ -46,7 +46,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/header__boost_optional_hpp_.html

@@ -6,7 +6,7 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/reference.html" title="Reference">
-<link rel="prev" href="header__boost_optional_optional_hpp_/detailed_semantics.html" title="Detailed Semantics">
+<link rel="prev" href="header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html" title="Detailed Semantics - Free Functions">
 <link rel="next" href="../dependencies_and_portability.html" title="Dependencies and Portability">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="header__boost_optional_optional_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -33,7 +33,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -41,7 +41,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="header__boost_optional_optional_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html

@@ -52,7 +52,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html

@@ -6,8 +6,8 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../../index.html" title="Boost.Optional">
 <link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
-<link rel="prev" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
-<link rel="next" href="../header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">
+<link rel="prev" href="header_optional_optional_refs.html" title="Optional References">
+<link rel="next" href="header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 <table cellpadding="2" width="100%"><tr>
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h4 class="title">
@@ -2368,10 +2368,48 @@
 </pre>
             </li>
 </ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">y</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+              refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+              to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+              refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+              referred to before the swap.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+              [endsect]
+            </li>
+</ul></div>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -2379,7 +2417,7 @@
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doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____free_functions.html

@@ -0,0 +1,447 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics -- Free Functions</title>
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+<a accesskey="p" href="detailed_semantics____optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics____free_functions"></a><a class="link" href="detailed_semantics____free_functions.html" title="Detailed Semantics -- Free Functions">Detailed
+        Semantics -- Free Functions</a>
+</h4></div></div></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span><span class="special">(</span>
+            <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+              type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional&lt;int&gt;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">&gt;</span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+            <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+              type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">calculate_foo</span><span class="special">()</span>
+<span class="special">{</span>
+  <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
+  <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
+<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
+  <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
+              and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
+              <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
+              <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
+              If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
+              If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+              that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+              not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> containing any value, and equal
+              to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> not containing a value. Pointers
+              have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+              has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect
+              to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
+              instead
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span>  <span class="comment">// Identity implies equality</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span>  <span class="comment">//</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span>  <span class="comment">// Initialized unequal to initialized.</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span>  <span class="comment">//</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&lt;</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special">&lt;</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result
+              shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">&lt;</span>
+              <span class="special">*</span><span class="identifier">y</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+              that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+              not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> containing any value, and equivalent
+              to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> not containing a value. Pointers
+              have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+              has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code> directly in generic code which
+              expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
+              instead. <code class="computeroutput"><span class="identifier">T</span></code> need not
+              be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only
+              single <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code>
+              is required. Other relational operations are defined in terms of this
+              one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code>
+              satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity,
+              antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>  <span class="comment">// Identity implies equivalence</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special">&lt;</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">o0</span> <span class="special">);</span>     <span class="comment">// Uninitialized is less than initialized</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">&lt;</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span>    <span class="comment">// Two initialized compare as (*lhs &lt; *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special">&lt;</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special">&lt;</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">x</span> <span class="special">==</span>
+              <span class="identifier">y</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&gt;</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
+              <span class="identifier">y</span> <span class="special">&lt;</span>
+              <span class="identifier">x</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&lt;=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">y</span> <span class="special">&lt;</span>
+              <span class="identifier">x</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&gt;=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">x</span> <span class="special">&lt;</span>
+              <span class="identifier">y</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">none_t</span><span class="special">,</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">none_t</span><span class="special">,</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">x</span> <span class="special">==</span>
+              <span class="identifier">y</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">y</span>
+            <span class="special">)</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+            </li>
+<li class="listitem">
+<p class="simpara">
+              <span class="bold"><strong>Effects:</strong></span>
+            </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+                    </td>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+                      </p>
+                    </td>
+</tr>
+<tr>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+                        contains a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
+                        an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+                        with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
+                        <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+                        contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
+                        does not contain a value
+                      </p>
+                    </td>
+</tr>
+<tr>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+                        does not contain a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
+                        as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression
+                        <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>,
+                        followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value
+                        and <code class="computeroutput"><span class="identifier">rhs</span></code> contains
+                        a value
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        no effect
+                      </p>
+                    </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
+              interchanged.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
+              <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;,</span><span class="identifier">T</span><span class="special">&amp;)</span></code>
+              throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="special">)</span></code>
+              throws.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">def0</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">def1</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">y</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+              refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+              to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+              refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+              referred to before the swap.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+              [endsect]
+            </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics____optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
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+<link rel="next" href="detailed_semantics____free_functions.html" title="Detailed Semantics -- Free Functions">
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+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics____optional_references"></a><a class="link" href="detailed_semantics____optional_references.html" title="Detailed Semantics -- Optional References">Detailed
+        Semantics -- Optional References</a>
+</h4></div></div></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_default_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&amp;&gt;::</span><span class="identifier">optional</span><span class="special">()</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&amp;&gt;::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">none_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> refers to nothing.
+            </li></ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics____optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics____free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

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+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics - Free Functions</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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+<link rel="next" href="../header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">
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+</tr></table>
+<hr>
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+<a accesskey="p" href="detailed_semantics___optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics___free_functions"></a><a class="link" href="detailed_semantics___free_functions.html" title="Detailed Semantics - Free Functions">Detailed
+        Semantics - Free Functions</a>
+</h4></div></div></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span><span class="special">(</span>
+            <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+              type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional&lt;int&gt;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span><span class="special">(</span>
+            <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;(</span><span class="identifier">condition</span><span class="special">,</span> <span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+              type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">calculate_foo</span><span class="special">()</span>
+<span class="special">{</span>
+  <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
+  <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
+<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
+  <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
+              and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
+              <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
+              <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
+              If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
+              If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+              that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+              not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> containing any value, and equal
+              to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> not containing a value. Pointers
+              have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+              has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect
+              to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
+              instead
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span>  <span class="comment">// Identity implies equality</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span>  <span class="comment">//</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span>  <span class="comment">// Initialized unequal to initialized.</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span>  <span class="comment">//</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&lt;</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special">&lt;</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result
+              shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">&lt;</span>
+              <span class="special">*</span><span class="identifier">y</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+              that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+              not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> containing any value, and equivalent
+              to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> not containing a value. Pointers
+              have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+              has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code> directly in generic code which
+              expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
+              instead. <code class="computeroutput"><span class="identifier">T</span></code> need not
+              be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only
+              single <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code>
+              is required. Other relational operations are defined in terms of this
+              one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;</span></code>
+              satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity,
+              antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>  <span class="comment">// Identity implies equivalence</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special">&lt;</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">&lt;</span> <span class="identifier">o0</span> <span class="special">);</span>     <span class="comment">// Uninitialized is less than initialized</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special">&lt;</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">&lt;</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span>    <span class="comment">// Two initialized compare as (*lhs &lt; *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special">&lt;</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special">&lt;</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">x</span> <span class="special">==</span>
+              <span class="identifier">y</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&gt;</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
+              <span class="identifier">y</span> <span class="special">&lt;</span>
+              <span class="identifier">x</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&lt;=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">y</span> <span class="special">&lt;</span>
+              <span class="identifier">x</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">&gt;=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+              <span class="identifier">x</span> <span class="special">&lt;</span>
+              <span class="identifier">y</span> <span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">==</span> <span class="special">(</span>
+            <span class="identifier">none_t</span><span class="special">,</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+            <span class="special">!=</span> <span class="special">(</span>
+            <span class="identifier">none_t</span><span class="special">,</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span></code>
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_free_get_pointer"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_pointer</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">o</span>
+            <span class="special">)</span> <span class="special">-&gt;</span>
+            <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">pointer_type</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_pointer</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">o</span> <span class="special">)</span> <span class="special">-&gt;</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">pointer_const_type</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">o</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> Nothing.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_free_get_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">o</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_type</span> <span class="identifier">def</span>
+            <span class="special">)</span> <span class="special">-&gt;</span>
+            <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_type</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">o</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_const_type</span> <span class="identifier">def</span>
+            <span class="special">)</span> <span class="special">-&gt;</span>
+            <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_const_type</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">o</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">def</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> Nothing.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> This function is deprecated.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">y</span>
+            <span class="special">)</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+            </li>
+<li class="listitem">
+<p class="simpara">
+              <span class="bold"><strong>Effects:</strong></span>
+            </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+                    </td>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+                      </p>
+                    </td>
+</tr>
+<tr>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+                        contains a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
+                        an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+                        with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
+                        <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+                        contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
+                        does not contain a value
+                      </p>
+                    </td>
+</tr>
+<tr>
+<td>
+                      <p>
+                        <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+                        does not contain a value</strong></span>
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
+                        as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression
+                        <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>,
+                        followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value
+                        and <code class="computeroutput"><span class="identifier">rhs</span></code> contains
+                        a value
+                      </p>
+                    </td>
+<td>
+                      <p>
+                        no effect
+                      </p>
+                    </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
+              interchanged.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
+              <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;,</span><span class="identifier">T</span><span class="special">&amp;)</span></code>
+              throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="special">)</span></code>
+              throws.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">def0</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">def1</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+            <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">y</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+              refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+              to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+              refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+              referred to before the swap.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+            </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics___optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html

@@ -0,0 +1,515 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics - Optional References</title>
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+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
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+<a accesskey="p" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics___optional_references"></a><a class="link" href="detailed_semantics___optional_references.html" title="Detailed Semantics - Optional References">Detailed
+        Semantics - Optional References</a>
+</h4></div></div></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_default_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span><span class="special">()</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">none_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">false</span></code>; <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> refers to nothing.
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_value_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>; <code class="computeroutput"><span class="identifier">addressof</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+              is an lvalue reference, the program is ill-formed. This constructor
+              does not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;</span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This constructor is declared
+              <code class="computeroutput"><span class="keyword">explicit</span></code> on compilers
+              that do not correctly suport binding to const lvalues of integral types.
+              For more details <a class="link" href="../../dependencies_and_portability/optional_reference_binding.html#optional_reference_binding">see here</a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_cond_value_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span><span class="special">(</span><span class="keyword">bool</span> <span class="identifier">cond</span><span class="special">,</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span>
+            <span class="identifier">r</span><span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">cond</span> <span class="special">?</span>
+              <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">nullptr</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">cond</span></code>; If <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>, <code class="computeroutput"><span class="identifier">addressof</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+              is an lvalue reference, the program is ill-formed. This constructor
+              does not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;</span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_copy_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span> <span class="special">(</span>
+            <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span>  <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_ctor_from_opt_U"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">optional</span> <span class="special">(</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;&gt;</span>
+            <span class="keyword">const</span><span class="special">&amp;</span>
+            <span class="identifier">rhs</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_convertible</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;,</span> <span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value</span></code>
+              is <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_assign_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+              with expression <code class="computeroutput"><span class="keyword">nullptr</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">false</span></code>.
+            </li>
+</ul></div>
+<a name="reference_optional_ref_copy_assign"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&amp;</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
+            <span class="keyword">const</span><span class="special">&amp;</span>
+            <span class="identifier">rhs</span> <span class="special">)</span>
+            <span class="keyword">noexcept</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+              with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This behaviour is called <span class="emphasis"><em>rebinding
+              semantics</em></span>. See <a class="link" href="../../tutorial/optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+              for details.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<a name="reference_optional_ref_assign_optional_U"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_convertible</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;,</span> <span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value</span></code>
+              is <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+              with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_assign_R"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+              with expression <code class="computeroutput"><span class="identifier">r</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+              is an lvalue reference, the program is ill-formed. This function does
+              not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;</span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_emplace_R"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span>
+            <span class="special">)</span> <span class="keyword">noexcept</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+              with expression <code class="computeroutput"><span class="identifier">r</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+              is an lvalue reference, the program is ill-formed. This function does
+              not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;</span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span> <span class="special">*()</span>
+            <span class="keyword">const</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Returns <code class="computeroutput"><span class="special">*</span><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws: </strong></span> Nothing.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span> <span class="special">-&gt;</span>
+            <span class="special">()</span> <span class="keyword">const</span>
+            <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects: </strong></span> Returns <code class="computeroutput"><span class="identifier">ref</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws: </strong></span> Nothing.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span>
+            <span class="special">)</span> <span class="keyword">const</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+              <span class="identifier">r</span><span class="special">;</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+              is an lvalue reference, the program is ill-formed.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_value_or_eval"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+              <span class="identifier">f</span><span class="special">();</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">())</span></code> is an lvalue reference, the program
+              is ill-formed.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+            <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">get_ptr</span> <span class="special">()</span>
+            <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">ref</span></code>.
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span> <span class="keyword">bool</span>
+            <span class="special">()</span> <span class="keyword">const</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">ref</span><span class="special">)</span></code>.
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="keyword">operator</span> <span class="special">!</span> <span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+              <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="keyword">bool</span><span class="special">(</span><span class="identifier">ref</span><span class="special">)</span></code>.
+            </li></ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Use <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code> instead.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span>
+            <span class="identifier">r</span><span class="special">)</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;(</span><span class="identifier">r</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span>
+            <span class="special">)</span> <span class="keyword">const</span>
+            <span class="keyword">noexcept</span><span class="special">;</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">value_or</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;(</span><span class="identifier">r</span><span class="special">);</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+            </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html

@@ -0,0 +1,47 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header &lt;boost/optional.hpp&gt;</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="prev" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="next" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header__boost_optional_hpp_"></a><a class="link" href="header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">Header
+        &lt;boost/optional.hpp&gt;</a>
+</h4></div></div></div>
+<p>
+          This is an alias for header <a class="link" href="../../../optional/reference/header__boost_optional_optional_hpp_.html#boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional" title="Synopsis"><code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code></a>.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html

@@ -0,0 +1,114 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional References</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="prev" href="header_optional_optional_values.html" title="Optional Values">
+<link rel="next" href="detailed_semantics___optional_values.html" title="Detailed Semantics - Optional Values">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional_refs"></a><a class="link" href="header_optional_optional_refs.html" title="Optional References">Optional
+        References</a>
+</h4></div></div></div>
+<a name="reference_operator_template_spec"></a><pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
+<span class="keyword">class</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="comment">// specilization for lvalue references</span>
+<span class="special">{</span>
+<span class="keyword">public</span> <span class="special">:</span>
+
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">value_type</span><span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">reference_type</span><span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">reference_const_type</span><span class="special">;</span> <span class="comment">// no const propagation</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">rval_reference_type</span><span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">pointer_type</span><span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">pointer_const_type</span><span class="special">;</span>   <span class="comment">// no const propagation</span>
+
+    <span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_default_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_default_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span>  <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="keyword">bool</span> <span class="identifier">cond</span><span class="special">,</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_cond_value_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_copy_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_ctor_from_opt_U"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_copy_assign"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&amp;&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_optional_U"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span><span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_R"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&amp;&amp;</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_emplace_R"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">-&gt;()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">R</span> <span class="special">&amp;&amp;</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_or"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_or_eval"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_operator_not"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// deprecated methods</span>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_reset"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">R</span> <span class="special">&amp;&amp;</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_reset_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_is_initialized"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">&gt;</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">R</span> <span class="special">&amp;&amp;</span> <span class="identifier">r</span> <span class="special">)</span> <span class="identifier">constnoexcept</span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get_value_or_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+<span class="keyword">private</span><span class="special">:</span>
+    <span class="identifier">T</span><span class="special">*</span> <span class="identifier">ref</span><span class="special">;</span> <span class="comment">// exposition only</span>
+<span class="special">};</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html

@@ -0,0 +1,141 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional Values</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
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+<link rel="next" href="header_optional_optional_refs.html" title="Optional References">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional_values"></a><a class="link" href="header_optional_optional_values.html" title="Optional Values">Optional
+        Values</a>
+</h4></div></div></div>
+<a name="reference_operator_template"></a><pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
+<span class="keyword">class</span> <span class="identifier">optional</span>
+<span class="special">{</span>
+<span class="keyword">public</span> <span class="special">:</span>
+
+    <span class="keyword">typedef</span> <span class="identifier">T</span>         <span class="identifier">value_type</span> <span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">&amp;</span>       <span class="identifier">reference_type</span> <span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span>  <span class="identifier">reference_const_type</span> <span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">&amp;&amp;</span>      <span class="identifier">rval_reference_type</span> <span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">*</span>       <span class="identifier">pointer_type</span> <span class="special">;</span>
+    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span>  <span class="identifier">pointer_const_type</span> <span class="special">;</span>
+
+    <span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_move_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// [new in 1.34]</span>
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_bool_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_move_constructor_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_move_constructor_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_emplace"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="identifier">get</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">-&gt;()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">*</span>       <span class="keyword">operator</span> <span class="special">-&gt;()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;&amp;</span>      <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="identifier">value</span><span class="special">()</span> <span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">&amp;&amp;</span>      <span class="identifier">value</span><span class="special">()</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_call"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_call_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="identifier">T</span><span class="special">*</span>       <span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// deprecated methods</span>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_reset"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_reset_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_is_initialized"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="comment">// (deprecated)</span>
+    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="keyword">default</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+<span class="special">};</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/io_header.html

