Remove dependency on MPL

fixed old implementation (issue #57 )
documented flat_map
2018-09-12 20:02:47 +03:00 · 2018-07-12 00:30:47 +02:00 · 2018-07-02 23:23:46 +02:00 · 2018-06-28 23:30:47 +02:00 · 2018-06-28 21:17:07 +02:00 · 2018-06-28 02:10:57 +02:00
57 changed files with 1437 additions and 322 deletions
--- a/doc/00_optional.qbk
+++ b/doc/00_optional.qbk
@ -2,7 +2,7 @@
    [quickbook 1.4]
    [authors [Cacciola Carballal, Fernando Luis]]
    [copyright 2003-2007 Fernando Luis Cacciola Carballal]
-    [copyright 2014-2017 Andrzej Krzemie&#324;ski]
+    [copyright 2014-2018 Andrzej Krzemie&#324;ski]
    [category miscellaneous]
    [id optional]
    [dirname optional]
--- a/doc/27_ref_optional_synopsis.qbk
+++ b/doc/27_ref_optional_synopsis.qbk
@ -17,16 +17,16 @@

    class in_place_init_t { /* see below */ } ; ``[link reference_in_place_init __GO_TO__]``
    const in_place_init_t in_place_init ( /* see below */ ) ;
-    
+
    class in_place_init_if_t { /*see below*/ } ; ``[link reference_in_place_init_if __GO_TO__]``
    const in_place_init_if_t in_place_init_if ( /*see below*/ ) ;
-    
+
    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__]``
@ -38,21 +38,21 @@
    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<std::decay_t<T>> make_optional ( T && v ) ; ``[link reference_make_optional_rvalue __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 optional<std::decay_t<T>> make_optional ( bool condition, T && v ) ; ``[link reference_make_optional_bool_rvalue __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_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__]``
@ -68,7 +68,7 @@
    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
@ -86,21 +86,21 @@

    class in_place_init_t { /* see below */ } ;
    const in_place_init_t in_place_init ( /* see below */ ) ;
-    
+
    class in_place_init_if_t { /*see below*/ } ;
    const in_place_init_if_t in_place_init_if ( /*see below*/ ) ;
-    
+
    }

-Classes `in_place_init_t` and `in_place_init_if_t` are empty clsses. Their purpose is to control overload resolution in the initialization of optional objects. 
-They are empty, trivially copyable classes with disabled default constructor.  
+Classes `in_place_init_t` and `in_place_init_if_t` are empty clsses. Their purpose is to control overload resolution in the initialization of optional objects.
+They are empty, trivially copyable classes with disabled default constructor.

 [endsect]

 [section:header_optional_optional_values Optional Values]

 [#reference_operator_template]
-    
+
    template <class T>
    class optional
    {
@ -112,27 +112,27 @@ They are empty, trivially copyable classes with disabled default constructor.
        typedef T &&      rval_reference_type ;
        typedef T *       pointer_type ;
        typedef T const*  pointer_const_type ;
-        
+
        optional () noexcept ; ``[link reference_optional_constructor __GO_TO__]``

        optional ( none_t ) noexcept ; ``[link reference_optional_constructor_none_t __GO_TO__]``

        optional ( T const& v ) ; ``[link reference_optional_constructor_value __GO_TO__]``
-        
+
        optional ( T&& v ) ; ``[link reference_optional_constructor_move_value __GO_TO__]``

-        optional ( bool condition, T const& v ) ; ``[link reference_optional_constructor_bool_value __GO_TO__]`` 
+        optional ( bool condition, T const& v ) ; ``[link reference_optional_constructor_bool_value __GO_TO__]``

        optional ( optional const& rhs ) ; ``[link reference_optional_constructor_optional __GO_TO__]``
-        
+
        optional ( optional&& rhs ) noexcept(``['see below]``) ; ``[link reference_optional_move_constructor_optional __GO_TO__]``

        template<class U> explicit optional ( optional<U> const& rhs ) ; ``[link reference_optional_constructor_other_optional __GO_TO__]``
-        
+
        template<class U> explicit optional ( optional<U>&& rhs ) ; ``[link reference_optional_move_constructor_other_optional __GO_TO__]``
-        
+
        template<class... Args> explicit optional ( in_place_init_t, Args&&... args ) ; ``[link reference_optional_in_place_init __GO_TO__]``
-        
+
        template<class... Args> explicit optional ( in_place_init_if_t, bool condition, Args&&... args ) ; ``[link reference_optional_in_place_init_if __GO_TO__]``

        template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; ``[link reference_optional_constructor_factory __GO_TO__]``
@ -142,17 +142,17 @@ They are empty, trivially copyable classes with disabled default constructor.
        optional& operator = ( none_t ) noexcept ; ``[link reference_optional_operator_equal_none_t __GO_TO__]``

        optional& operator = ( T const& v ) ; ``[link reference_optional_operator_equal_value __GO_TO__]``
-        
+
        optional& operator = ( T&& v ) ; ``[link reference_optional_operator_move_equal_value __GO_TO__]``