@@ -58,7 +58,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/io_header/io_semantics.html

@@ -98,7 +98,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/reference/relnotes.html

@@ -0,0 +1,183 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Release Notes</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
+<link rel="next" href="acknowledgements.html" title="Acknowledgements">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.relnotes"></a><a class="link" href="relnotes.html" title="Release Notes">Release Notes</a>
+</h3></div></div></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h0"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_x_xx"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_x_xx">Boost Release
+        X.XX</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+            Now <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code> is specialized for reference
+            parameters. This way the <code class="computeroutput"><span class="keyword">sizeof</span></code>
+            of optional reference is that of a pointer, and a number of bugs is avoided.
+          </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h1"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_60"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_60">Boost Release
+        1.60</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+            Changed the implementation of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+            again. Now it is a const object with internal linkage (as any other tag).
+            This fixes <a href="https://svn.boost.org/trac/boost/ticket/11203" target="_top">Trac
+            #11203</a>.
+          </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h2"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_59"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_59">Boost Release
+        1.59</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+            For C++03 compilers, added 0-argument overload for member function <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code>,
+            and therewith removed the dependency on <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">utility</span><span class="special">/</span><span class="identifier">in_place_factory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>.
+          </li>
+<li class="listitem">
+            Fixed <a href="https://svn.boost.org/trac/boost/ticket/11241" target="_top">Trac
+            #11241</a>.
+          </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h3"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_58"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_58">Boost Release
+        1.58</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+            <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> is no longer convertible from
+            literal <code class="computeroutput"><span class="number">0</span></code>. This avoids a
+            bug where <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">rational</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;&gt;</span>
+            <span class="identifier">oi</span> <span class="special">=</span>
+            <span class="number">0</span><span class="special">;</span></code>
+            would initialize an optional object with no contained value.
+          </li>
+<li class="listitem">
+            Improved the trick that prevents streaming out <code class="computeroutput"><span class="identifier">optional</span></code>
+            without header <code class="computeroutput"><span class="identifier">optional_io</span><span class="special">.</span><span class="identifier">hpp</span></code>
+            by using safe-bool idiom. This addresses <a href="https://svn.boost.org/trac/boost/ticket/10825" target="_top">Trac
+            #10825</a>.
+          </li>
+<li class="listitem">
+            IOStream operators are now mentioned in documentation.
+          </li>
+<li class="listitem">
+            Added a way to manually disable move semantics: just define macro <code class="computeroutput"><span class="identifier">BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES</span></code>.
+            This can be used to work around <a href="https://svn.boost.org/trac/boost/ticket/10399" target="_top">Trac
+            #10399</a>.
+          </li>
+<li class="listitem">
+            It is no longer possible to assign <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code> to <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> when <code class="computeroutput"><span class="identifier">U</span></code>
+            is not assignable or convertible to <code class="computeroutput"><span class="identifier">T</span></code>
+            (<a href="https://svn.boost.org/trac/boost/ticket/11087" target="_top">Trac #11087</a>).
+          </li>
+<li class="listitem">
+            Value accessors now work correctly on rvalues of <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> (<a href="https://svn.boost.org/trac/boost/ticket/10839" target="_top">Trac
+            #10839</a>).
+          </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h4"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_57"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_57">Boost Release
+        1.57</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+            <a href="https://github.com/boostorg/optional/pull/9" target="_top">Git pull #9</a>:
+            <span class="emphasis"><em>"Supply <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span></code>
+            to fix C++03 compile error on <code class="computeroutput"><span class="identifier">logic_error</span><span class="special">(</span><span class="string">"..."</span><span class="special">)</span></code>"</em></span>.
+          </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h5"></a>
+        <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_56"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_56">Boost Release
+        1.56</a>
+      </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+            Added support for rvalue references. Now <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> works with moveable but non-copyable
+            <code class="computeroutput"><span class="identifier">T</span></code>'s,
+          </li>
+<li class="listitem">
+            Improved <code class="computeroutput"><span class="identifier">swap</span></code> (now uses
+            move operations),
+          </li>
+<li class="listitem">
+            Added function <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code>. This is the last of the requests from
+            <a href="https://svn.boost.org/trac/boost/ticket/1841" target="_top">Trac #1841</a>,
+          </li>
+<li class="listitem">
+            <code class="computeroutput"><span class="identifier">optional</span></code> is moveable,
+            including conditional <code class="computeroutput"><span class="keyword">noexcept</span></code>
+            specifications, which make it <code class="computeroutput"><span class="identifier">move_if_noexcept</span></code>-friendly,
+          </li>
+<li class="listitem">
+            Using explicit operator bool() on platforms that support it (<a href="https://svn.boost.org/trac/boost/ticket/4227" target="_top">Trac
+            #4227</a>) (breaking change),
+          </li>
+<li class="listitem">
+            Forward declaration of <code class="computeroutput"><span class="keyword">operator</span><span class="special">&lt;&lt;(</span><span class="identifier">ostream</span><span class="special">&amp;,</span> <span class="identifier">optional</span>
+            <span class="keyword">const</span><span class="special">&amp;)</span></code>
+            to prevent inadvertent incorrect serialization of optional objects,
+          </li>
+<li class="listitem">
+            Removed deprecated function <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> from examples (<a href="https://svn.boost.org/trac/boost/ticket/9005" target="_top">Trac
+            #9005</a>),
+          </li>
+<li class="listitem">
+            Equality comparison with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+            does not require that <code class="computeroutput"><span class="identifier">T</span></code>
+            be EqualityComparable,
+          </li>
+<li class="listitem">
+            Optional rvalue references are explicitly disallowed,
+          </li>
+<li class="listitem">
+            Binding temporaries to optional references is explicitly disallowed (breaking
+            change),
+          </li>
+<li class="listitem">
+            More ways to access the contained value, functions <code class="computeroutput"><span class="identifier">value</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">value_or_eval</span><span class="special">()</span></code>,
+          </li>
+<li class="listitem">
+            Updated and reorganized documentation, added tutorial and quick guide
+            sections.
+          </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/relnotes.html

@@ -28,6 +28,57 @@
 </h2></div></div></div>
 <h4>
 <a name="boost_optional.relnotes.h0"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_62"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_62">Boost
+      Release 1.62</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+          Fixed <a href="https://svn.boost.org/trac/boost/ticket/12179" target="_top">Trac #12179</a>.
+        </li></ul></div>
+<h4>
+<a name="boost_optional.relnotes.h1"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_61"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_61">Boost
+      Release 1.61</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+          Now <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code> is specialized for reference
+          parameters. This addresses a couple of issues:
+          <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
+<li class="listitem">
+                the <code class="computeroutput"><span class="keyword">sizeof</span></code> of optional
+                reference is that of a pointer,
+              </li>
+<li class="listitem">
+                some bugs connected to copying optional references are gone,
+              </li>
+<li class="listitem">
+                all run-time bugs caused by incorrect reference binding on some compilers
+                are now turned into compile-time errors,
+              </li>
+<li class="listitem">
+                you can swap optional references: it is like swapping pointers: shalow,
+                underlying objects are not affected,
+              </li>
+<li class="listitem">
+                optional references to abstract types work.
+              </li>
+</ul></div>
+        </li>
+<li class="listitem">
+          Documented nested typedefs (<a href="https://svn.boost.org/trac/boost/ticket/5193" target="_top">Trac
+          #5193</a>).
+        </li>
+<li class="listitem">
+          Made the perfect-forwarding constructor SFINAE-friendly, which fixes <a href="https://svn.boost.org/trac/boost/ticket/12002" target="_top">Trac #12002</a>.
+          However, this only works in the newer platforms that correctly implement
+          C++11 <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">type_traits</span><span class="special">&gt;</span></code>.
+        </li>
+<li class="listitem">
+          Fixed <a href="https://svn.boost.org/trac/boost/ticket/10445" target="_top">Trac #10445</a>.
+        </li>
+</ul></div>
+<h4>
+<a name="boost_optional.relnotes.h2"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_60"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_60">Boost
       Release 1.60</a>
     </h4>
@@ -38,7 +89,7 @@
           #11203</a>.
         </li></ul></div>
 <h4>
-<a name="boost_optional.relnotes.h1"></a>
+<a name="boost_optional.relnotes.h3"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_59"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_59">Boost
       Release 1.59</a>
     </h4>
@@ -52,7 +103,7 @@
         </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h2"></a>
+<a name="boost_optional.relnotes.h4"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_58"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_58">Boost
       Release 1.58</a>
     </h4>
@@ -88,7 +139,7 @@
         </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h3"></a>
+<a name="boost_optional.relnotes.h5"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_57"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_57">Boost
       Release 1.57</a>
     </h4>
@@ -98,7 +149,7 @@
           to fix C++03 compile error on <code class="computeroutput"><span class="identifier">logic_error</span><span class="special">(</span><span class="string">"..."</span><span class="special">)</span></code>"</em></span>.
         </li></ul></div>
 <h4>
-<a name="boost_optional.relnotes.h4"></a>
+<a name="boost_optional.relnotes.h6"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_56"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_56">Boost
       Release 1.56</a>
     </h4>
@@ -155,7 +206,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/a_note_about_optional_bool_.html

@@ -94,7 +94,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/design_overview.html

@@ -170,7 +170,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/design_overview/the_interface.html

@@ -142,10 +142,10 @@
           about the possibly uninitialized state appealing to the familiar pointer
           semantics w.r.t. to null pointers.
         </p>
-<div class="warning"><table border="0" summary="Warning">
+<div class="caution"><table border="0" summary="Caution">
 <tr>
-<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../../doc/src/images/warning.png"></td>
-<th align="left">Warning</th>
+<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../../doc/src/images/caution.png"></td>
+<th align="left">Caution</th>
 </tr>
 <tr><td align="left" valign="top"><p>
             However, it is particularly important to note that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code> objects are not pointers. <span class="underline"><code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code> is not, and does not model, a
@@ -173,7 +173,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/design_overview/the_semantics.html

@@ -107,7 +107,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/exception_safety_guarantees.html

@@ -6,7 +6,7 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
-<link rel="prev" href="a_note_about_optional_bool_.html" title="A note about optional&lt;bool&gt;">
+<link rel="prev" href="gotchas/false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">
 <link rel="next" href="type_requirements.html" title="Type requirements">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
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+<a accesskey="p" href="gotchas/false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -161,7 +161,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -169,7 +169,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="a_note_about_optional_bool_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="gotchas/false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/tutorial/gotchas.html

@@ -0,0 +1,112 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Gotchas</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/tutorial.html" title="Tutorial">
+<link rel="prev" href="in_place_factories.html" title="In-Place Factories">
+<link rel="next" href="gotchas/moved_from__optional_.html" title="Moved-from optional">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="in_place_factories.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas/moved_from__optional_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.tutorial.gotchas"></a><a class="link" href="gotchas.html" title="Gotchas">Gotchas</a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.a_note_about_optional_bool_"></a><a class="link" href="gotchas.html#boost_optional.tutorial.gotchas.a_note_about_optional_bool_" title="A note about optional&lt;bool&gt;">A
+        note about optional&lt;bool&gt;</a>
+</h4></div></div></div>
+<p>
+          <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>
+          should be used with special caution and consideration.
+        </p>
+<p>
+          First, it is functionally similar to a tristate boolean (false, maybe,
+          true) &#8212;such as <a href="../../../../../../doc/html/tribool.html" target="_top">boost::tribool</a>&#8212;
+          except that in a tristate boolean, the maybe state <span class="underline">represents
+          a valid value</span>, unlike the corresponding state of an uninitialized
+          <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>.
+          It should be carefully considered if an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code> instead of a <code class="computeroutput"><span class="identifier">tribool</span></code>
+          is really needed.
+        </p>
+<p>
+          Second, although <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code> provides a contextual conversion
+          to <code class="computeroutput"><span class="keyword">bool</span></code> in C++11, this falls
+          back to an implicit conversion on older compilers. This conversion refers
+          to the initialization state and not to the contained value. Using <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>
+          can lead to subtle errors due to the implicit <code class="computeroutput"><span class="keyword">bool</span></code>
+          conversion:
+        </p>
+<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">void</span> <span class="identifier">bar</span><span class="special">()</span>
+<span class="special">{</span>
+    <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="keyword">try</span><span class="special">();</span>
+
+    <span class="comment">// The following intended to pass the value of 'v' to foo():</span>
+    <span class="identifier">foo</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+    <span class="comment">// But instead, the initialization state is passed</span>
+    <span class="comment">// due to a typo: it should have been foo(*v).</span>
+<span class="special">}</span>
+</pre>
+<p>
+          The only implicit conversion is to <code class="computeroutput"><span class="keyword">bool</span></code>,
+          and it is safe in the sense that typical integral promotions don't apply
+          (i.e. if <code class="computeroutput"><span class="identifier">foo</span><span class="special">()</span></code>
+          takes an <code class="computeroutput"><span class="keyword">int</span></code> instead, it won't
+          compile).
+        </p>
+<p>
+          Third, mixed comparisons with <code class="computeroutput"><span class="keyword">bool</span></code>
+          work differently than similar mixed comparisons between pointers and <code class="computeroutput"><span class="keyword">bool</span></code>, so the results might surprise you:
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span> <span class="identifier">oEmpty</span><span class="special">(</span><span class="identifier">none</span><span class="special">),</span> <span class="identifier">oTrue</span><span class="special">(</span><span class="keyword">true</span><span class="special">),</span> <span class="identifier">oFalse</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>  <span class="comment">// renders true</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders false!</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>  <span class="comment">// renders false!</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>  <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders true!</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>  <span class="comment">// renders false</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>   <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span>  <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>   <span class="comment">// renders true</span>
+</pre>
+<p>
+          In other words, for <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code>, the following assertion does not
+          hold:
+        </p>
+<pre class="programlisting"><span class="identifier">assert</span><span class="special">((</span><span class="identifier">opt</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">)</span> <span class="special">==</span> <span class="special">(!</span><span class="identifier">opt</span><span class="special">));</span>
+</pre>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="in_place_factories.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas/moved_from__optional_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/false_positive_with__wmaybe_uninitialized.html

@@ -0,0 +1,77 @@
+<html>
+<head>
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+<title>False positive with -Wmaybe-uninitialized</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../exception_safety_guarantees.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.false_positive_with__wmaybe_uninitialized"></a><a class="link" href="false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">False
+        positive with -Wmaybe-uninitialized</a>
+</h4></div></div></div>
+<p>
+          Sometimes on GCC compilers below version 5.1 you may get an -Wmaybe-uninitialized
+          warning when copiling with option -02 on a perfectly valid <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code> usage. For instance in this
+          program:
+        </p>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">getitem</span><span class="special">();</span>
+
+<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*[])</span>
+<span class="special">{</span>
+  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">a</span> <span class="special">=</span> <span class="identifier">getitem</span><span class="special">();</span>
+  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">b</span><span class="special">;</span>
+
+  <span class="keyword">if</span> <span class="special">(</span><span class="identifier">argc</span> <span class="special">&gt;</span> <span class="number">0</span><span class="special">)</span>
+    <span class="identifier">b</span> <span class="special">=</span> <span class="identifier">argc</span><span class="special">;</span>
+
+  <span class="keyword">if</span> <span class="special">(</span><span class="identifier">a</span> <span class="special">!=</span> <span class="identifier">b</span><span class="special">)</span>
+    <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
+
+  <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
+<span class="special">}</span>
+</pre>
+<p>
+          This is a bug in the compiler. As a workaround (provided in <a href="http://stackoverflow.com/questions/21755206/how-to-get-around-gcc-void-b-4-may-be-used-uninitialized-in-this-funct" target="_top">this
+          Stack Overflow question</a>) use the following way of initializing
+          an optional containing no value:
+        </p>
+<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">b</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">make_optional</span><span class="special">(</span><span class="keyword">false</span><span class="special">,</span> <span class="keyword">int</span><span class="special">());</span>
+</pre>
+<p>
+          This is obviously redundant, but makes the warning disappear.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../exception_safety_guarantees.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/mixed_relational_comparisons.html