        optional& operator = ( optional const& rhs ) ; ``[link reference_optional_operator_equal_optional __GO_TO__]``
-        
+
        optional& operator = ( optional&& rhs ) noexcept(``['see below]``) ; ``[link reference_optional_operator_move_equal_optional __GO_TO__]``

        template<class U> optional& operator = ( optional<U> const& rhs ) ; ``[link reference_optional_operator_equal_other_optional __GO_TO__]``
-        
+
        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 InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; ``[link reference_optional_operator_equal_factory __GO_TO__]``
@ -168,20 +168,30 @@ They are empty, trivially copyable classes with disabled default constructor.
        T const& operator *() const& ; ``[link reference_optional_operator_asterisk __GO_TO__]``
        T&       operator *() & ; ``[link reference_optional_operator_asterisk __GO_TO__]``
        T&&      operator *() && ; ``[link reference_optional_operator_asterisk_move __GO_TO__]``
-        
+
        T const& value() const& ; ``[link reference_optional_value __GO_TO__]``
        T&       value() & ; ``[link reference_optional_value __GO_TO__]``
        T&&      value() && ; ``[link reference_optional_value_move __GO_TO__]``
-        
+
        template<class U> T value_or( U && v ) const& ; ``[link reference_optional_value_or __GO_TO__]``
        template<class U> T value_or( U && v ) && ; ``[link reference_optional_value_or_move __GO_TO__]``
-        
+
        template<class F> T value_or_eval( F f ) const& ; ``[link reference_optional_value_or_call __GO_TO__]``
        template<class F> T value_or_eval( F f ) && ; ``[link reference_optional_value_or_call_move __GO_TO__]``

+        template<class F> auto map( F f ) const& -> ``['see below]``; ``[link reference_optional_map __GO_TO__]``
+        template<class F> auto map( F f ) & -> ``['see below]``; ``[link reference_optional_map __GO_TO__]``
+        template<class F> auto map( F f ) && -> ``['see below]``; ``[link reference_optional_map_move __GO_TO__]``
+
+        template<class F> auto flat_map( F f ) const& -> ``['see below]``; ``[link reference_optional_flat_map __GO_TO__]``
+        template<class F> auto flat_map( F f ) & -> ``['see below]``; ``[link reference_optional_flat_map __GO_TO__]``
+        template<class F> auto flat_map( F f ) && -> ``['see below]``; ``[link reference_optional_flat_map_move __GO_TO__]``
+
        T const* get_ptr() const ; ``[link reference_optional_get_ptr __GO_TO__]``
        T*       get_ptr() ; ``[link reference_optional_get_ptr __GO_TO__]``

+        bool has_value() const noexcept ; ``[link reference_optional_operator_bool __GO_TO__]``
+
        explicit operator bool() const noexcept ; ``[link reference_optional_operator_bool __GO_TO__]``

        bool operator!() const noexcept ; ``[link reference_optional_operator_not __GO_TO__]``
@ -198,7 +208,7 @@ They are empty, trivially copyable classes with disabled default constructor.
        bool is_initialized() const ; ``[link reference_optional_is_initialized __GO_TO__]``

        // (deprecated)
-        T const& get_value_or( T const& default ) const ; ``[link reference_optional_get_value_or_value __GO_TO__]`` 
+        T const& get_value_or( T const& default ) const ; ``[link reference_optional_get_value_or_value __GO_TO__]``
    };


@ -225,22 +235,21 @@ They are empty, trivially copyable classes with disabled default constructor.
        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> 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__]``
@ -249,13 +258,19 @@ They are empty, trivially copyable classes with disabled default constructor.
        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__]``

+        template<class F> auto map( F f ) const -> ``['see below]``; ``[link reference_optional_ref_map __GO_TO__]``
+
+        template<class F> auto flat_map( F f ) const -> ``['see below]``; ``[link reference_optional_ref_flat_map __GO_TO__]``
+
        T* get_ptr() const noexcept ; ``[link reference_optional_ref_get_ptr __GO_TO__]``

+        bool has_value() const noexcept ; ``[link reference_optional_ref_operator_bool __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__]``
@ -272,8 +287,8 @@ They are empty, trivially copyable classes with disabled default constructor.
        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__]`` 
-        
+        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
    };
--- a/doc/28_ref_optional_semantics.qbk
+++ b/doc/28_ref_optional_semantics.qbk
@ -233,7 +233,7 @@ __SPACE__
 arguments `std::forward<Args>(args)...`.
 * [*Postconditions:] `*this` is initialized.
 * [*Throws:] Any exception thrown by the selected constructor of `T`.
-* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here]. 
+* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here].

 * [*Example:]
 ``
@ -257,7 +257,7 @@ __SPACE__
 * [*Effect:] If `condition` is `true`, initializes the contained value as if direct-non-list-initializing an object of type `T` with the arguments `std::forward<Args>(args)...`.
 * [*Postconditions:] `bool(*this) == condition`.
 * [*Throws:] Any exception thrown by the selected constructor of `T`.
-* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here]. 
+* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here].