@@ -0,0 +1,59 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Mixed relational comparisons</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../gotchas.html" title="Gotchas">
+<link rel="prev" href="moved_from__optional_.html" title="Moved-from optional">
+<link rel="next" href="false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">
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+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
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+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="moved_from__optional_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.mixed_relational_comparisons"></a><a class="link" href="mixed_relational_comparisons.html" title="Mixed relational comparisons">Mixed
+        relational comparisons</a>
+</h4></div></div></div>
+<p>
+          Because <code class="computeroutput"><span class="identifier">T</span></code> is convertible
+          to <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          and because <code class="computeroutput"><span class="identifier">opiotnal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> when <code class="computeroutput"><span class="identifier">T</span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>, you can sometimes
+          get an unexpected runtime result where you would rather expect a compiler
+          error:
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">Flight_plan</span><span class="special">::</span><span class="identifier">weight</span><span class="special">();</span> <span class="comment">// sometimes no weight can be returned</span>
+
+<span class="keyword">bool</span> <span class="identifier">is_aircraft_too_heavy</span><span class="special">(</span><span class="identifier">Flight_plan</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">p</span><span class="special">)</span>
+<span class="special">{</span>
+   <span class="keyword">return</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">weight</span><span class="special">()</span> <span class="special">&gt;</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">aircraft</span><span class="special">().</span><span class="identifier">max_weight</span><span class="special">();</span> <span class="comment">// compiles!</span>
+<span class="special">}</span>                                                 <span class="comment">// returns false when the optional contains no value </span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="moved_from__optional_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/moved_from__optional_.html

@@ -0,0 +1,63 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Moved-from optional</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../gotchas.html" title="Gotchas">
+<link rel="prev" href="../gotchas.html" title="Gotchas">
+<link rel="next" href="mixed_relational_comparisons.html" title="Mixed relational comparisons">
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+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../gotchas.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.moved_from__optional_"></a><a class="link" href="moved_from__optional_.html" title="Moved-from optional">Moved-from
+        <code class="computeroutput"><span class="identifier">optional</span></code></a>
+</h4></div></div></div>
+<p>
+          When an optional object that contains a value is moved from (is a source
+          of move constructor or assignment) it still contains a value and its contained
+          value is left in a moved-from state. This can be illustrated with the following
+          example.
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;&gt;</span> <span class="identifier">opi</span> <span class="special">{</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">make_unique</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="number">1</span><span class="special">)};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;&gt;</span> <span class="identifier">opj</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opi</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">opi</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opi</span> <span class="special">==</span> <span class="keyword">nullptr</span><span class="special">);</span>
+</pre>
+<p>
+          Quite a lot of people expect that when an object that contains a value
+          is moved from, its contained value should be destroyed. This is not so,
+          for performance reasons. Current semantics allow the implementation of
+          <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">opiotnal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          to be trivially copyable when <code class="computeroutput"><span class="identifier">T</span></code>
+          is trivial.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../gotchas.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/in_place_factories.html

@@ -6,8 +6,8 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
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-<link rel="next" href="a_note_about_optional_bool_.html" title="A note about optional&lt;bool&gt;">
+<link rel="prev" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">
+<link rel="next" href="gotchas.html" title="Gotchas">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
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@@ -183,7 +183,7 @@
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 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -191,7 +191,7 @@
 </tr></table>
 <hr>
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+<a accesskey="p" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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doc/html/boost_optional/tutorial/io_operators.html

@@ -73,7 +73,7 @@
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 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/optional_references.html

@@ -7,7 +7,7 @@
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="io_operators.html" title="IO operators">
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+<link rel="next" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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@@ -20,88 +20,90 @@
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 <hr>
 <div class="spirit-nav">
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 <a name="boost_optional.tutorial.optional_references"></a><a class="link" href="optional_references.html" title="Optional references">Optional
       references</a>
 </h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.optional_references.overview"></a><a class="link" href="optional_references.html#boost_optional.tutorial.optional_references.overview" title="Overview">Overview</a>
+</h4></div></div></div>
 <p>
-        This library allows the template parameter <code class="computeroutput"><span class="identifier">T</span></code>
-        to be of reference type: <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>, and to some extent, <code class="computeroutput"><span class="identifier">T</span>
-        <span class="keyword">const</span><span class="special">&amp;</span></code>.
-      </p>
+          This library allows the template parameter <code class="computeroutput"><span class="identifier">T</span></code>
+          to be of reference type: <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>, and to some extent, <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span></code>.
+        </p>
 <p>
-        However, since references are not real objects some restrictions apply and
-        some operations are not available in this case:
-      </p>
+          However, since references are not real objects some restrictions apply
+          and some operations are not available in this case:
+        </p>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 <li class="listitem">
-            Converting constructors
-          </li>
+              Converting constructors
+            </li>
 <li class="listitem">
-            Converting assignment
-          </li>
+              Converting assignment
+            </li>
 <li class="listitem">
-            InPlace construction
-          </li>
+              InPlace construction
+            </li>
 <li class="listitem">
-            InPlace assignment
-          </li>
+              InPlace assignment
+            </li>
 <li class="listitem">
-            Value-access via pointer
-          </li>
+              Value-access via pointer
+            </li>
 </ul></div>
 <p>
-        Also, even though <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code>
-        treats it wrapped pseudo-object much as a real value, a true real reference
-        is stored so aliasing will ocurr:
-      </p>
+          Also, even though <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> treats it wrapped pseudo-object
+          much as a real value, a true real reference is stored so aliasing will
+          ocurr:
+        </p>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 <li class="listitem">
-            Copies of <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code>
-            will copy the references but all these references will nonetheless refer
-            to the same object.
-          </li>
+              Copies of <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> will copy the references but
+              all these references will nonetheless refer to the same object.
+            </li>
 <li class="listitem">
-            Value-access will actually provide access to the referenced object rather
-            than the reference itself.
-          </li>
+              Value-access will actually provide access to the referenced object
+              rather than the reference itself.
+            </li>
 </ul></div>
-<div class="warning"><table border="0" summary="Warning">
+<div class="caution"><table border="0" summary="Caution">
 <tr>
-<td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../doc/src/images/warning.png"></td>
-<th align="left">Warning</th>
+<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../doc/src/images/caution.png"></td>
+<th align="left">Caution</th>
 </tr>
 <tr><td align="left" valign="top"><p>
-          On compilers that do not conform to Standard C++ rules of reference binding,
-          operations on optional references might give adverse results: rather than
-          binding a reference to a designated object they may create an unexpected
-          temporary and bind to it. For more details see <a class="link" href="../dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">Dependencies
-          and Portability section</a>.
-        </p></td></tr>
+            On compilers that do not conform to Standard C++ rules of reference binding,
+            some operations on optional references are disabled in order to prevent
+            subtle bugs. For more details see <a class="link" href="../dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">Dependencies
+            and Portability section</a>.
+          </p></td></tr>
 </table></div>
-<h5>
-<a name="boost_optional.tutorial.optional_references.h0"></a>
-        <span class="phrase"><a name="boost_optional.tutorial.optional_references.rvalue_references"></a></span><a class="link" href="optional_references.html#boost_optional.tutorial.optional_references.rvalue_references">Rvalue
-        references</a>
-      </h5>
+<h6>
+<a name="boost_optional.tutorial.optional_references.overview.h0"></a>
+          <span class="phrase"><a name="boost_optional.tutorial.optional_references.overview.rvalue_references"></a></span><a class="link" href="optional_references.html#boost_optional.tutorial.optional_references.overview.rvalue_references">Rvalue
+          references</a>
+        </h6>
 <p>
-        Rvalue references and lvalue references to const have the ability in C++
-        to extend the life time of a temporary they bind to. Optional references
-        do not have this capability, therefore to avoid surprising effects it is
-        not possible to initialize an optional references from a temporary. Optional
-        rvalue references are disabled altogether. Also, the initialization and assignment
-        of an optional reference to const from rvalue reference is disabled.
-      </p>
+          Rvalue references and lvalue references to const have the ability in C++
+          to extend the life time of a temporary they bind to. Optional references
+          do not have this capability, therefore to avoid surprising effects it is
+          not possible to initialize an optional references from a temporary. Optional
+          rvalue references are disabled altogether. Also, the initialization and
+          assignment of an optional reference to const from rvalue reference is disabled.
+        </p>
 <pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>            <span class="comment">// legal</span>
 <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">oi</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> <span class="comment">// illegal</span>
 </pre>
 </div>
+</div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -109,7 +111,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="io_operators.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="io_operators.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/tutorial/optional_references/rebinding_semantics_for_assignment_of_optional_references.html

@@ -0,0 +1,147 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Rebinding semantics for assignment of optional references</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../optional_references.html" title="Optional references">
+<link rel="prev" href="../optional_references.html" title="Optional references">
+<link rel="next" href="../in_place_factories.html" title="In-Place Factories">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
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+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../optional_references.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../in_place_factories.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.optional_references.rebinding_semantics_for_assignment_of_optional_references"></a><a class="link" href="rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">Rebinding
+        semantics for assignment of optional references</a>
+</h4></div></div></div>
+<p>
+          If you assign to an <span class="emphasis"><em>uninitialized </em></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> the effect is to bind (for the
+          first time) to the object. Clearly, there is no other choice.
+        </p>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rx</span> <span class="special">=</span> <span class="identifier">x</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">ora</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// now 'ora' is bound to 'x' through 'rx'</span>
+<span class="special">*</span><span class="identifier">ora</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="comment">// Changes value of 'x' through 'ora'</span>
+<span class="identifier">assert</span><span class="special">(</span><span class="identifier">x</span><span class="special">==</span><span class="number">2</span><span class="special">);</span>
+</pre>
+<p>
+          If you assign to a bare C++ reference, the assignment is forwarded to the
+          referenced object; its value changes but the reference is never rebound.
+        </p>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// Changes the value of 'a' to 'b'</span>
+<span class="identifier">assert</span><span class="special">(</span><span class="identifier">a</span><span class="special">==</span><span class="identifier">b</span><span class="special">);</span>
+<span class="identifier">b</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span><span class="identifier">ra</span><span class="special">!=</span><span class="identifier">b</span><span class="special">);</span> <span class="comment">// 'ra' is not rebound to 'b'</span>
+</pre>
+<p>
+          Now, if you assign to an <span class="emphasis"><em>initialized </em></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code>,
+          the effect is to <span class="bold"><strong>rebind</strong></span> to the new object
+          instead of assigning the referee. This is unlike bare C++ references.
+        </p>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// 'ora' is rebound to 'b'</span>
+<span class="special">*</span><span class="identifier">ora</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span> <span class="comment">// Changes value of 'b' (not 'a')</span>
+<span class="identifier">assert</span><span class="special">(</span><span class="identifier">a</span><span class="special">==</span><span class="number">1</span><span class="special">);</span>
+<span class="identifier">assert</span><span class="special">(</span><span class="identifier">b</span><span class="special">==</span><span class="number">3</span><span class="special">);</span>
+</pre>
+<h6>
+<a name="boost_optional.tutorial.optional_references.rebinding_semantics_for_assignment_of_optional_references.h0"></a>
+          <span class="phrase"><a name="boost_optional.tutorial.optional_references.rebinding_semantics_for_assignment_of_optional_references.rationale"></a></span><a class="link" href="rebinding_semantics_for_assignment_of_optional_references.html#boost_optional.tutorial.optional_references.rebinding_semantics_for_assignment_of_optional_references.rationale">Rationale</a>
+        </h6>
+<p>
+          Rebinding semantics for the assignment of <span class="emphasis"><em>initialized </em></span>
+          <code class="computeroutput"><span class="identifier">optional</span></code> references has
+          been chosen to provide <span class="bold"><strong>consistency among initialization
+          states</strong></span> even at the expense of lack of consistency with the semantics
+          of bare C++ references. It is true that <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code> strives to behave as much as possible
+          as <code class="computeroutput"><span class="identifier">U</span></code> does whenever it is
+          initialized; but in the case when <code class="computeroutput"><span class="identifier">U</span></code>
+          is <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>,
+          doing so would result in inconsistent behavior w.r.t to the lvalue initialization
+          state.
+        </p>
+<p>
+          Imagine <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code>
+          forwarding assignment to the referenced object (thus changing the referenced
+          object value but not rebinding), and consider the following code:
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">a</span> <span class="special">=</span> <span class="identifier">get</span><span class="special">();</span>
+<span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span><span class="special">&amp;</span> <span class="identifier">rx</span> <span class="special">=</span> <span class="identifier">x</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">b</span><span class="special">(</span><span class="identifier">rx</span><span class="special">);</span>
+<span class="identifier">a</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+</pre>
+<p>
+          What does the assignment do?
+        </p>
+<p>
+          If <code class="computeroutput"><span class="identifier">a</span></code> is <span class="emphasis"><em>uninitialized</em></span>,
+          the answer is clear: it binds to <code class="computeroutput"><span class="identifier">x</span></code>
+          (we now have another reference to <code class="computeroutput"><span class="identifier">x</span></code>).
+          But what if <code class="computeroutput"><span class="identifier">a</span></code> is already
+          <span class="emphasis"><em>initialized</em></span>? it would change the value of the referenced
+          object (whatever that is); which is inconsistent with the other possible
+          case.
+        </p>
+<p>
+          If <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code>
+          would assign just like <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code> does, you would never be able to use
+          Optional's assignment without explicitly handling the previous initialization
+          state unless your code is capable of functioning whether after the assignment,
+          <code class="computeroutput"><span class="identifier">a</span></code> aliases the same object
+          as <code class="computeroutput"><span class="identifier">b</span></code> or not.
+        </p>
+<p>
+          That is, you would have to discriminate in order to be consistent.
+        </p>
+<p>
+          If in your code rebinding to another object is not an option, then it is
+          very likely that binding for the first time isn't either. In such case,
+          assignment to an <span class="emphasis"><em>uninitialized </em></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> shall be prohibited. It is quite
+          possible that in such a scenario it is a precondition that the lvalue must
+          be already initialized. If it isn't, then binding for the first time is
+          OK while rebinding is not which is IMO very unlikely. In such a scenario,
+          you can assign the value itself directly, as in:
+        </p>
+<pre class="programlisting"><span class="identifier">assert</span><span class="special">(!!</span><span class="identifier">opt</span><span class="special">);</span>
+<span class="special">*</span><span class="identifier">opt</span><span class="special">=</span><span class="identifier">value</span><span class="special">;</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../optional_references.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../in_place_factories.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/performance_considerations.html

@@ -67,7 +67,7 @@
         for your application (e.g., because you want to utilize your CPU cache in
         order to gain performance) and you have determined you are willing to trade
         the code clarity, it is recommended that you simply go with type <code class="computeroutput"><span class="keyword">int</span></code> and use some 'magic value' to represent
-        <span class="emphasis"><em>not-an-int</em></span>.
+        <span class="emphasis"><em>not-an-int</em></span>, or use something like <a href="https://github.com/akrzemi1/markable" target="_top"><code class="computeroutput"><span class="identifier">markable</span></code></a> library.
       </p>
 <p>
         Even if you cannot spare any value of <code class="computeroutput"><span class="keyword">int</span></code>
@@ -209,7 +209,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/rebinding_semantics_for_assignment_of_optional_references.html

@@ -135,7 +135,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/relational_operators.html

@@ -99,7 +99,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/type_requirements.html

@@ -95,7 +95,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/boost_optional/tutorial/when_to_use_optional.html

@@ -128,7 +128,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/index.html

@@ -26,7 +26,7 @@
 <span class="firstname">Fernando Luis</span> <span class="surname">Cacciola Carballal</span>
 </h3></div></div>
 <div><p class="copyright">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal</p></div>
-<div><p class="copyright">Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski</p></div>
+<div><p class="copyright">Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski</p></div>
 <div><div class="legalnotice">
 <a name="optional.legal"></a><p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
@@ -62,12 +62,9 @@
 <dt><span class="section"><a href="boost_optional/tutorial/io_operators.html">IO operators</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/optional_references.html">Optional
       references</a></span></dt>
-<dt><span class="section"><a href="boost_optional/tutorial/rebinding_semantics_for_assignment_of_optional_references.html">Rebinding
-      semantics for assignment of optional references</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/in_place_factories.html">In-Place
       Factories</a></span></dt>
-<dt><span class="section"><a href="boost_optional/tutorial/a_note_about_optional_bool_.html">A
-      note about optional&lt;bool&gt;</a></span></dt>
+<dt><span class="section"><a href="boost_optional/tutorial/gotchas.html">Gotchas</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/exception_safety_guarantees.html">Exception
       Safety Guarantees</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/type_requirements.html">Type requirements</a></span></dt>
@@ -146,7 +143,7 @@
 </div>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: October 20, 2015 at 21:17:45 GMT</small></p></td>
+<td align="left"><p><small>Last revised: September 16, 2016 at 23:43:36 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>

doc/html/optional/reference.html

@@ -75,7 +75,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

doc/html/optional/reference/header__boost_optional_optional_hpp_.html

@@ -7,7 +7,7 @@
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../reference.html" title="Reference">
 <link rel="prev" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html" title="Header &lt;boost/optional/optional_fwd.hpp&gt;">
-<link rel="next" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html" title="Detailed Semantics">
+<link rel="next" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html" title="Optional Values">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 <table cellpadding="2" width="100%"><tr>
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -36,134 +36,50 @@
 <span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
 
 <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
-<span class="keyword">class</span> <span class="identifier">optional</span>
-<span class="special">{</span>
-<span class="keyword">public</span> <span class="special">:</span>
+<span class="keyword">class</span> <span class="identifier">optional</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html#reference_operator_template"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="identifier">value_type</span><span class="special">;</span>
+<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
+<span class="keyword">class</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html#reference_operator_template_spec"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="comment">// (If T is of reference type, the parameters and results by reference are by value)</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_not_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_none_t"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&lt;</span>  <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_less_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&gt;</span>  <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_greater_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_move_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&lt;=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_less_or_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="comment">// [new in 1.34]</span>
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_bool_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&gt;=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_greater_or_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_equal_optional_none"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_move_constructor_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_operator_compare_not_equal_optional_none"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_other_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_make_optional_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_move_constructor_other_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_make_optional_bool_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_const_type</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">-&gt;</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_const_type</span><span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_free_get_value_or"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_type</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">-&gt;</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">reference_type</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_free_get_value_or"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_none_t"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_move_equal_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;*</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_move_equal_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">auto</span> <span class="identifier">get_pointer</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_free_get_pointer"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_other_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">auto</span> <span class="identifier">get_pointer</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_free_get_pointer"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_move_equal_other_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">swap</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_swap_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">Args</span><span class="special">...&amp;&amp;</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_emplace"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="identifier">get</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">-&gt;()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">*</span>       <span class="keyword">operator</span> <span class="special">-&gt;()</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">&amp;&amp;</span>      <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_asterisk_move"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">&amp;</span>       <span class="identifier">value</span><span class="special">()</span> <span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">&amp;&amp;</span>      <span class="identifier">value</span><span class="special">()</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value_move"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value_or"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value_or_move"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value_or_call"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">&gt;</span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&amp;&amp;</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_value_or_call_move"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-    <span class="identifier">T</span><span class="special">*</span>       <span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="comment">// deprecated methods</span>
-
-    <span class="comment">// (deprecated)</span>
-    <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_reset"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="comment">// (deprecated)</span>
-    <span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_reset_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="comment">// (deprecated)</span>
-    <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_is_initialized"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-    <span class="comment">// (deprecated)</span>
-    <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="keyword">default</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-<span class="special">};</span>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_not_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&lt;</span>  <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_less_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&gt;</span>  <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_greater_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&lt;=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_less_or_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">&gt;=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_greater_or_equal_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_equal_optional_none"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">!=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_operator_compare_not_equal_optional_none"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_make_optional_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="identifier">make_optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_make_optional_bool_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get_optional_value_or</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;*</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_pointer</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
-
-<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">swap</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html#reference_swap_optional_optional"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">swap</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;&amp;</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html#reference_swap_optional_reference"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
 <span class="special">}</span> <span class="comment">// namespace boost</span>
 </pre>
@@ -171,7 +87,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>
@@ -179,7 +95,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/optional/tutorial.html

@@ -36,12 +36,9 @@
 <dt><span class="section"><a href="../boost_optional/tutorial/io_operators.html">IO operators</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/optional_references.html">Optional
       references</a></span></dt>
-<dt><span class="section"><a href="../boost_optional/tutorial/rebinding_semantics_for_assignment_of_optional_references.html">Rebinding
-      semantics for assignment of optional references</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/in_place_factories.html">In-Place
       Factories</a></span></dt>
-<dt><span class="section"><a href="../boost_optional/tutorial/a_note_about_optional_bool_.html">A
-      note about optional&lt;bool&gt;</a></span></dt>
+<dt><span class="section"><a href="../boost_optional/tutorial/gotchas.html">Gotchas</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/exception_safety_guarantees.html">Exception
       Safety Guarantees</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/type_requirements.html">Type requirements</a></span></dt>
@@ -142,7 +139,7 @@
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 <td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014, 2015 Andrzej Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
         Distributed under the Boost Software License, Version 1.0. (See accompanying
         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
       </p>

include/boost/none.hpp

@@ -1,5 +1,5 @@
 // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
-// Copyright (C) 2014 Andrzej Krzemienski.
+// Copyright (C) 2014, 2015 Andrzej Krzemienski.
 //
 // Distributed under the Boost Software License, Version 1.0.
 // (See accompanying file LICENSE_1_0.txt or copy at

include/boost/none_t.hpp

@@ -1,5 +1,5 @@
 // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
-// Copyright (C) 2014 Andrzej Krzemienski.
+// Copyright (C) 2014, 2015 Andrzej Krzemienski.
 //
 // Use, modification, and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -29,7 +29,7 @@ class none_t {};
 struct none_t
 {
   struct init_tag{};
-  explicit none_t(init_tag){} // to prevent default constructor
+  explicit none_t(init_tag){} // to disable default constructor
 };
 
 #endif // old implementation workarounds
@@ -37,4 +37,3 @@ struct none_t
 } // namespace boost
 
 #endif // header guard
-

include/boost/optional/detail/optional_aligned_storage.hpp

@@ -0,0 +1,75 @@
+// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2016 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_ALIGNED_STORAGE_AJK_12FEB2016_HPP
+#define BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_ALIGNED_STORAGE_AJK_12FEB2016_HPP
+
+namespace boost {
+
+namespace optional_detail {
+// This local class is used instead of that in "aligned_storage.hpp"
+// because I've found the 'official' class to ICE BCB5.5
+// when some types are used with optional<>
+// (due to sizeof() passed down as a non-type template parameter)
+template <class T>
+class aligned_storage
+{
+    // Borland ICEs if unnamed unions are used for this!
+    union
+    // This works around GCC warnings about breaking strict aliasing rules when casting storage address to T*
+#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
+    __attribute__((__may_alias__))
+#endif
+    dummy_u
+    {
+        char data[ sizeof(T) ];
+        BOOST_DEDUCED_TYPENAME type_with_alignment<
+          ::boost::alignment_of<T>::value >::type aligner_;
+    } dummy_ ;
+
+  public:
+
+#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
+    void const* address() const { return &dummy_; }
+    void      * address()       { return &dummy_; }
+#else
+    void const* address() const { return dummy_.data; }
+    void      * address()       { return dummy_.data; }
+#endif
+
+#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
+	// This workaround is supposed to silence GCC warnings about broken strict aliasing rules
+	T const* ptr_ref() const
+	{
+		union { void const* ap_pvoid; T const* as_ptype; } caster = { address() };
+		return caster.as_ptype;
+	}
+	T *      ptr_ref()
+	{
+		union { void* ap_pvoid; T* as_ptype; } caster = { address() };
+		return caster.as_ptype;
+	}
+#else
+	T const* ptr_ref() const { return static_cast<T const*>(address()); }
+	T *      ptr_ref()       { return static_cast<T *>     (address()); }
+#endif
+
+	T const& ref() const { return *ptr_ref(); }
+	T &      ref()       { return *ptr_ref(); }
+  
+} ;
+
+} // namespace optional_detail
+} // namespace boost
+
+#endif // header guard

include/boost/optional/detail/optional_config.hpp

@@ -0,0 +1,99 @@
+// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_CONFIG_AJK_28JAN2015_HPP
+#define BOOST_OPTIONAL_DETAIL_OPTIONAL_CONFIG_AJK_28JAN2015_HPP
+
+#include <boost/config.hpp>
+#include <boost/detail/workaround.hpp>
+
+#if (defined BOOST_NO_CXX11_RVALUE_REFERENCES) || (defined BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES)
+# define BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+#endif
+
+#if BOOST_WORKAROUND(BOOST_INTEL_CXX_VERSION,<=700)
+// AFAICT only Intel 7 correctly resolves the overload set
+// that includes the in-place factory taking functions,
+// so for the other icc versions, in-place factory support
+// is disabled
+# define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
+#endif
+
+#if BOOST_WORKAROUND(__BORLANDC__, <= 0x551)
+// BCB (5.5.1) cannot parse the nested template struct in an inplace factory.
+# define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
+#endif
+
+#if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) \
+    && defined BOOST_BCB_PARTIAL_SPECIALIZATION_BUG
+// BCB (up to 5.64) has the following bug:
+//   If there is a member function/operator template of the form
+//     template<class Expr> mfunc( Expr expr ) ;
+//   some calls are resolved to this even if there are other better matches.
+//   The effect of this bug is that calls to converting ctors and assignments
+//   are incorrectly sink to this general catch-all member function template as shown above.
+# define BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
+#endif
+
+#if defined(__GNUC__) && !defined(__INTEL_COMPILER)
+// GCC since 3.3 has may_alias attribute that helps to alleviate optimizer issues with
+// regard to violation of the strict aliasing rules. The optional< T > storage type is marked
+// with this attribute in order to let the compiler know that it will alias objects of type T
+// and silence compilation warnings.
+# define BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS
+#endif
+
+#if (defined(_MSC_VER) && _MSC_VER <= 1800)
+// on MSCV 2013 and earlier an unwanted temporary is created when you assign from
+// a const lvalue of integral type. Thus we bind not to the original address but
+// to a temporary. 
+# define BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+#endif
+
+#if (defined __GNUC__) && (!defined BOOST_INTEL_CXX_VERSION) && (!defined __clang__)
+// On some GCC versions an unwanted temporary is created when you copy-initialize
+// from a const lvalue of integral type. Thus we bind not to the original address but
+// to a temporary.
+
+# if (__GNUC__ < 4)
+#  define BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+# endif
+
+# if (__GNUC__ == 4 && __GNUC_MINOR__ <= 5)
+#  define BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+# endif
+
+# if (__GNUC__ == 5 && __GNUC_MINOR__ < 2)
+#  define BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+# endif
+
+# if (__GNUC__ == 5 && __GNUC_MINOR__ == 2 && __GNUC_PATCHLEVEL__ == 0)
+#  define BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+# endif
+
+#endif // defined(__GNUC__)
+
+#if (defined __GNUC__) && (!defined BOOST_NO_CXX11_RVALUE_REFERENCES)
+// On some initial rvalue reference implementations GCC does it in a strange way,
+// preferring perfect-forwarding constructor to implicit copy constructor.
+
+# if (__GNUC__ == 4 && __GNUC_MINOR__ == 4)
+#  define BOOST_OPTIONAL_CONFIG_NO_LEGAL_CONVERT_FROM_REF
+# endif
+
+# if (__GNUC__ == 4 && __GNUC_MINOR__ == 5)
+#  define BOOST_OPTIONAL_CONFIG_NO_LEGAL_CONVERT_FROM_REF
+# endif
+
+#endif // defined(__GNUC__)
+
+#endif // header guard

include/boost/optional/detail/optional_factory_support.hpp

@@ -0,0 +1,36 @@
+// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2016 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_FACTORY_SUPPORT_AJK_12FEB2016_HPP
+#define BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_FACTORY_SUPPORT_AJK_12FEB2016_HPP
+
+// Daniel Wallin discovered that bind/apply.hpp badly interacts with the apply<>
+// member template of a factory as used in the optional<> implementation.
+// He proposed this simple fix which is to move the call to apply<> outside
+// namespace boost.
+namespace boost_optional_detail
+{
+  template <class T, class Factory>
+  inline void construct(Factory const& factory, void* address)
+  {
+    factory.BOOST_NESTED_TEMPLATE apply<T>(address);
+  }
+}
+
+namespace boost
+{
+  class in_place_factory_base ;
+  class typed_in_place_factory_base ;
+}
+
+#endif // header guard

include/boost/optional/detail/optional_reference_spec.hpp

@@ -0,0 +1,203 @@
+// Copyright (C) 2015-2016 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP
+#define BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP
+
+#ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+#include <boost/type_traits/is_integral.hpp>
+#include <boost/type_traits/is_const.hpp>
+#endif
+
+# if 1
+
+namespace boost {
+
+namespace detail {
+
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+
+template <class From>
+void prevent_binding_rvalue()
+{
+#ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
+    BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<From>::value, 
+                            "binding rvalue references to optional lvalue references is disallowed");
+#endif    
+}
+
+template <class T>
+BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type& forward_reference(T&& r)
+{
+    BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<T>::value, 
+                            "binding rvalue references to optional lvalue references is disallowed");
+    return boost::forward<T>(r);
+}
+
+#endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+
+template <class From>
+void prevent_assignment_from_false_const_integral()
+{
+#ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
+#ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+    // MSVC compiler without rvalue refernces: we need to disable the asignment from
+    // const integral lvalue reference, as it may be an invalid temporary
+    BOOST_STATIC_ASSERT_MSG(!(boost::is_const<From>::value && boost::is_integral<From>::value), 
+                            "binding const lvalue references to integral types is disabled in this compiler");
+#endif
+#endif   
+}
+
+template <class T>
+struct is_optional_
+{
+  static const bool value = false;
+};
+
+template <class U>
+struct is_optional_< ::boost::optional<U> >
+{
+  static const bool value = true;
+};
+
+template <class T>
+struct is_no_optional
+{
+  static const bool value = !is_optional_<BOOST_DEDUCED_TYPENAME boost::decay<T>::type>::value;
+};
+
+} // namespace detail
+
+template <class T>
+class optional<T&> : public optional_detail::optional_tag
+{
+    T* ptr_;
+    
+public:
+    typedef T& value_type;
+    typedef T& reference_type;
+    typedef T& reference_const_type;
+    typedef T& rval_reference_type;
+    typedef T* pointer_type;
+    typedef T* pointer_const_type;
+    
+    optional() BOOST_NOEXCEPT : ptr_() {}
+    optional(none_t) BOOST_NOEXCEPT : ptr_() {}  
+
+    template <class U>
+        explicit optional(const optional<U&>& rhs) BOOST_NOEXCEPT : ptr_(rhs.ptr_) {}
+    optional(const optional& rhs) BOOST_NOEXCEPT : ptr_(rhs.ptr_) {}
+    
+
+    optional& operator=(const optional& rhs) BOOST_NOEXCEPT { ptr_ = rhs.ptr_; return *this; }
+    template <class U>
+        optional& operator=(const optional<U&>& rhs) BOOST_NOEXCEPT { ptr_ = rhs.ptr_; return *this; }
+    optional& operator=(none_t) BOOST_NOEXCEPT { ptr_ = 0; return *this; }
+    
+    
+    void swap(optional& rhs) BOOST_NOEXCEPT { std::swap(ptr_, rhs.ptr_); }
+    T& get() const { BOOST_ASSERT(ptr_); return   *ptr_; }
+
+    T* get_ptr() const BOOST_NOEXCEPT { return ptr_; }
+    T* operator->() const { BOOST_ASSERT(ptr_); return ptr_; }
+    T& operator*() const { BOOST_ASSERT(ptr_); return *ptr_; }
+    T& value() const { return ptr_ ? *ptr_ : (throw_exception(bad_optional_access()), *ptr_); }
+    
+    bool operator!() const BOOST_NOEXCEPT { return ptr_ == 0; }  
+    BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
+      
+    void reset() BOOST_NOEXCEPT { ptr_ = 0; }
+
+    bool is_initialized() const BOOST_NOEXCEPT { return ptr_ != 0; }
+    
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES   
+ 
+    template <class R>
+        optional(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
+        : ptr_(boost::addressof(r)) { detail::prevent_binding_rvalue<R>(); }
+        
+    template <class R>
+        optional(bool cond, R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
+        : ptr_(cond ? boost::addressof(r) : 0) { detail::prevent_binding_rvalue<R>(); }
+        
+    template <class R>
+        BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, optional<T&>&>::type
+        operator=(R&& r) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); return *this; }
+        
+    template <class R>
+        void emplace(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
+        { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); }
+        
+    template <class R>
+      T& get_value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) const BOOST_NOEXCEPT
+      { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; }
+      
+    template <class R>
+        T& value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) const BOOST_NOEXCEPT
+        { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; }
+        
+    template <class R>
+      void reset(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
+      { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); }
+      
+    template <class F>
+        T& value_or_eval(F f) const { return ptr_ ? *ptr_ : detail::forward_reference(f()); }
+      
+#else  // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+
+    template <class U>
+        optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(boost::addressof(v)) { }
+        
+    template <class U>
+        optional(bool cond, U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(v) : 0) {}
+
+    template <class U>
+        BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, optional<T&>&>::type
+        operator=(U& v) BOOST_NOEXCEPT
+        {
+            detail::prevent_assignment_from_false_const_integral<U>();
+            ptr_ = boost::addressof(v); return *this;
+        }
+
+    template <class U>
+        void emplace(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT
+        { ptr_ = boost::addressof(v); }
+        
+    template <class U>
+      T& get_value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) const BOOST_NOEXCEPT
+      { return ptr_ ? *ptr_ : v; }
+      
+    template <class U>
+        T& value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) const BOOST_NOEXCEPT
+        { return ptr_ ? *ptr_ : v; }
+        
+    template <class U>
+      void reset(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT
+      { ptr_ = boost::addressof(v); }
+      
+    template <class F>
+      T& value_or_eval(F f) const { return ptr_ ? *ptr_ : f(); }
+      
+#endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+};
+
+template <class T> 
+  void swap ( optional<T&>& x, optional<T&>& y) BOOST_NOEXCEPT
+{
+  x.swap(y);
+}
+
+} // namespace boost
+
+#endif // 1/0
+
+#endif // header guard