 * [*Example:]
 ``
@ -376,13 +376,13 @@ __SPACE__
 * [*Requires:] `T` is __COPY_CONSTRUCTIBLE__ and `CopyAssignable`.
 * [*Effects:]
 [table
-  [] 
+  []
  [[][[*`*this` contains a value]][[*`*this` does not contain a value]]]
  [[[*`rhs` contains a value]][assigns `*rhs` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `*rhs`]]
  [[[*`rhs` does not contain a value]][destroys the contained value by calling `val->T::~T()`][no effect]]
 ]
 * [*Returns:] `*this`;
-* [*Postconditions:] `bool(rhs) == bool(*this)`. 
+* [*Postconditions:] `bool(rhs) == bool(*this)`.
 * [*Exception Safety:] If any exception is thrown, the initialization state of `*this` and `rhs` remains unchanged.
 If an exception is thrown during the call to `T`'s copy constructor, no effect.
 If an exception is thrown during the call to `T`'s copy assignment, the state of its contained value is as defined by the exception safety guarantee of `T`'s copy assignment.
@ -406,14 +406,14 @@ __SPACE__

 * [*Requires:] `T` is __MOVE_CONSTRUCTIBLE__ and `MoveAssignable`.
 * [*Effects:]
-[table 
+[table
  []
  [[][[*`*this` contains a value]][[*`*this` does not contain a value]]]
  [[[*`rhs` contains a value]][assigns `std::move(*rhs)` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `std::move(*rhs)`]]
  [[[*`rhs` does not contain a value]][destroys the contained value by calling `val->T::~T()`][no effect]]
 ]
 * [*Returns:] `*this`;
-* [*Postconditions:] `bool(rhs) == bool(*this)`. 
+* [*Postconditions:] `bool(rhs) == bool(*this)`.
 * [*Remarks:] The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value`.
 * [*Exception Safety:] If any exception is thrown, the initialization state of `*this` and `rhs` remains unchanged. If an exception is
 thrown during the call to `T`'s move constructor, the state of `*rhs` is determined by the exception safety guarantee
@ -437,15 +437,15 @@ __SPACE__

 [: `template<U> optional& optional<T>::operator= ( optional<U> const& rhs ) ;`]

-* [*Effect:] 
-[table 
+* [*Effect:]
+[table
  []
  [[][[*`*this` contains a value]][[*`*this` does not contain a value]]]
  [[[*`rhs` contains a value]][assigns `*rhs` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `*rhs`]]
  [[[*`rhs` does not contain a value]][destroys the contained value by calling `val->T::~T()`][no effect]]
 ]
 * [*Returns:] `*this`.
-* [*Postconditions:] `bool(rhs) == bool(*this)`. 
+* [*Postconditions:] `bool(rhs) == bool(*this)`.
 * [*Exception Safety:] If any exception is thrown, the result of the expression `bool(*this)` remains unchanged.
 If an exception is thrown during the call to `T`'s constructor, no effect.
 If an exception is thrown during the call to `T`'s assignment, the state of its contained value is as defined by the exception safety guarantee of `T`'s copy assignment.
@ -467,13 +467,13 @@ __SPACE__

 * [*Effect:]
 [table
-  [] 
+  []
  [[][[*`*this` contains a value]][[*`*this` does not contain a value]]]
  [[[*`rhs` contains a value]][assigns `std::move(*rhs)` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `std::move(*rhs)`]]
  [[[*`rhs` does not contain a value]][destroys the contained value by calling `val->T::~T()`][no effect]]
 ]
 * [*Returns:] `*this`.
-* [*Postconditions:] `bool(rhs) == bool(*this)`. 
+* [*Postconditions:] `bool(rhs) == bool(*this)`.
 * [*Exception Safety:] If any exception is thrown, the result of the expression `bool(*this)` remains unchanged.
 If an exception is thrown during the call to `T`'s constructor, no effect.
 If an exception is thrown during the call to `T`'s assignment, the state of its contained value is as defined by the exception safety guarantee of `T`'s copy assignment.
@ -485,7 +485,7 @@ optional<U> opt1;

 opt1 = std::move(opt0) ;
 assert ( opt0 );
-assert ( opt1 ) 
+assert ( opt1 )
 assert ( *opt1 == static_cast<U>(v) ) ;
 ``

@ -498,11 +498,11 @@ __SPACE__
 * [*Requires:] The compiler supports rvalue references and variadic templates.
 * [*Effect:] If `*this` is initialized calls `*this = none`.
 Then initializes in-place the contained value as if direct-initializing an object
- of type `T` with `std::forward<Args>(args)...`. 
+ of type `T` with `std::forward<Args>(args)...`.
 * [*Postconditions: ] `*this` is [_initialized].
 * [*Throws:] Whatever the selected `T`'s  constructor throws.
 * [*Exception Safety:] If an exception is thrown during the initialization of `T`, `*this` is ['uninitialized].
-* [*Notes:] `T` need not be __MOVE_CONSTRUCTIBLE__ or `MoveAssignable`. On compilers that do not suppor variadic templates or rvalue references, this function is available in limited functionality. For details [link optional_emplace_workaround see here].  
+* [*Notes:] `T` need not be __MOVE_CONSTRUCTIBLE__ or `MoveAssignable`. On compilers that do not suppor variadic templates or rvalue references, this function is available in limited functionality. For details [link optional_emplace_workaround see here].
 * [*Example:]
 ``
 T v;
@ -685,6 +685,65 @@ __SPACE__

 __SPACE__

+[#reference_optional_map]
+
+[: `template<class F> auto optional<T>::map(F f) const& -> `['see below]` ;`]
+[: `template<class F> auto optional<T>::map(F f) & -> `['see below]` ;`]
+
+* [*Effects:] `if (*this) return f(**this); else return none;`
+* [*Notes:] The return type of these overloads is `optional<decltype(f(**this))>`. On compilers that do not support ref-qualifiers on member functions, these two (as well as the next one) overloads are replaced with good old const and non-const overloads.
+* [*Example:]
+``
+auto length = [](const string& s){ return s.size(); };
+optional<string> o1 {}, o2 {"cat"};
+optional<size_t> os1 = o1.map(length), os2 = o2.map(length);
+assert ( !os1 ) ;
+assert ( os2 ) ;
+assert ( *os2 == 3 ) ;
+``
+
+__SPACE__
+
+[#reference_optional_map_move]
+
+[: `template<class F> auto optional<T>::map(F f) && -> `['see below]` ;`]
+
+* [*Effects:] `if (*this) return f(std::move(**this)); else return none;`
+* [*Notes:] The return type of this overload is `optional<decltype(f(istd::move(**this)))>`.
+
+__SPACE__
+
+[#reference_optional_flat_map]
+
+[: `template<class F> auto optional<T>::flat_map(F f) const& -> `['see below]` ;`]
+[: `template<class F> auto optional<T>::flat_map(F f) & -> `['see below]` ;`]
+
+* [*Requires:] The return type of expression `f(**this)` is `optional<U>` for some object or reference type `U`.
+* [*Effects:] `if (*this) return f(**this); else return none;`
+* [*Notes:] The return type of these overloads is `optional<U>`. On compilers that do not support ref-qualifiers on member functions, these two (as well as the next one) overloads are replaced with good old const and non-const overloads.
+* [*Example:]
+``
+optional<char> first_char(const string& s) {
+  return s.empty() ? none : optional<char>(s[0]);
+};
+optional<string> o1 {}, o2 {"cat"};
+optional<char> os1 = o1.flat_map(first_char), os2 = o2.flat_map(first_char);
+assert ( !os1 ) ;
+assert ( os2 ) ;
+assert ( *os2 == 'c' ) ;
+``
+__SPACE__
+
+[#reference_optional_flat_map_move]
+
+[: `template<class F> auto optional<T>::flat_map(F f) && -> `['see below]` ;`]
+
+* [*Requires:] The return type of expression `f(std::move(**this))` is `optional<U>` for some object or reference type `U`.
+* [*Effects:] `if (*this) return f(std::move(**this)); else return none;`
+* [*Notes:] The return type of this overload is `optional<U>`.
+
+__SPACE__
+
 [#reference_optional_get_value_or_value]

 [: `T const& optional<T>::get_value_or( T const& default) const ;`]
@ -754,6 +813,7 @@ __SPACE__
 [#reference_optional_operator_bool]

 [: `explicit optional<T>::operator bool() const noexcept ;`]
+[: `bool optional<T>::has_value() const noexcept ;`]

 * [*Returns:] `get_ptr() != 0`.
 * [*Notes:] On compilers that do not support explicit conversion operators this falls back to safe-bool idiom.
@ -815,7 +875,7 @@ __SPACE__
 [: `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]. 
+* [*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;
@ -842,7 +902,7 @@ __SPACE__
 [: `optional<T&>::optional ( optional const& rhs ) noexcept ;`]

 * [*Effects: ] Initializes `ref` with expression `rhs.ref`.
- 
+
 * [*Postconditions:] `bool(*this) == bool(rhs)`.

 * [*Example:]
@ -875,7 +935,7 @@ __SPACE__
 * [*Requires:] `is_convertible<U&, T&>::value` is `true`.

 * [*Effects: ] Initializes `ref` with expression `rhs.ref`.
- 
+
 * [*Postconditions:] `bool(*this) == bool(rhs)`.


@ -891,7 +951,7 @@ __SPACE__

 * [*Postconditions:] `bool(*this) == false`.

- 
+

 [#reference_optional_ref_copy_assign]

@ -939,7 +999,7 @@ assert ( *ora == 4 ) ;
 * [*returns:] `*this`.

 * [*Postconditions:] `bool(*this) == bool(rhs)`.
-   
+

 __SPACE__

@ -950,7 +1010,7 @@ __SPACE__
 * [*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`.
@ -1015,13 +1075,13 @@ __SPACE__

 [#reference_optional_ref_value]
 [: `T& optional<T&>::value() const ;`]
-* [*Effects:] Equivalent to `return bool(*this) ? *val : throw bad_optional_access();`. 
+* [*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;`. 
+* [*Effects:] Equivalent to `if (*this) return **this; else return r;`.
 * [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed.