include/boost/optional/detail/optional_relops.hpp

@@ -0,0 +1,196 @@
+// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_RELOPS_AJK_03OCT2015_HPP
+#define BOOST_OPTIONAL_DETAIL_OPTIONAL_RELOPS_AJK_03OCT2015_HPP
+
+namespace boost {
+
+// optional's relational operators ( ==, !=, <, >, <=, >= ) have deep-semantics (compare values).
+// WARNING: This is UNLIKE pointers. Use equal_pointees()/less_pointess() in generic code instead.
+
+
+//
+// optional<T> vs optional<T> cases
+//
+
+template<class T>
+inline
+bool operator == ( optional<T> const& x, optional<T> const& y )
+{ return equal_pointees(x,y); }
+
+template<class T>
+inline
+bool operator < ( optional<T> const& x, optional<T> const& y )
+{ return less_pointees(x,y); }
+
+template<class T>
+inline
+bool operator != ( optional<T> const& x, optional<T> const& y )
+{ return !( x == y ) ; }
+
+template<class T>
+inline
+bool operator > ( optional<T> const& x, optional<T> const& y )
+{ return y < x ; }
+
+template<class T>
+inline
+bool operator <= ( optional<T> const& x, optional<T> const& y )
+{ return !( y < x ) ; }
+
+template<class T>
+inline
+bool operator >= ( optional<T> const& x, optional<T> const& y )
+{ return !( x < y ) ; }
+
+
+//
+// optional<T> vs T cases
+//
+template<class T>
+inline
+bool operator == ( optional<T> const& x, T const& y )
+{ return equal_pointees(x, optional<T>(y)); }
+
+template<class T>
+inline
+bool operator < ( optional<T> const& x, T const& y )
+{ return less_pointees(x, optional<T>(y)); }
+
+template<class T>
+inline
+bool operator != ( optional<T> const& x, T const& y )
+{ return !( x == y ) ; }
+
+template<class T>
+inline
+bool operator > ( optional<T> const& x, T const& y )
+{ return y < x ; }
+
+template<class T>
+inline
+bool operator <= ( optional<T> const& x, T const& y )
+{ return !( y < x ) ; }
+
+template<class T>
+inline
+bool operator >= ( optional<T> const& x, T const& y )
+{ return !( x < y ) ; }
+
+//
+// T vs optional<T> cases
+//
+
+template<class T>
+inline
+bool operator == ( T const& x, optional<T> const& y )
+{ return equal_pointees( optional<T>(x), y ); }
+
+template<class T>
+inline
+bool operator < ( T const& x, optional<T> const& y )
+{ return less_pointees( optional<T>(x), y ); }
+
+template<class T>
+inline
+bool operator != ( T const& x, optional<T> const& y )
+{ return !( x == y ) ; }
+
+template<class T>
+inline
+bool operator > ( T const& x, optional<T> const& y )
+{ return y < x ; }
+
+template<class T>
+inline
+bool operator <= ( T const& x, optional<T> const& y )
+{ return !( y < x ) ; }
+
+template<class T>
+inline
+bool operator >= ( T const& x, optional<T> const& y )
+{ return !( x < y ) ; }
+
+
+//
+// optional<T> vs none cases
+//
+
+template<class T>
+inline
+bool operator == ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
+{ return !x; }
+
+template<class T>
+inline
+bool operator < ( optional<T> const& x, none_t )
+{ return less_pointees(x,optional<T>() ); }
+
+template<class T>
+inline
+bool operator != ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
+{ return bool(x); }
+
+template<class T>
+inline
+bool operator > ( optional<T> const& x, none_t y )
+{ return y < x ; }
+
+template<class T>
+inline
+bool operator <= ( optional<T> const& x, none_t y )
+{ return !( y < x ) ; }
+
+template<class T>
+inline
+bool operator >= ( optional<T> const& x, none_t y )
+{ return !( x < y ) ; }
+
+//
+// none vs optional<T> cases
+//
+
+template<class T>
+inline
+bool operator == ( none_t , optional<T> const& y ) BOOST_NOEXCEPT
+{ return !y; }
+
+template<class T>
+inline
+bool operator < ( none_t , optional<T> const& y )
+{ return less_pointees(optional<T>() ,y); }
+
+template<class T>
+inline
+bool operator != ( none_t, optional<T> const& y ) BOOST_NOEXCEPT
+{ return bool(y); }
+
+template<class T>
+inline
+bool operator > ( none_t x, optional<T> const& y )
+{ return y < x ; }
+
+template<class T>
+inline
+bool operator <= ( none_t x, optional<T> const& y )
+{ return !( y < x ) ; }
+
+template<class T>
+inline
+bool operator >= ( none_t x, optional<T> const& y )
+{ return !( x < y ) ; }
+
+} // namespace boost
+
+#endif // header guard
+

include/boost/optional/detail/optional_swap.hpp

@@ -0,0 +1,117 @@
+// Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_SWAP_AJK_28JAN2015_HPP
+#define BOOST_OPTIONAL_DETAIL_OPTIONAL_SWAP_AJK_28JAN2015_HPP
+
+#include <boost/core/swap.hpp>
+#include <boost/optional/optional_fwd.hpp>
+
+namespace boost {
+
+namespace optional_detail {
+
+template <bool use_default_constructor> struct swap_selector;
+
+template <>
+struct swap_selector<true>
+{
+    template <class T>
+    static void optional_swap ( optional<T>& x, optional<T>& y )
+    {
+        const bool hasX = !!x;
+        const bool hasY = !!y;
+
+        if ( !hasX && !hasY )
+            return;
+
+        if( !hasX )
+            x.emplace();
+        else if ( !hasY )
+            y.emplace();
+
+        // Boost.Utility.Swap will take care of ADL and workarounds for broken compilers
+        boost::swap(x.get(), y.get());
+
+        if( !hasX )
+            y = boost::none ;
+        else if( !hasY )
+            x = boost::none ;
+    }
+};
+
+#ifdef BOOST_OPTIONAL_DETAIL_MOVE
+# undef BOOST_OPTIONAL_DETAIL_MOVE
+#endif
+
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+# define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) boost::move(EXPR_)
+#else
+# define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) EXPR_
+#endif
+
+template <>
+struct swap_selector<false>
+{
+    template <class T>
+    static void optional_swap ( optional<T>& x, optional<T>& y ) 
+    //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
+    {
+        if (x)
+        {
+            if (y)
+            {
+                boost::swap(*x, *y);
+            }
+            else
+            {
+                y = BOOST_OPTIONAL_DETAIL_MOVE(*x);
+                x = boost::none;
+            }
+        }
+        else
+        {
+            if (y)
+            {
+                x = BOOST_OPTIONAL_DETAIL_MOVE(*y);
+                y = boost::none;
+            }
+        }
+    }
+};
+
+} // namespace optional_detail
+
+#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_CONFIG_RESTORE_OBSOLETE_SWAP_IMPLEMENTATION)
+
+template<class T>
+struct optional_swap_should_use_default_constructor : boost::false_type {} ;
+
+#else
+
+template<class T>
+struct optional_swap_should_use_default_constructor : has_nothrow_default_constructor<T> {} ;
+
+#endif
+
+template <class T>
+inline void swap ( optional<T>& x, optional<T>& y )
+//BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
+{
+    optional_detail::swap_selector<optional_swap_should_use_default_constructor<T>::value>::optional_swap(x, y);
+}
+
+} // namespace boost
+
+#undef BOOST_OPTIONAL_DETAIL_MOVE
+
+#endif // header guard

include/boost/optional/optional.hpp

@@ -20,7 +20,6 @@
 #include <new>
 #include <iosfwd>
 
-#include <boost/config.hpp>
 #include <boost/assert.hpp>
 #include <boost/core/addressof.hpp>
 #include <boost/core/enable_if.hpp>
@@ -31,208 +30,60 @@
 #include <boost/throw_exception.hpp>
 #include <boost/type.hpp>
 #include <boost/type_traits/alignment_of.hpp>
+#include <boost/type_traits/conditional.hpp>
 #include <boost/type_traits/has_nothrow_constructor.hpp>
 #include <boost/type_traits/type_with_alignment.hpp>
 #include <boost/type_traits/remove_const.hpp>
 #include <boost/type_traits/remove_reference.hpp>
 #include <boost/type_traits/decay.hpp>
 #include <boost/type_traits/is_base_of.hpp>
+#include <boost/type_traits/is_constructible.hpp>
 #include <boost/type_traits/is_lvalue_reference.hpp>
 #include <boost/type_traits/is_nothrow_move_assignable.hpp>
 #include <boost/type_traits/is_nothrow_move_constructible.hpp>
-#include <boost/type_traits/is_reference.hpp>
 #include <boost/type_traits/is_rvalue_reference.hpp>
 #include <boost/type_traits/is_same.hpp>
-#include <boost/mpl/if.hpp>
-#include <boost/mpl/bool.hpp>
-#include <boost/mpl/not.hpp>
-#include <boost/detail/reference_content.hpp>
 #include <boost/move/utility.hpp>
 #include <boost/none.hpp>
 #include <boost/utility/compare_pointees.hpp>
 
 #include <boost/optional/optional_fwd.hpp>
+#include <boost/optional/detail/optional_config.hpp>
+#include <boost/optional/detail/optional_factory_support.hpp>
+#include <boost/optional/detail/optional_aligned_storage.hpp>
 
-#if (defined BOOST_NO_CXX11_RVALUE_REFERENCES) || (defined BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES)
-#define BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-#endif
-
-#if BOOST_WORKAROUND(BOOST_INTEL_CXX_VERSION,<=700)
-// AFAICT only Intel 7 correctly resolves the overload set
-// that includes the in-place factory taking functions,
-// so for the other icc versions, in-place factory support
-// is disabled
-#define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
-#endif
-
-#if BOOST_WORKAROUND(__BORLANDC__, <= 0x551)
-// BCB (5.5.1) cannot parse the nested template struct in an inplace factory.
-#define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
-#endif
-
-#if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) \
-    && BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x581) )
-// BCB (up to 5.64) has the following bug:
-//   If there is a member function/operator template of the form
-//     template<class Expr> mfunc( Expr expr ) ;
-//   some calls are resolved to this even if there are other better matches.
-//   The effect of this bug is that calls to converting ctors and assignments
-//   are incrorrectly sink to this general catch-all member function template as shown above.
-#define BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
-#endif
-
-#if defined(__GNUC__) && !defined(__INTEL_COMPILER)
-// GCC since 3.3 has may_alias attribute that helps to alleviate optimizer issues with
-// regard to violation of the strict aliasing rules. The optional< T > storage type is marked
-// with this attribute in order to let the compiler know that it will alias objects of type T
-// and silence compilation warnings.
-#define BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS
-#endif
-
-// Daniel Wallin discovered that bind/apply.hpp badly interacts with the apply<>
-// member template of a factory as used in the optional<> implementation.
-// He proposed this simple fix which is to move the call to apply<> outside
-// namespace boost.
-namespace boost_optional_detail
-{
-  template <class T, class Factory>
-  inline void construct(Factory const& factory, void* address)
-  {
-    factory.BOOST_NESTED_TEMPLATE apply<T>(address);
-  }
-}
-
-
+#ifdef BOOST_OPTIONAL_CONFIG_USE_OLD_IMPLEMENTATION_OF_OPTIONAL
+#include <boost/optional/detail/old_optional_implementation.hpp>
+#else
 namespace boost {
 
-class in_place_factory_base ;
-class typed_in_place_factory_base ;
-
-// This forward is needed to refer to namespace scope swap from the member swap
-template<class T> void swap ( optional<T>& x, optional<T>& y );
-
 namespace optional_detail {
-// This local class is used instead of that in "aligned_storage.hpp"
-// because I've found the 'official' class to ICE BCB5.5
-// when some types are used with optional<>
-// (due to sizeof() passed down as a non-type template parameter)
-template <class T>
-class aligned_storage
-{
-    // Borland ICEs if unnamed unions are used for this!
-    union
-    // This works around GCC warnings about breaking strict aliasing rules when casting storage address to T*
-#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
-    __attribute__((__may_alias__))
-#endif
-    dummy_u
-    {
-        char data[ sizeof(T) ];
-        BOOST_DEDUCED_TYPENAME type_with_alignment<
-          ::boost::alignment_of<T>::value >::type aligner_;
-    } dummy_ ;
-
-  public:
-
-#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
-    void const* address() const { return &dummy_; }
-    void      * address()       { return &dummy_; }
-#else
-    void const* address() const { return dummy_.data; }
-    void      * address()       { return dummy_.data; }
-#endif
-} ;
-
-template<class T>
-struct types_when_isnt_ref
-{
-  typedef T const& reference_const_type ;
-  typedef T &      reference_type ;
-#ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-  typedef T &&     rval_reference_type ;
-  typedef T &&     reference_type_of_temporary_wrapper;
-#ifdef BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES
-  // GCC 4.4 has support for an early draft of rvalue references. The conforming version below
-  // causes warnings about returning references to a temporary.
-  static T&& move(T&& r) { return r; }
-#else
-  static rval_reference_type move(reference_type r) { return boost::move(r); }
-#endif
-#endif
-  typedef T const* pointer_const_type ;
-  typedef T *      pointer_type ;
-  typedef T const& argument_type ;
-} ;
-
-template<class T>
-struct types_when_is_ref
-{
-  typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type raw_type ;
-
-  typedef raw_type&  reference_const_type ;
-  typedef raw_type&  reference_type ;
-#ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-  typedef BOOST_DEDUCED_TYPENAME remove_const<raw_type>::type&& rval_reference_type ;
-  typedef raw_type&  reference_type_of_temporary_wrapper;
-  static reference_type move(reference_type r) { return r; }
-#endif
-  typedef raw_type*  pointer_const_type ;
-  typedef raw_type*  pointer_type ;
-  typedef raw_type&  argument_type ;
-} ;
-
-template <class To, class From>
-void prevent_binding_rvalue_ref_to_optional_lvalue_ref()
-{
-#ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
-  BOOST_STATIC_ASSERT_MSG(
-    !boost::is_lvalue_reference<To>::value || !boost::is_rvalue_reference<From>::value, 
-    "binding rvalue references to optional lvalue references is disallowed");
-#endif    
-}
 
 struct optional_tag {} ;
 
+
 template<class T>
 class optional_base : public optional_tag
 {
   private :
 
-    typedef
-#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
-    BOOST_DEDUCED_TYPENAME
-#endif
-    ::boost::detail::make_reference_content<T>::type internal_type ;
-
-    typedef aligned_storage<internal_type> storage_type ;
-
-    typedef types_when_isnt_ref<T> types_when_not_ref ;
-    typedef types_when_is_ref<T>   types_when_ref   ;
-
+    typedef aligned_storage<T> storage_type ;
     typedef optional_base<T> this_type ;
 
   protected :
 
     typedef T value_type ;
 