 __SPACE__
@ -1033,6 +1093,21 @@ __SPACE__

 __SPACE__

+[#reference_optional_ref_map]
+[: `template<class F> auto optional<T&>::map( F f ) const -> `['see below]`;`]
+* [*Effects:] Equivalent to `if (*this) return f(**this); else return none;`.
+* [*Remarks:] The return type of this function is `optional<decltype(f(**this))>`.
+
+__SPACE__
+
+[#reference_optional_ref_flat_map]
+[: `template<class F> auto optional<T&>::flat_map( F f ) const -> `['see below]`;`]
+* [*Requires:] The return type of expression `f(**this)` is `optional<U>` for some object or reference type `U`.
+* [*Effects:] Equivalent to `if (*this) return f(**this); else return none;`.
+* [*Remarks:] The return type of this function is `optional<U>`.
+
+__SPACE__
+
 [#reference_optional_ref_get_ptr]
 [: `T* optional<T&>::get_ptr () const noexcept;`]
 * [*Returns:] `ref`.
@ -1040,6 +1115,7 @@ __SPACE__
 __SPACE__

 [#reference_optional_ref_operator_bool]
+[: `bool has_value() const noexcept;`]
 [: `optional<T&>::operator bool () const noexcept;`]
 * [*Returns:] `bool(ref)`.

@ -1074,9 +1150,9 @@ __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);`. 
+* [*Effects:] Equivalent to `return value_or(std::forward<R>(r);`.
 * [*Remarks:] This function is depprecated.
-  
+
 [endsect]


@ -1275,7 +1351,7 @@ __SPACE__

 * [*Requires:] Lvalues of type `T` shall be swappable and `T` shall be __MOVE_CONSTRUCTIBLE__.
 * [*Effects:]
-[table 
+[table
  []
  [[][[*`*this` contains a value]][[*`*this` does not contain a value]]]
  [[[*`rhs` contains a value]][calls `swap(*(*this), *rhs)`][initializes the contained value of `*this` as if direct-initializing an object of type `T` with the expression `std::move(*rhs)`, followed by `rhs.val->T::~T()`, `*this` contains a value and `rhs` does not contain a value]]
--- a/doc/91_relnotes.qbk
+++ b/doc/91_relnotes.qbk
@ -11,6 +11,13 @@

 [section:relnotes Release Notes]

+[heading Boost Release 1.68]
+
+* Added member function `has_value()` for compatibility with `std::optional` ([@https://github.com/boostorg/optional/issues/52 issue #52]).
+* Added member function `map()` for transforming `optional<T>` into `optional<U>` using a function of type `T -> U`.
+* Added member function `flat_map()` for transforming `optional<T>` into `optional<U>` using a function of type `T -> optonal<U>`.
+
+
 [heading Boost Release 1.67]

 * Fixed [@https://github.com/boostorg/optional/issues/46 issue #46].
@ -20,7 +27,7 @@
 [heading Boost Release 1.66]

 * On newer compilers `optional` is now trivially-copyable for scalar `T`s. This uses a different storage (just `T` rather than `aligned_storage`). We require the compiler to support defaulted functions.
-* Changed the implementation of `operator==` to get rid of the `-Wmaybe-uninitialized` false-positive warning from GCC. 
+* Changed the implementation of `operator==` to get rid of the `-Wmaybe-uninitialized` false-positive warning from GCC.

 [heading Boost Release 1.63]
 * Added two new in-place constructors. They work similarly to `emplace()` functions: they initialize the contained value by perfect-forwarding the obtained arguments. One constructor always initializes the contained value, the other based on a boolean condition.
@ -64,7 +71,7 @@
 * IOStream operators are now mentioned in documentation.
 * Added a way to manually disable move semantics: just define macro `BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES`. This can be used to work around [@https://svn.boost.org/trac/boost/ticket/10399 Trac #10399].
 * It is no longer possible to assign `optional<U>` to `optional<T>` when `U` is not assignable or convertible to `T` ([@https://svn.boost.org/trac/boost/ticket/11087 Trac #11087]).
-* Value accessors now work correctly on rvalues of `optional<T&>` ([@https://svn.boost.org/trac/boost/ticket/10839 Trac #10839]).  
+* Value accessors now work correctly on rvalues of `optional<T&>` ([@https://svn.boost.org/trac/boost/ticket/10839 Trac #10839]).