-    typedef mpl::true_  is_reference_tag ;
-    typedef mpl::false_ is_not_reference_tag ;
-
-    typedef BOOST_DEDUCED_TYPENAME is_reference<T>::type is_reference_predicate ;
-
-  public:
-    typedef BOOST_DEDUCED_TYPENAME mpl::if_<is_reference_predicate,types_when_ref,types_when_not_ref>::type types ;
-
   protected:
-    typedef BOOST_DEDUCED_TYPENAME types::reference_type       reference_type ;
-    typedef BOOST_DEDUCED_TYPENAME types::reference_const_type reference_const_type ;
+    typedef T &       reference_type ;
+    typedef T const&  reference_const_type ;
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-    typedef BOOST_DEDUCED_TYPENAME types::rval_reference_type  rval_reference_type ;
-    typedef BOOST_DEDUCED_TYPENAME types::reference_type_of_temporary_wrapper reference_type_of_temporary_wrapper ;
+    typedef T &&  rval_reference_type ;
+    typedef T &&  reference_type_of_temporary_wrapper ;
 #endif
-    typedef BOOST_DEDUCED_TYPENAME types::pointer_type         pointer_type ;
-    typedef BOOST_DEDUCED_TYPENAME types::pointer_const_type   pointer_const_type ;
-    typedef BOOST_DEDUCED_TYPENAME types::argument_type        argument_type ;
+    typedef T *         pointer_type ;
+    typedef T const*    pointer_const_type ;
+    typedef T const&    argument_type ;
 
     // Creates an optional<T> uninitialized.
     // No-throw
@@ -252,7 +103,7 @@ class optional_base : public optional_tag
       :
       m_initialized(false)
     {
-      construct(val);
+        construct(val);
     }
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
@@ -332,7 +183,7 @@ class optional_base : public optional_tag
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
-             assign_value(rhs.get_impl(), is_reference_predicate() );
+             assign_value(rhs.get_impl());
         else destroy();
       }
       else
@@ -349,7 +200,7 @@ class optional_base : public optional_tag
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
-             assign_value(boost::move(rhs.get_impl()), is_reference_predicate() );
+             assign_value( boost::move(rhs.get_impl()) );
         else destroy();
       }
       else
@@ -368,9 +219,9 @@ class optional_base : public optional_tag
       {
         if ( rhs.is_initialized() )
 #ifndef BOOST_OPTIONAL_CONFIG_RESTORE_ASSIGNMENT_OF_NONCONVERTIBLE_TYPES
-          assign_value(rhs.get(), is_reference_predicate() );
+          assign_value( rhs.get() );
 #else
-          assign_value(static_cast<value_type>(rhs.get()), is_reference_predicate() );
+          assign_value( static_cast<value_type>(rhs.get()) );
 #endif
           
         else destroy();
@@ -395,7 +246,7 @@ class optional_base : public optional_tag
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
-             assign_value(static_cast<ref_type>(rhs.get()), is_reference_predicate() );
+             assign_value( static_cast<ref_type>(rhs.get()) );
         else destroy();
       }
       else
@@ -410,7 +261,7 @@ class optional_base : public optional_tag
     void assign ( argument_type val )
     {
       if (is_initialized())
-           assign_value(val, is_reference_predicate() );
+           assign_value(val);
       else construct(val);
     }
     
@@ -419,7 +270,7 @@ class optional_base : public optional_tag
     void assign ( rval_reference_type val )
     {
       if (is_initialized())
-           assign_value( boost::move(val), is_reference_predicate() );
+           assign_value( boost::move(val) );
       else construct( boost::move(val) );
     }
 #endif
@@ -471,14 +322,14 @@ class optional_base : public optional_tag
 
     void construct ( argument_type val )
      {
-       ::new (m_storage.address()) internal_type(val) ;
+       ::new (m_storage.address()) value_type(val) ;
        m_initialized = true ;
      }
      
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     void construct ( rval_reference_type val )
      {
-       ::new (m_storage.address()) internal_type( types::move(val) ) ;
+       ::new (m_storage.address()) value_type( boost::move(val) ) ;
        m_initialized = true ;
      }
 #endif
@@ -491,7 +342,7 @@ class optional_base : public optional_tag
     void emplace_assign ( Args&&... args )
      {
        destroy();
-       ::new (m_storage.address()) internal_type( boost::forward<Args>(args)... );
+       ::new (m_storage.address()) value_type( boost::forward<Args>(args)... );
        m_initialized = true ;
      }
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
@@ -499,14 +350,14 @@ class optional_base : public optional_tag
     void emplace_assign ( Arg&& arg )
      {
        destroy();
-       ::new (m_storage.address()) internal_type( boost::forward<Arg>(arg) );
+       ::new (m_storage.address()) value_type( boost::forward<Arg>(arg) );
        m_initialized = true ;
      }
      
     void emplace_assign ()
      {
        destroy();
-       ::new (m_storage.address()) internal_type();
+       ::new (m_storage.address()) value_type();
        m_initialized = true ;
      }
 #else
@@ -514,7 +365,7 @@ class optional_base : public optional_tag
     void emplace_assign ( const Arg& arg )
      {
        destroy();
-       ::new (m_storage.address()) internal_type( arg );
+       ::new (m_storage.address()) value_type( arg );
        m_initialized = true ;
      }
      
@@ -522,14 +373,14 @@ class optional_base : public optional_tag
     void emplace_assign ( Arg& arg )
      {
        destroy();
-       ::new (m_storage.address()) internal_type( arg );
+       ::new (m_storage.address()) value_type( arg );
        m_initialized = true ;
      }
      
     void emplace_assign ()
      {
        destroy();
-       ::new (m_storage.address()) internal_type();
+       ::new (m_storage.address()) value_type();
        m_initialized = true ;
      }
 #endif
@@ -541,7 +392,6 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr&& factory, in_place_factory_base const* )
      {
-       BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
        boost_optional_detail::construct<value_type>(factory, m_storage.address());
        m_initialized = true ;
      }
@@ -550,7 +400,6 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr&& factory, typed_in_place_factory_base const* )
      {
-       BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
        factory.apply(m_storage.address()) ;
        m_initialized = true ;
      }
@@ -575,7 +424,6 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr const& factory, in_place_factory_base const* )
      {
-       BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
        boost_optional_detail::construct<value_type>(factory, m_storage.address());
        m_initialized = true ;
      }
@@ -584,7 +432,6 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr const& factory, typed_in_place_factory_base const* )
      {
-       BOOST_STATIC_ASSERT ( ::boost::mpl::not_<is_reference_predicate>::value ) ;
        factory.apply(m_storage.address()) ;
        m_initialized = true ;
      }
@@ -615,7 +462,7 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr&& expr, void const* )
     {
-      new (m_storage.address()) internal_type(boost::forward<Expr>(expr)) ;
+      new (m_storage.address()) value_type(boost::forward<Expr>(expr)) ;
       m_initialized = true ;
     }
 
@@ -626,7 +473,7 @@ class optional_base : public optional_tag
     template<class Expr>
     void assign_expr_to_initialized ( Expr&& expr, void const* )
     {
-      assign_value(boost::forward<Expr>(expr), is_reference_predicate());
+      assign_value( boost::forward<Expr>(expr) );
     }
 #else
     // Constructs using any expression implicitly convertible to the single argument
@@ -636,7 +483,7 @@ class optional_base : public optional_tag
     template<class Expr>
     void construct ( Expr const& expr, void const* )
      {
-       new (m_storage.address()) internal_type(expr) ;
+       new (m_storage.address()) value_type(expr) ;
        m_initialized = true ;
      }
 
@@ -647,7 +494,7 @@ class optional_base : public optional_tag
     template<class Expr>
     void assign_expr_to_initialized ( Expr const& expr, void const* )
      {
-       assign_value(expr, is_reference_predicate());
+       assign_value(expr);
      }
 
 #endif
@@ -674,7 +521,7 @@ class optional_base : public optional_tag
        {
          // An exception can be thrown here.
          // It it happens, THIS will be left uninitialized.
-         new (m_storage.address()) internal_type(types::move(expr.get())) ;
+         new (m_storage.address()) value_type(boost::move(expr.get())) ;
          m_initialized = true ;
        }
      }
@@ -687,78 +534,78 @@ class optional_base : public optional_tag
        {
          // An exception can be thrown here.
          // It it happens, THIS will be left uninitialized.
-         new (m_storage.address()) internal_type(expr.get()) ;
+         new (m_storage.address()) value_type(expr.get()) ;
          m_initialized = true ;
        }
      }
 #endif
 #endif // defined BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
 
-    void assign_value ( argument_type val, is_not_reference_tag ) { get_impl() = val; }
-    void assign_value ( argument_type val, is_reference_tag     ) { construct(val); }
+    void assign_value ( argument_type val ) { get_impl() = val; }
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-    void assign_value ( rval_reference_type val, is_not_reference_tag ) { get_impl() = static_cast<rval_reference_type>(val); }
-    void assign_value ( rval_reference_type val, is_reference_tag     ) { construct( static_cast<rval_reference_type>(val) ); }
+    void assign_value ( rval_reference_type val ) { get_impl() = static_cast<rval_reference_type>(val); }
 #endif
 
     void destroy()
     {
       if ( m_initialized )
-        destroy_impl(is_reference_predicate()) ;
+        destroy_impl() ;
     }
 
-    reference_const_type get_impl() const { return dereference(get_object(), is_reference_predicate() ) ; }
-    reference_type       get_impl()       { return dereference(get_object(), is_reference_predicate() ) ; }
+    reference_const_type get_impl() const { return m_storage.ref() ; }
+    reference_type       get_impl()       { return m_storage.ref() ; }
 
-    pointer_const_type get_ptr_impl() const { return cast_ptr(get_object(), is_reference_predicate() ) ; }
-    pointer_type       get_ptr_impl()       { return cast_ptr(get_object(), is_reference_predicate() ) ; }
+    pointer_const_type get_ptr_impl() const { return m_storage.ptr_ref(); }
+    pointer_type       get_ptr_impl()       { return m_storage.ptr_ref(); }
 
   private :
 
-    // internal_type can be either T or reference_content<T>
-#if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
-    // This workaround is supposed to silence GCC warnings about broken strict aliasing rules
-    internal_type const* get_object() const
-    {
-        union { void const* ap_pvoid; internal_type const* as_ptype; } caster = { m_storage.address() };
-        return caster.as_ptype;
-    }
-    internal_type *      get_object()
-    {
-        union { void* ap_pvoid; internal_type* as_ptype; } caster = { m_storage.address() };
-        return caster.as_ptype;
-    }
+#if BOOST_WORKAROUND(BOOST_MSVC, <= 1600)
+    void destroy_impl ( ) { m_storage.ptr_ref()->~T() ; m_initialized = false ; }
 #else
-    internal_type const* get_object() const { return static_cast<internal_type const*>(m_storage.address()); }
-    internal_type *      get_object()       { return static_cast<internal_type *>     (m_storage.address()); }
+    void destroy_impl ( ) { m_storage.ref().T::~T() ; m_initialized = false ; }
 #endif
 
-    // reference_content<T> lacks an implicit conversion to T&, so the following is needed to obtain a proper reference.
-    reference_const_type dereference( internal_type const* p, is_not_reference_tag ) const { return *p ; }
-    reference_type       dereference( internal_type*       p, is_not_reference_tag )       { return *p ; }
-    reference_const_type dereference( internal_type const* p, is_reference_tag     ) const { return p->get() ; }
-    reference_type       dereference( internal_type*       p, is_reference_tag     )       { return p->get() ; }
-
-#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x581))
-    void destroy_impl ( is_not_reference_tag ) { get_ptr_impl()->internal_type::~internal_type() ; m_initialized = false ; }
-#else
-    void destroy_impl ( is_not_reference_tag ) { get_ptr_impl()->~T() ; m_initialized = false ; }
-#endif
-
-    void destroy_impl ( is_reference_tag     ) { m_initialized = false ; }
-
-    // If T is of reference type, trying to get a pointer to the held value must result in a compile-time error.
-    // Decent compilers should disallow conversions from reference_content<T>* to T*, but just in case,
-    // the following olverloads are used to filter out the case and guarantee an error in case of T being a reference.
-    pointer_const_type cast_ptr( internal_type const* p, is_not_reference_tag ) const { return p ; }
-    pointer_type       cast_ptr( internal_type *      p, is_not_reference_tag )       { return p ; }
-    pointer_const_type cast_ptr( internal_type const* p, is_reference_tag     ) const { return &p->get() ; }
-    pointer_type       cast_ptr( internal_type *      p, is_reference_tag     )       { return &p->get() ; }
-
     bool m_initialized ;
     storage_type m_storage ;
 } ;
 
+// definition of metafunciton is_optional_val_init_candidate
+template <typename U>
+struct is_optional_related
+  : boost::conditional< boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
+                     || boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, none_t>::value,
+    boost::true_type, boost::false_type>::type
+{};
+
+#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) && !BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500) && !defined(__SUNPRO_CC)
+  // this condition is a copy paste from is_constructible.hpp
+  // I also disable SUNPRO, as it seems not to support type_traits correctly
+  
+template <typename T, typename U>
+struct is_convertible_to_T_or_factory
+  : boost::conditional< boost::is_base_of<boost::in_place_factory_base, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
+                     || boost::is_base_of<boost::typed_in_place_factory_base, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
+                     || boost::is_constructible<T, U&&>::value
+                      , boost::true_type, boost::false_type>::type
+{};
+
+#else
+
+#define BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
+
+template <typename, typename>
+struct is_convertible_to_T_or_factory : boost::true_type
+{};
+
+#endif // is_convertible condition
+
+template <typename T, typename U>
+struct is_optional_val_init_candidate
+  : boost::conditional< !is_optional_related<U>::value && is_convertible_to_T_or_factory<T, U>::value
+                      , boost::true_type, boost::false_type>::type
+{};
+    
 } // namespace optional_detail
 
 template<class T>
@@ -797,7 +644,7 @@ class optional : public optional_detail::optional_base<T>
     // Creates an optional<T> initialized with 'move(val)'.
     // Can throw if T::T(T &&) does
     optional ( rval_reference_type val ) : base( boost::forward<T>(val) ) 
-      {optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();}
+      {}
 #endif
 
     // Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialized optional.
@@ -847,12 +694,10 @@ class optional : public optional_detail::optional_base<T>
 
   template<class Expr>
   explicit optional ( Expr&& expr, 
-                      BOOST_DEDUCED_TYPENAME boost::disable_if_c<
-                        (boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value) || 
-                        boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value >::type* = 0 
+                      BOOST_DEDUCED_TYPENAME boost::enable_if< optional_detail::is_optional_val_init_candidate<T, Expr> >::type* = 0 
   ) 
     : base(boost::forward<Expr>(expr),boost::addressof(expr)) 
-    {optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();}
+    {}
 
 #else
     template<class Expr>
@@ -873,23 +718,22 @@ class optional : public optional_detail::optional_base<T>
 	{}
 
 #endif
-   // No-throw (assuming T::~T() doesn't)
-    ~optional() {}
 
+#if BOOST_WORKAROUND(_MSC_VER, <= 1600)
+    //  On old MSVC compilers the implicitly declared dtor is not called
+    ~optional() {}
+#endif
+
+	
 #if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) && !defined(BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION)
     // Assigns from an expression. See corresponding constructor.
     // Basic Guarantee: If the resolved T ctor throws, this is left UNINITIALIZED
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
     template<class Expr>
-    BOOST_DEDUCED_TYPENAME boost::disable_if_c<
-      boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value || 
-        boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value,
-      optional&
-    >::type 
+    BOOST_DEDUCED_TYPENAME boost::enable_if<optional_detail::is_optional_val_init_candidate<T, Expr>, optional&>::type 
     operator= ( Expr&& expr )
       {
-        optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();
         this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr));
         return *this ;
       }
@@ -957,7 +801,6 @@ class optional : public optional_detail::optional_base<T>
     // Assigns from a T (deep-moves the rhs value)
     optional& operator= ( rval_reference_type val )
       {
-        optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();
         this->assign( boost::move(val) ) ;
         return *this ;
       }
@@ -1040,7 +883,7 @@ class optional : public optional_detail::optional_base<T>
 #if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
     reference_const_type operator *() const& { return this->get() ; }
     reference_type       operator *() &      { return this->get() ; }
-    reference_type_of_temporary_wrapper operator *() && { return base::types::move(this->get()) ; }
+    reference_type_of_temporary_wrapper operator *() && { return boost::move(this->get()) ; }
 #else
     reference_const_type operator *() const { return this->get() ; }
     reference_type       operator *()       { return this->get() ; }
@@ -1066,7 +909,7 @@ class optional : public optional_detail::optional_base<T>
     reference_type_of_temporary_wrapper value() &&
       { 
         if (this->is_initialized())
-          return base::types::move(this->get()) ;
+          return boost::move(this->get()) ;
         else
           throw_exception(bad_optional_access());
       }
@@ -1104,7 +947,7 @@ class optional : public optional_detail::optional_base<T>
     value_type value_or ( U&& v ) && 
       { 
         if (this->is_initialized())
-          return base::types::move(get());
+          return boost::move(get());
         else
           return boost::forward<U>(v);
       }
@@ -1152,7 +995,7 @@ class optional : public optional_detail::optional_base<T>
     value_type value_or_eval ( F f ) &&
       {
         if (this->is_initialized())
-          return base::types::move(get());
+          return boost::move(get());
         else
           return f();
       }
@@ -1172,6 +1015,12 @@ class optional : public optional_detail::optional_base<T>
     BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
 } ;
 