 [heading Boost Release 1.57]
--- a/doc/html/boost_optional/acknowledgements.html
+++ b/doc/html/boost_optional/acknowledgements.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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@ -116,8 +116,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/dependencies_and_portability.html
+++ b/doc/html/boost_optional/dependencies_and_portability.html
@ -3,7 +3,7 @@
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@ -77,8 +77,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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+++ b/doc/html/boost_optional/dependencies_and_portability/emplace_operations_in_older_compilers.html
@ -3,7 +3,7 @@
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+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -76,8 +76,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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+++ b/doc/html/boost_optional/dependencies_and_portability/optional_reference_binding.html
@ -3,7 +3,7 @@
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@ -93,8 +93,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/quick_start.html
+++ b/doc/html/boost_optional/quick_start.html
@ -3,7 +3,7 @@
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+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -155,8 +155,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/quick_start/bypassing_unnecessary_default_construction.html
+++ b/doc/html/boost_optional/quick_start/bypassing_unnecessary_default_construction.html
@ -3,7 +3,7 @@
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+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -61,8 +61,7 @@
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 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/quick_start/optional_automatic_variables.html
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@ -3,7 +3,7 @@
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@ -61,8 +61,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/quick_start/optional_data_members.html
+++ b/doc/html/boost_optional/quick_start/optional_data_members.html
@ -3,7 +3,7 @@
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@ -80,8 +80,7 @@
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 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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+++ b/doc/html/boost_optional/quick_start/storage_in_containers.html
@ -3,7 +3,7 @@
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@ -50,8 +50,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html
@ -3,7 +3,7 @@
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@ -49,8 +49,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 Andrzej Krzemie&#324;ski<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
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--- a/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html
@ -3,7 +3,7 @@
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@ -46,8 +46,7 @@
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-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 Andrzej Krzemie&#324;ski<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
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@ -3,7 +3,7 @@
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@ -33,8 +33,7 @@
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Header &lt;boost/optional/optional_fwd.hpp&gt;</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/reference.html" title="Reference">
 <link rel="prev" href="io_header/io_semantics.html" title="Detailed semantics">
@ -52,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html
@ -3,7 +3,7 @@
 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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="detailed_semantics___optional_references.html" title="Detailed Semantics - Optional References">
@ -507,8 +507,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Detailed Semantics - Optional References</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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="detailed_semantics___optional_values.html" title="Detailed Semantics - Optional Values">
@ -407,6 +407,45 @@
              is ill-formed.
            </li>
 </ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_map"></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="keyword">auto</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">map</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">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><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="identifier">f</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">none</span><span class="special">;</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> The return type of this function
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">))&gt;</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_ref_flat_map"></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="keyword">auto</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">flat_map</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">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><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> The return type of expression
+              <code class="computeroutput"><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span></code>
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>
+              for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+            </li>
+<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="identifier">f</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">none</span><span class="special">;</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Remarks:</strong></span> The return type of this function
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>.
+            </li>
+</ul></div>
 <p>
          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
        </p>
@ -422,6 +461,9 @@
          <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="keyword">bool</span> <span class="identifier">has_value</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="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>
@ -501,8 +543,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Detailed Semantics - Optional Values</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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_refs.html" title="Optional References">
@ -1471,6 +1471,126 @@
              ref-qualifiers on member functions this overload is not present.
            </li>
 </ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_map"></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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">map</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">-&gt;</span>
+            </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"> <span class="special">;</span></code>
+          </p></blockquote></div>
+<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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&amp;</span> <span class="special">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+            <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> <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="identifier">f</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">none</span><span class="special">;</span></code>
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> The return type of these overloads
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">))&gt;</span></code>.
+              On compilers that do not support ref-qualifiers on member functions,
+              these two (as well as the next one) overloads are replaced with good
+              old const and non-const overloads.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">auto</span> <span class="identifier">length</span> <span class="special">=</span> <span class="special">[](</span><span class="keyword">const</span> <span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">){</span> <span class="keyword">return</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span> <span class="special">};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">o1</span> <span class="special">{},</span> <span class="identifier">o2</span> <span class="special">{</span><span class="string">"cat"</span><span class="special">};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">size_t</span><span class="special">&gt;</span> <span class="identifier">os1</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">length</span><span class="special">),</span> <span class="identifier">os2</span> <span class="special">=</span> <span class="identifier">o2</span><span class="special">.</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">length</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">os1</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">os2</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">os2</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_map_move"></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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">map</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">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+            <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> <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="identifier">f</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="keyword">this</span><span class="special">));</span> <span class="keyword">else</span> <span class="keyword">return</span>
+              <span class="identifier">none</span><span class="special">;</span></code>
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> The return type of this overload
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">istd</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)))&gt;</span></code>.
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_flat_map"></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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">flat_map</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">-&gt;</span>
+            </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"> <span class="special">;</span></code>
+          </p></blockquote></div>
+<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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&amp;</span> <span class="special">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+            <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> The return type of expression
+              <code class="computeroutput"><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span></code>
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>
+              for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> <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="identifier">f</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">none</span><span class="special">;</span></code>
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> The return type of these overloads
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>.
+              On compilers that do not support ref-qualifiers on member functions,
+              these two (as well as the next one) overloads are replaced with good
+              old const and non-const overloads.
+            </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">char</span><span class="special">&gt;</span> <span class="identifier">first_char</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">)</span> <span class="special">{</span>
+  <span class="keyword">return</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">empty</span><span class="special">()</span> <span class="special">?</span> <span class="identifier">none</span> <span class="special">:</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span>
+<span class="special">};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">o1</span> <span class="special">{},</span> <span class="identifier">o2</span> <span class="special">{</span><span class="string">"cat"</span><span class="special">};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;</span> <span class="identifier">os1</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">first_char</span><span class="special">),</span> <span class="identifier">os2</span> <span class="special">=</span> <span class="identifier">o2</span><span class="special">.</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">first_char</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">os1</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">os2</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">os2</span> <span class="special">==</span> <span class="char">'c'</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+              <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+            </li>
+</ul></div>
+<a name="reference_optional_flat_map_move"></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="keyword">auto</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">flat_map</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">-&gt;</span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+            <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> The return type of expression
+              <code class="computeroutput"><span class="identifier">f</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="keyword">this</span><span class="special">))</span></code>
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>
+              for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effects:</strong></span> <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="identifier">f</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="keyword">this</span><span class="special">));</span> <span class="keyword">else</span> <span class="keyword">return</span>
+              <span class="identifier">none</span><span class="special">;</span></code>
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> The return type of this overload
+              is <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>.
+            </li>
+</ul></div>
 <p>
          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
        </p>
@ -1592,6 +1712,9 @@
            <span class="keyword">const</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="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">has_value</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">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
@ -1651,8 +1774,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Initialization tags</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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;">
@ -47,8 +47,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html
@ -3,7 +3,7 @@
 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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">
@ -53,7 +53,6 @@

    <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>
@ -73,8 +72,14 @@

    <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="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="keyword">auto</span> <span class="identifier">map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_map"><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="keyword">auto</span> <span class="identifier">flat_map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_flat_map"><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">bool</span> <span class="identifier">has_value</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">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>
@ -100,8 +105,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html
@ -3,7 +3,7 @@
 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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_in_place_init.html" title="Initialization tags">
@ -105,9 +105,19 @@
    <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="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="keyword">auto</span> <span class="identifier">map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map"><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="keyword">auto</span> <span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&amp;</span> <span class="special">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map"><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="keyword">auto</span> <span class="identifier">map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map_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="keyword">auto</span> <span class="identifier">flat_map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map"><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="keyword">auto</span> <span class="identifier">flat_map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&amp;</span> <span class="special">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map"><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="keyword">auto</span> <span class="identifier">flat_map</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">-&gt;</span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map_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">bool</span> <span class="identifier">has_value</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">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>
@ -130,8 +140,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/io_header.html
+++ b/doc/html/boost_optional/reference/io_header.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Header &lt;boost/optional/optional_io.hpp&gt;</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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_bad_optional_access_hpp_/detailed_semantics.html" title="Detailed semantics">
@ -58,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/reference/io_header/io_semantics.html
+++ b/doc/html/boost_optional/reference/io_header/io_semantics.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Detailed semantics</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../../index.html" title="Boost.Optional">
 <link rel="up" href="../io_header.html" title="Header &lt;boost/optional/optional_io.hpp&gt;">
 <link rel="prev" href="../io_header.html" title="Header &lt;boost/optional/optional_io.hpp&gt;">
@ -98,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/relnotes.html
+++ b/doc/html/boost_optional/relnotes.html
@ -3,7 +3,7 @@
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 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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 <link rel="prev" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
@ -28,6 +28,37 @@
 </h2></div></div></div>
 <h4>
 <a name="boost_optional.relnotes.h0"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_68"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_68">Boost
+      Release 1.68</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+          Added member function <code class="computeroutput"><span class="identifier">has_value</span><span class="special">()</span></code> for compatibility with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">optional</span></code> (<a href="https://github.com/boostorg/optional/issues/52" target="_top">issue
+          #52</a>).
+        </li>
+<li class="listitem">
+          Added member function <code class="computeroutput"><span class="identifier">map</span><span class="special">()</span></code> for transforming <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> into <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code> using a function of type <code class="computeroutput"><span class="identifier">T</span> <span class="special">-&gt;</span> <span class="identifier">U</span></code>.
+        </li>
+<li class="listitem">
+          Added member function <code class="computeroutput"><span class="identifier">flat_map</span><span class="special">()</span></code> for transforming <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> into <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code> using a function of type <code class="computeroutput"><span class="identifier">T</span> <span class="special">-&gt;</span> <span class="identifier">optonal</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code>.
+        </li>
+</ul></div>
+<h4>
+<a name="boost_optional.relnotes.h1"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_67"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_67">Boost
+      Release 1.67</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+          Fixed <a href="https://github.com/boostorg/optional/issues/46" target="_top">issue
+          #46</a>.
+        </li>
+<li class="listitem">
+          Fixed <code class="computeroutput"><span class="special">-</span><span class="identifier">Wzero</span><span class="special">-</span><span class="identifier">as</span><span class="special">-</span><span class="identifier">null</span><span class="special">-</span><span class="identifier">pointer</span><span class="special">-</span><span class="identifier">constant</span></code> warnings.
+        </li>
+</ul></div>
+<h4>
+<a name="boost_optional.relnotes.h2"></a>
      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_66"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_66">Boost
      Release 1.66</a>
    </h4>
@ -45,7 +76,7 @@
        </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_63"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_63">Boost
      Release 1.63</a>
    </h4>
@ -69,7 +100,7 @@
        </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_62"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_62">Boost
      Release 1.62</a>
    </h4>
@ -77,7 +108,7 @@
          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.h3"></a>
+<a name="boost_optional.relnotes.h5"></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>
@ -120,7 +151,7 @@
        </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_60"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_60">Boost
      Release 1.60</a>
    </h4>
@ -131,7 +162,7 @@
          #11203</a>.
        </li></ul></div>
 <h4>
-<a name="boost_optional.relnotes.h5"></a>
+<a name="boost_optional.relnotes.h7"></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>
@ -145,7 +176,7 @@