+} // namespace boost
+
+#endif // BOOST_OPTIONAL_CONFIG_USE_OLD_IMPLEMENTATION_OF_OPTIONAL
+
+namespace boost {
+  
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 template<class T>
 class optional<T&&>
@@ -1180,6 +1029,14 @@ class optional<T&&>
 } ;
 #endif
 
+} // namespace boost
+
+#ifndef BOOST_OPTIONAL_CONFIG_DONT_SPECIALIZE_OPTIONAL_REFS
+# include <boost/optional/detail/optional_reference_spec.hpp>
+#endif
+
+namespace boost {
+
 // Returns optional<T>(v)
 template<class T>
 inline
@@ -1268,6 +1125,10 @@ get_pointer ( optional<T>& opt )
   return opt.get_ptr() ;
 }
 
+} // namespace boost
+
+namespace boost {
+  
 // The following declaration prevents a bug where operator safe-bool is used upon streaming optional object if you forget the IO header.
 template<class CharType, class CharTrait>
 std::basic_ostream<CharType, CharTrait>&
@@ -1277,291 +1138,9 @@ operator<<(std::basic_ostream<CharType, CharTrait>& os, optional_detail::optiona
   return os;  
 }
 
-// optional's relational operators ( ==, !=, <, >, <=, >= ) have deep-semantics (compare values).
-// WARNING: This is UNLIKE pointers. Use equal_pointees()/less_pointess() in generic code instead.
-
-
-//
-// optional<T> vs optional<T> cases
-//
-
-template<class T>
-inline
-bool operator == ( optional<T> const& x, optional<T> const& y )
-{ return equal_pointees(x,y); }
-
-template<class T>
-inline
-bool operator < ( optional<T> const& x, optional<T> const& y )
-{ return less_pointees(x,y); }
-
-template<class T>
-inline
-bool operator != ( optional<T> const& x, optional<T> const& y )
-{ return !( x == y ) ; }
-
-template<class T>
-inline
-bool operator > ( optional<T> const& x, optional<T> const& y )
-{ return y < x ; }
-
-template<class T>
-inline
-bool operator <= ( optional<T> const& x, optional<T> const& y )
-{ return !( y < x ) ; }
-
-template<class T>
-inline
-bool operator >= ( optional<T> const& x, optional<T> const& y )
-{ return !( x < y ) ; }
-
-
-//
-// optional<T> vs T cases
-//
-template<class T>
-inline
-bool operator == ( optional<T> const& x, T const& y )
-{ return equal_pointees(x, optional<T>(y)); }
-
-template<class T>
-inline
-bool operator < ( optional<T> const& x, T const& y )
-{ return less_pointees(x, optional<T>(y)); }
-
-template<class T>
-inline
-bool operator != ( optional<T> const& x, T const& y )
-{ return !( x == y ) ; }
-
-template<class T>
-inline
-bool operator > ( optional<T> const& x, T const& y )
-{ return y < x ; }
-
-template<class T>
-inline
-bool operator <= ( optional<T> const& x, T const& y )
-{ return !( y < x ) ; }
-
-template<class T>
-inline
-bool operator >= ( optional<T> const& x, T const& y )
-{ return !( x < y ) ; }
-
-//
-// T vs optional<T> cases
-//
-
-template<class T>
-inline
-bool operator == ( T const& x, optional<T> const& y )
-{ return equal_pointees( optional<T>(x), y ); }
-
-template<class T>
-inline
-bool operator < ( T const& x, optional<T> const& y )
-{ return less_pointees( optional<T>(x), y ); }
-
-template<class T>
-inline
-bool operator != ( T const& x, optional<T> const& y )
-{ return !( x == y ) ; }
-
-template<class T>
-inline
-bool operator > ( T const& x, optional<T> const& y )
-{ return y < x ; }
-
-template<class T>
-inline
-bool operator <= ( T const& x, optional<T> const& y )
-{ return !( y < x ) ; }
-
-template<class T>
-inline
-bool operator >= ( T const& x, optional<T> const& y )
-{ return !( x < y ) ; }
-
-
-//
-// optional<T> vs none cases
-//
-
-template<class T>
-inline
-bool operator == ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
-{ return !x; }
-
-template<class T>
-inline
-bool operator < ( optional<T> const& x, none_t )
-{ return less_pointees(x,optional<T>() ); }
-
-template<class T>
-inline
-bool operator != ( optional<T> const& x, none_t ) BOOST_NOEXCEPT
-{ return bool(x); }
-
-template<class T>
-inline
-bool operator > ( optional<T> const& x, none_t y )
-{ return y < x ; }
-
-template<class T>
-inline
-bool operator <= ( optional<T> const& x, none_t y )
-{ return !( y < x ) ; }
-
-template<class T>
-inline
-bool operator >= ( optional<T> const& x, none_t y )
-{ return !( x < y ) ; }
-
-//
-// none vs optional<T> cases
-//
-
-template<class T>
-inline
-bool operator == ( none_t , optional<T> const& y ) BOOST_NOEXCEPT
-{ return !y; }
-
-template<class T>
-inline
-bool operator < ( none_t , optional<T> const& y )
-{ return less_pointees(optional<T>() ,y); }
-
-template<class T>
-inline
-bool operator != ( none_t, optional<T> const& y ) BOOST_NOEXCEPT
-{ return bool(y); }
-
-template<class T>
-inline
-bool operator > ( none_t x, optional<T> const& y )
-{ return y < x ; }
-
-template<class T>
-inline
-bool operator <= ( none_t x, optional<T> const& y )
-{ return !( y < x ) ; }
-
-template<class T>
-inline
-bool operator >= ( none_t x, optional<T> const& y )
-{ return !( x < y ) ; }
-
-namespace optional_detail {
-
-template<bool use_default_constructor> struct swap_selector;
-
-template<>
-struct swap_selector<true>
-{
-    template<class T>
-    static void optional_swap ( optional<T>& x, optional<T>& y )
-    {
-        const bool hasX = !!x;
-        const bool hasY = !!y;
-
-        if ( !hasX && !hasY )
-            return;
-
-        if( !hasX )
-            x.emplace();
-        else if ( !hasY )
-            y.emplace();
-
-        // Boost.Utility.Swap will take care of ADL and workarounds for broken compilers
-        boost::swap(x.get(),y.get());
-
-        if( !hasX )
-            y = boost::none ;
-        else if( !hasY )
-            x = boost::none ;
-    }
-};
-
-#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-template<>
-struct swap_selector<false>
-{
-    template<class T>
-    static void optional_swap ( optional<T>& x, optional<T>& y ) 
-    //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
-    {
-        if(x)
-        {
-            if (y)
-            {
-                boost::swap(*x, *y);
-            }
-            else
-            {
-                y = boost::move(*x);
-                x = boost::none;
-            }
-        }
-        else
-        {
-            if (y)
-            {
-                x = boost::move(*y);
-                y = boost::none;
-            }
-        }
-    }
-};
-#else
-template<>
-struct swap_selector<false>
-{
-    template<class T>
-    static void optional_swap ( optional<T>& x, optional<T>& y )
-    {
-        const bool hasX = !!x;
-        const bool hasY = !!y;
-
-        if ( !hasX && hasY )
-        {
-            x = y.get();
-            y = boost::none ;
-        }
-        else if ( hasX && !hasY )
-        {
-            y = x.get();
-            x = boost::none ;
-        }
-        else if ( hasX && hasY )
-        {
-            // Boost.Utility.Swap will take care of ADL and workarounds for broken compilers
-            boost::swap(x.get(),y.get());
-        }
-    }
-};
-#endif // !defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-
-} // namespace optional_detail
-
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_CONFIG_RESTORE_OBSOLETE_SWAP_IMPLEMENTATION)
-
-template<class T>
-struct optional_swap_should_use_default_constructor : boost::false_type {} ;
-
-#else
-
-template<class T>
-struct optional_swap_should_use_default_constructor : has_nothrow_default_constructor<T> {} ;
-
-#endif //BOOST_NO_CXX11_RVALUE_REFERENCES
-
-template<class T> inline void swap ( optional<T>& x, optional<T>& y )
-  //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
-{
-    optional_detail::swap_selector<optional_swap_should_use_default_constructor<T>::value>::optional_swap(x, y);
-}
-
 } // namespace boost
 
-#endif
+#include <boost/optional/detail/optional_relops.hpp>
+#include <boost/optional/detail/optional_swap.hpp>
+
+#endif // header guard

include/boost/optional/optional_fwd.hpp

@@ -1,4 +1,5 @@
 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
+// Copyright (C) 2016 Andrzej Krzemienski
 //
 // Use, modification, and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -15,15 +16,25 @@
 #ifndef BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
 #define BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
 
+#include <boost/config.hpp>
 
 namespace boost {
 
 template<class T> class optional ;
 
-template<class T> void swap ( optional<T>& , optional<T>& );
+// This forward is needed to refer to namespace scope swap from the member swap
+template<class T> void swap ( optional<T>& , optional<T>& ) ;
 
 template<class T> struct optional_swap_should_use_default_constructor ;
 
+#ifndef BOOST_OPTIONAL_CONFIG_DONT_SPECIALIZE_OPTIONAL_REFS
+
+template<class T> class optional<T&> ;
+
+template<class T> void swap ( optional<T&>& , optional<T&>& ) BOOST_NOEXCEPT;
+
+#endif
+
 } // namespace boost
 
 #endif

meta/libraries.json

@@ -7,7 +7,7 @@
     ],
     "description": "A value-semantic, type-safe wrapper for representing 'optional' (or 'nullable') objects of a given type. An optional object may or may not contain a value of the underlying type.",
     "category": [
-        "Data structures"
+        "Data"
     ],
     "maintainers": [
         "Fernando Cacciola <fernando_cacciola -at- ciudad.com.ar>",

test/Jamfile.v2

@@ -30,6 +30,7 @@ import testing ;
     [ run optional_test_ref_convert_assign_const_int.cpp ]
     [ run optional_test_ref_portable_minimum.cpp ]
     [ run optional_test_ref_move.cpp ]
+    [ run optional_test_ref_to_val.cpp ]
     [ run optional_test_inplace_factory.cpp ]
     [ run optional_test_io.cpp ]
     [ run optional_test_move.cpp ]
@@ -39,6 +40,8 @@ import testing ;
     [ run optional_test_emplace.cpp ]
     [ run optional_test_minimum_requirements.cpp ]
     [ run optional_test_msvc_bug_workaround.cpp ]
+    [ compile optional_test_sfinae_friendly_value_ctor.cpp ]
+    [ compile-fail optional_test_ref_convert_assign_const_int_prevented.cpp ]
     [ compile-fail optional_test_fail1.cpp ]
     [ compile-fail optional_test_fail3a.cpp ]
     [ compile-fail optional_test_fail3b.cpp ]
@@ -60,5 +63,11 @@ import testing ;
     [ compile-fail optional_test_fail_io_without_io.cpp ]
     [ compile-fail optional_test_fail_none_io_without_io.cpp ]
     [ compile-fail optional_test_fail_convert_assign_of_enums.cpp ]
+    [ run optional_xconfig_NO_PROPER_ASSIGN_FROM_CONST_INT_pass.cpp ]
+    [ run-fail optional_xconfig_NO_PROPER_ASSIGN_FROM_CONST_INT_fail.cpp ]
+    [ run optional_xconfig_NO_PROPER_CONVERT_FROM_CONST_INT_pass.cpp ]
+    [ run-fail optional_xconfig_NO_PROPER_CONVERT_FROM_CONST_INT_fail.cpp ]
+    [ run optional_xconfig_NO_LEGAL_CONVERT_FROM_REF_pass.cpp ]
+    [ compile-fail optional_xconfig_NO_LEGAL_CONVERT_FROM_REF_fail.cpp ]
   ;
 }

test/optional_ref_assign_test_defs.hpp

@@ -163,26 +163,11 @@ void test_rebinding_assignment_semantics()
   BOOST_TEST_EQ(val(v), 2);
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_converting_assignment()
 {
   typename concrete_type_of<T>::type v1(1), v2(2), v3(3);
-  optional<T&> oA(v1), oB(none);
-  
-  oA = v2;
-  BOOST_TEST(oA);
-  BOOST_TEST(addressof(*oA) == addressof(v2));
-  
-  oB = v3;
-  BOOST_TEST(oB);
-  BOOST_TEST(addressof(*oB) == addressof(v3));
-}
-
-template <typename T>
-void test_converting_assignment_for_noconst_const()
-{
-  typename concrete_type_of<T>::type v1(1), v2(2), v3(3);
-  optional<const T&> oA(v1), oB(none);
+  optional<U&> oA(v1), oB(none);
   
   oA = v2;
   BOOST_TEST(oA);
@@ -194,4 +179,3 @@ void test_converting_assignment_for_noconst_const()
 }
 
 #endif //BOOST_OPTIONAL_TEST_OPTIONAL_REF_ASSIGN_TEST_DEFS_AK_07JAN2015_HPP
-

test/optional_test_emplace.cpp

@@ -24,7 +24,7 @@
 using boost::optional;
 using boost::none;
 
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
 
 class Guard
 {
@@ -90,7 +90,7 @@ void test_emplace()
 
 #endif
 
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES)
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
 
 
 struct ThrowOnMove
@@ -120,7 +120,7 @@ struct Thrower
     
 private:
     Thrower(Thrower const&);
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES)
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     Thrower(Thrower&&);
 #endif
 };
@@ -192,10 +192,10 @@ void test_emplace()
 
 int main()
 {
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
     test_emplace();
 #endif
-#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES)
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     test_no_moves_on_emplacement();
 #endif
     test_clear_on_throw();

test/optional_test_move.cpp

@@ -24,7 +24,7 @@ using boost::none;
 //#ifndef BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT
 //#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
 
-#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
 enum State
 {
@@ -334,7 +334,7 @@ void test_optional_ref_to_movables()
 
 int main()
 {
-#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     test_move_ctor_from_U();
     test_move_ctor_form_T();
     test_move_ctor_from_optional_T();

test/optional_test_noexcept_move.cpp

@@ -20,7 +20,7 @@
 using boost::optional;
 
 
-#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+#ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 #ifndef BOOST_NO_CXX11_NOEXCEPT
 
 // these 4 classes have different noexcept signatures in move operations
@@ -106,7 +106,7 @@ void test_noexcept_optional_with_operator() // compile-time test
 }
 
 #endif // !defned BOOST_NO_CXX11_NOEXCEPT
-#endif // !defined BOOST_NO_CXX11_RVALUE_REFERENCES
+#endif // !defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
 int main()
 {

test/optional_test_ref_assign_portable_minimum.cpp

@@ -38,7 +38,7 @@ void test_optional_ref_assignment()
 int main()
 {
   test_optional_ref_assignment<ScopeGuard>();
-  //test_optional_ref_assignment<Abstract>();
+  test_optional_ref_assignment<Abstract>();
   
   return boost::report_errors();
 }

test/optional_test_ref_convert_assign_const_int.cpp

@@ -23,8 +23,8 @@
 
 int main()
 {
-  test_converting_assignment<const int>();
-  test_converting_assignment_for_noconst_const<int>();
-  
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+  test_converting_assignment<const int, const int>();
+#endif
   return boost::report_errors();
 }

test/optional_test_ref_convert_assign_const_int_prevented.cpp

@@ -0,0 +1,32 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at: akrzemi1@gmail.com
+
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/addressof.hpp"
+#include "boost/core/enable_if.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "testable_classes.hpp"
+#include "optional_ref_assign_test_defs.hpp"
+
+int main()
+{
+#ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+  test_converting_assignment<const int, const int>();
+#else
+  BOOST_STATIC_ASSERT_MSG(false, "EXPECTED TEST COMPILE-TIME FAILURE");
+#endif
+  return boost::report_errors();
+}

test/optional_test_ref_convert_assign_mutable_int.cpp

@@ -23,7 +23,8 @@
 
 int main()
 {
-  test_converting_assignment<int>();
+  test_converting_assignment<int, int>();
+  test_converting_assignment<int, const int>();
   
   return boost::report_errors();
 }

test/optional_test_ref_convert_assign_non_int.cpp

@@ -25,15 +25,15 @@
 template <typename T>
 void test_all_const_cases()
 {
-  test_converting_assignment<T>();
-  test_converting_assignment<const T>();
-  test_converting_assignment_for_noconst_const<T>();
+  test_converting_assignment<T, T>();
+  test_converting_assignment<const T, const T>();
+  test_converting_assignment<T, const T>();
 }
 
 int main()
 {
   test_all_const_cases<ScopeGuard>();
-  //test_all_const_cases<Abstract>();
+  test_all_const_cases<Abstract>();
   
   return boost::report_errors();
 }

test/optional_test_ref_converting_ctor.cpp

@@ -101,7 +101,7 @@ int main()
 {
   test_all_const_cases<int>();
   test_all_const_cases<ScopeGuard>();
-  //test_all_const_cases<Abstract>();
+  test_all_const_cases<Abstract>();
   
   return boost::report_errors();
 }

test/optional_test_ref_portable_minimum.cpp

@@ -199,11 +199,11 @@ void test_direct_init_for()
   BOOST_TEST_EQ(val(v), 7);
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_clearing_the_value()
 {
   typename concrete_type_of<T>::type v(2);
-  optional<T&> o1(v), o2(v);
+  optional<U&> o1(v), o2(v);
   
   BOOST_TEST(o1);
   BOOST_TEST(o1 != none);
@@ -220,11 +220,11 @@ void test_clearing_the_value()
   BOOST_TEST_EQ(val(v), 2);
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_equality()
 {
   typename concrete_type_of<T>::type v1(1), v2(2), v2_(2), v3(3);
-  optional<T&> o1(v1), o2(v2), o2_(v2_), o3(v3), o3_(v3), oN, oN_;
+  optional<U&> o1(v1), o2(v2), o2_(v2_), o3(v3), o3_(v3), oN, oN_;
   // o2 and o2_ point to different objects; o3 and o3_ point to the same object
   
   BOOST_TEST(oN  == oN);
@@ -256,11 +256,11 @@ void test_equality()
   BOOST_TEST( (o2  != oN));
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_order()
 {
   typename concrete_type_of<T>::type v1(1), v2(2), v2_(2), v3(3);
-  optional<T&> o1(v1), o2(v2), o2_(v2_), o3(v3), o3_(v3), oN, oN_;
+  optional<U&> o1(v1), o2(v2), o2_(v2_), o3(v3), o3_(v3), oN, oN_;
   // o2 and o2_ point to different objects; o3 and o3_ point to the same object
   
   BOOST_TEST(!(oN  < oN));
@@ -399,13 +399,35 @@ void test_order()
   BOOST_TEST(!(o3_ < oN_));
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_swap()
 {
   typename concrete_type_of<T>::type v1(1), v2(2);
-  optional<T&> o1(v1), o1_(v1), o2(v2), o2_(v2), oN, oN_;
+  optional<U&> o1(v1), o1_(v1), o2(v2), o2_(v2), oN, oN_;
   
-  // swap(o1, o1); DOESN'T WORK
+  swap(o1, o1);
+  BOOST_TEST(o1);
+  BOOST_TEST(boost::addressof(*o1) == boost::addressof(v1));
+  
+  swap(oN, oN_);
+  BOOST_TEST(!oN);
+  BOOST_TEST(!oN_);
+  
+  swap(o1, oN);
+  BOOST_TEST(!o1);
+  BOOST_TEST(oN);
+  BOOST_TEST(boost::addressof(*oN) == boost::addressof(v1));
+  
+  swap(oN, o1);
+  BOOST_TEST(!oN);
+  BOOST_TEST(o1);
+  BOOST_TEST(boost::addressof(*o1) == boost::addressof(v1));
+  
+  swap(o1_, o2_);
+  BOOST_TEST(o1_);
+  BOOST_TEST(o2_);
+  BOOST_TEST(boost::addressof(*o1_) == boost::addressof(v2));
+  BOOST_TEST(boost::addressof(*o2_) == boost::addressof(v1));
 }
 
 template <typename T>
@@ -413,11 +435,11 @@ void test_optional_ref()
 {
   test_not_containing_value_for<T>();
   test_direct_init_for<T>();
-  test_clearing_the_value<T>();
+  test_clearing_the_value<T, T>();
   test_arrow<T>();
-  test_equality<T>();
-  test_order<T>();
-  test_swap<T>();
+  test_equality<T, T>();
+  test_order<T, T>();
+  test_swap<T, T>();
 }
 
 template <typename T>
@@ -426,23 +448,27 @@ void test_optional_const_ref()
   test_not_containing_value_for<const T>();
   test_direct_init_for_const<T>();
   test_direct_init_for_noconst_const<T>();
-  test_clearing_the_value<const T>();
+  test_clearing_the_value<const T, const T>();
+  test_clearing_the_value<T, const T>();
   test_arrow_const<T>();
   test_arrow_noconst_const<T>();
-  test_equality<const T>();
-  test_order<const T>();
-  //test_swap<T>();
+  test_equality<const T, const T>();
+  test_equality<T, const T>();
+  test_order<const T, const T>();
+  test_order<T, const T>();
+  test_swap<const T, const T>();
+  test_swap<T, const T>();
 }
 
 int main()
 {
   test_optional_ref<int>();
   test_optional_ref<ScopeGuard>();
-  //test_optional_ref<Abstract>();
+  test_optional_ref<Abstract>();
   
   test_optional_const_ref<int>();
   test_optional_const_ref<ScopeGuard>();
-  //test_optional_const_ref<Abstract>();
+  test_optional_const_ref<Abstract>();
   
   return boost::report_errors();
 }

test/optional_test_ref_to_val.cpp

@@ -0,0 +1,116 @@
+// Copyright (C) 2016 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/lightweight_test.hpp"
+
+using boost::optional;
+using boost::none;
+
+struct Value
+{
+  int val;
+  explicit Value(int v) : val(v) {}
+};
+
+int val(int const& i)
+{
+  return i;
+}
+
+int val(Value const& v)
+{
+  return v.val;
+}
+
+template <typename Tref>
+optional<Tref&> make_opt_ref(Tref& v)
+{
+  return optional<Tref&>(v);
+}
+
+template <typename Tval, typename Tref>
+void test_construct_from_optional_ref()
+{
+    Tref v1 (1), v2 (2);
+    
+    optional<Tref&> opt_ref0;
+    optional<Tref&> opt_ref1 (v1);
+    
+    optional<Tval> opt_val0 (opt_ref0);
+    optional<Tval> opt_val1 (opt_ref1);
+    optional<Tval> opt_val2 (make_opt_ref(v2));
+    
+    BOOST_TEST (!opt_val0);
+    BOOST_TEST (opt_val1);
+    BOOST_TEST (opt_val2);
+    
+    BOOST_TEST_EQ (1, val(*opt_val1));
+    BOOST_TEST_EQ (2, val(*opt_val2));
+    
+    BOOST_TEST (boost::addressof(*opt_val1) != boost::addressof(v1));
+    BOOST_TEST (boost::addressof(*opt_val2) != boost::addressof(v2));
+}
+
+template <typename Tval, typename Tref>
+void test_assign_from_optional_ref()
+{
+    Tref v1 (1), v2 (2);
+    
+    optional<Tref&> opt_ref0;
+    optional<Tref&> opt_ref1 (v1);
+    
+    optional<Tval> opt_val0;
+    optional<Tval> opt_val1;
+    optional<Tval> opt_val2;
+    
+    opt_val0 = opt_ref0;
+    opt_val1 = opt_ref1;
+    opt_val2 = make_opt_ref(v2);
+    
+    BOOST_TEST (!opt_val0);
+    BOOST_TEST (opt_val1);
+    BOOST_TEST (opt_val2);
+    
+    BOOST_TEST_EQ (1, val(*opt_val1));
+    BOOST_TEST_EQ (2, val(*opt_val2));
+    
+    BOOST_TEST (boost::addressof(*opt_val1) != boost::addressof(v1));
+    BOOST_TEST (boost::addressof(*opt_val2) != boost::addressof(v2));
+}
+
+
+int main()
+{
+    test_construct_from_optional_ref<int, int>();
+    test_construct_from_optional_ref<int, int const>();
+    test_construct_from_optional_ref<int const, int const>();
+    test_construct_from_optional_ref<int const, int>();
+    
+    test_construct_from_optional_ref<Value, Value>();
+    test_construct_from_optional_ref<Value, Value const>();
+    test_construct_from_optional_ref<Value const, Value const>();
+    test_construct_from_optional_ref<Value const, Value>();
+    
+    test_assign_from_optional_ref<int, int>();
+    test_assign_from_optional_ref<int, int const>();
+
+    test_assign_from_optional_ref<Value, Value>();
+    test_assign_from_optional_ref<Value, Value const>();
+
+    return boost::report_errors();
+}

test/optional_test_sfinae_friendly_value_ctor.cpp

@@ -0,0 +1,38 @@
+// Copyright (C) 2014 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+using boost::optional;
+
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT)
+
+struct X {};
+struct Y {};
+  
+struct Resource
+{
+  explicit Resource(const X&) {}
+};
+
+BOOST_STATIC_ASSERT(( boost::is_constructible<Resource, const X&>::value));
+BOOST_STATIC_ASSERT((!boost::is_constructible<Resource, const Y&>::value));
+
+BOOST_STATIC_ASSERT(( boost::is_constructible<optional<Resource>, const X&>::value));
+BOOST_STATIC_ASSERT((!boost::is_constructible<optional<Resource>, const Y&>::value));
+  
+#endif
+
+int main() { }

test/optional_test_swap.cpp

@@ -23,6 +23,11 @@
 
 #include "boost/core/lightweight_test.hpp"
 
+#if __cplusplus < 201103L
+#include <algorithm>
+#else
+#include <utility>
+#endif
 
 using boost::optional;
 using boost::none;
@@ -202,13 +207,13 @@ namespace boost {
 //
 
 template <> struct optional_swap_should_use_default_constructor<
-  optional_swap_test::class_whose_default_ctor_should_be_used> : mpl::true_ {} ;
+  optional_swap_test::class_whose_default_ctor_should_be_used> : true_type {} ;
 
 template <> struct optional_swap_should_use_default_constructor<
-  optional_swap_test::class_whose_default_ctor_should_not_be_used> : mpl::false_ {} ;
+  optional_swap_test::class_whose_default_ctor_should_not_be_used> : false_type {} ;
 
 template <class T> struct optional_swap_should_use_default_constructor<
-  optional_swap_test::template_whose_default_ctor_should_be_used<T> > : mpl::true_ {} ;
+  optional_swap_test::template_whose_default_ctor_should_be_used<T> > : true_type {} ;
 
 
 //

test/optional_test_value_access.cpp

@@ -175,7 +175,7 @@ void test_const_move()
 }
 
 
-#ifndef BOOST_NO_CXX11_REF_QUALIFIERS
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
 struct MoveOnly
 {
     explicit MoveOnly(int){}

test/optional_xconfig_HACK_TO_LIST_PREDEFINED_MACROS.cpp

@@ -0,0 +1,41 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+#include <string>
+
+int main()
+{
+#if defined(__GNUC__)
+
+  std::string emptys;
+  
+#ifdef BOOST_INTEL_CXX_VERSION
+  BOOST_TEST_EQ(emptys, "HAS INTEL INSIDE");
+#else
+  BOOST_TEST_EQ(emptys, "NO INTEL INSIDE");
+#endif
+  
+#if !defined BOOST_NO_CXX11_RVALUE_REFERENCES
+  BOOST_TEST_EQ(emptys, "HAS RVALUE REFS");
+#else
+  BOOST_TEST_EQ(emptys, "NO RVALUE REFS");
+#endif
+
+  int empty = -1;
+  BOOST_TEST_EQ(empty, __GNUC__);
+  BOOST_TEST_EQ(empty, __GNUC_MINOR__);
+  BOOST_TEST_EQ(empty, __GNUC_PATCHLEVEL__);
+  BOOST_TEST_EQ(empty, __cplusplus);
+#endif
+  return boost::report_errors();
+}

test/optional_xconfig_NO_LEGAL_CONVERT_FROM_REF_fail.cpp

@@ -0,0 +1,37 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/ignore_unused.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#if (defined BOOST_NO_CXX11_RVALUE_REFERENCES) || (!defined BOOST_OPTIONAL_CONFIG_NO_LEGAL_CONVERT_FROM_REF)
+
+static_assert(false, "failed as requested");
+
+#else
+
+struct S {};
+
+struct Binder
+{
+  S& ref_;
+  template <typename R> Binder (R&&r) : ref_(r) {}
+};
+
+int main()
+{
+  S s ;
+  Binder b = s;
+  boost::ignore_unused(b);
+}
+
+#endif

test/optional_xconfig_NO_LEGAL_CONVERT_FROM_REF_pass.cpp

@@ -0,0 +1,38 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/ignore_unused.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#if (defined BOOST_NO_CXX11_RVALUE_REFERENCES) || (defined BOOST_OPTIONAL_CONFIG_NO_LEGAL_CONVERT_FROM_REF)
+
+int main() { return 0; }
+
+#else
+
+struct S {};
+
+struct Binder
+{
+  S& ref_;
+  template <typename R> Binder (R&&r) : ref_(r) {}
+};
+
+int main()
+{
+  S s ; 
+  Binder b = s;
+  boost::ignore_unused(b);
+  return 0;
+}
+
+#endif

test/optional_xconfig_NO_PROPER_ASSIGN_FROM_CONST_INT_fail.cpp

@@ -0,0 +1,42 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+
+int main()
+{
+  BOOST_ERROR("failed as requested");
+  return boost::report_errors();
+}
+
+#else
+
+const int global_i = 0;
+
+struct Binder
+{
+  void operator=(const int& i)
+  {
+    BOOST_TEST(&i == &global_i);
+  }
+};
+
+int main()
+{
+  Binder s;
+  s = global_i;
+  return boost::report_errors();
+}
+
+#endif

test/optional_xconfig_NO_PROPER_ASSIGN_FROM_CONST_INT_pass.cpp

@@ -0,0 +1,41 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+
+const int global_i = 0;
+
+struct Binder
+{
+  void operator=(const int& i)
+  {
+    BOOST_TEST(&i == &global_i);
+  }
+};
+
+int main()
+{
+  Binder s;
+  s = global_i;
+  return boost::report_errors();
+}
+
+#else
+
+int main()
+{
+  return boost::report_errors();
+}
+
+#endif

test/optional_xconfig_NO_PROPER_CONVERT_FROM_CONST_INT_fail.cpp

@@ -0,0 +1,43 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/ignore_unused.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+
+int main()
+{
+  BOOST_ERROR("failed as requested");
+  return boost::report_errors();
+}
+
+#else
+
+const int global_i = 0;
+
+struct Binder
+{
+  Binder(const int& i)
+  {
+    BOOST_TEST(&i == &global_i);
+  }
+};
+
+int main()
+{
+  Binder b = global_i;
+  boost::ignore_unused(b);
+  return boost::report_errors();
+}
+
+#endif

test/optional_xconfig_NO_PROPER_CONVERT_FROM_CONST_INT_pass.cpp

@@ -0,0 +1,42 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/core/ignore_unused.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/optional/detail/optional_config.hpp"
+
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT
+
+const int global_i = 0;
+
+struct Binder
+{
+  Binder(const int& i)
+  {
+    BOOST_TEST(&i == &global_i);
+  }
+};
+
+int main()
+{
+  Binder b = global_i;
+  boost::ignore_unused(b);
+  return boost::report_errors();
+}
+
+#else
+
+int main()
+{
+  return boost::report_errors();
+}
+
+#endif