        </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h6"></a>
+<a name="boost_optional.relnotes.h8"></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>
@ -181,7 +212,7 @@
        </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h7"></a>
+<a name="boost_optional.relnotes.h9"></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>
@ -191,7 +222,7 @@
          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.h8"></a>
+<a name="boost_optional.relnotes.h10"></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>
@ -248,8 +279,7 @@
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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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/design_overview.html
+++ b/doc/html/boost_optional/tutorial/design_overview.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Design Overview</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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 <link rel="prev" href="../../optional/tutorial.html" title="Tutorial">
@ -170,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/design_overview/the_interface.html
+++ b/doc/html/boost_optional/tutorial/design_overview/the_interface.html
@ -3,7 +3,7 @@
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 <title>The Interface</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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 <link rel="prev" href="the_semantics.html" title="The semantics">
@ -173,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/design_overview/the_semantics.html
+++ b/doc/html/boost_optional/tutorial/design_overview/the_semantics.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>The semantics</title>
 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -107,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/exception_safety_guarantees.html
+++ b/doc/html/boost_optional/tutorial/exception_safety_guarantees.html
@ -3,7 +3,7 @@
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-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -161,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/gotchas.html
+++ b/doc/html/boost_optional/tutorial/gotchas.html
@ -3,7 +3,7 @@
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-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -98,8 +98,7 @@
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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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/gotchas/false_positive_with__wmaybe_uninitialized.html
+++ b/doc/html/boost_optional/tutorial/gotchas/false_positive_with__wmaybe_uninitialized.html
@ -3,7 +3,7 @@
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 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -63,8 +63,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/gotchas/mixed_relational_comparisons.html
+++ b/doc/html/boost_optional/tutorial/gotchas/mixed_relational_comparisons.html
@ -3,7 +3,7 @@
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 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -45,8 +45,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/gotchas/moved_from__optional_.html
+++ b/doc/html/boost_optional/tutorial/gotchas/moved_from__optional_.html
@ -3,7 +3,7 @@
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 <link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -49,8 +49,7 @@
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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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/in_place_factories.html
+++ b/doc/html/boost_optional/tutorial/in_place_factories.html
@ -3,7 +3,7 @@
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 <title>In-Place Factories</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">
@ -183,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>)
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--- a/doc/html/boost_optional/tutorial/io_operators.html
+++ b/doc/html/boost_optional/tutorial/io_operators.html
@ -3,7 +3,7 @@
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-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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@ -73,8 +73,7 @@
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 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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-<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/optional_references.html
+++ b/doc/html/boost_optional/tutorial/optional_references.html
@ -3,7 +3,7 @@
 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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">
@ -103,8 +103,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/optional_references/rebinding_semantics_for_assignment_of_optional_references.html
+++ b/doc/html/boost_optional/tutorial/optional_references/rebinding_semantics_for_assignment_of_optional_references.html
@ -3,7 +3,7 @@
 <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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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">
@ -133,8 +133,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/performance_considerations.html
+++ b/doc/html/boost_optional/tutorial/performance_considerations.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Performance considerations</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="type_requirements.html" title="Type requirements">
@ -56,12 +56,13 @@
 <p>
        We call it a <span class="emphasis"><em>direct</em></span> storage. This makes <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> a
        trivially-copyable type for scalar <code class="computeroutput"><span class="identifier">T</span></code>s.
-        This only works for compilers that support defaulted functions. On compilers
-        without defaulted functions we still use the direct storage, but <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> is
-        no longer recognized as trivially-copyable. Apart from scalar types, we leave
-        the programmer a way of customizing her type, so that it is reconized by
-        <code class="computeroutput"><span class="identifier">optional</span></code> as candidate for
-        optimized storage, by specializing type trait <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">opitonal_config</span><span class="special">::</span><span class="identifier">optional_uses_direct_storage_for</span></code>:
+        This only works for compilers that support defaulted functions (including
+        defaulted move assignment and constructor). On compilers without defaulted
+        functions we still use the direct storage, but <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+        is no longer recognized as trivially-copyable. Apart from scalar types, we
+        leave the programmer a way of customizing her type, so that it is reconized
+        by <code class="computeroutput"><span class="identifier">optional</span></code> as candidate
+        for optimized storage, by specializing type trait <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">opitonal_config</span><span class="special">::</span><span class="identifier">optional_uses_direct_storage_for</span></code>:
      </p>
 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="comment">// not trivial</span>
 <span class="special">{</span>
@ -250,8 +251,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/relational_operators.html
+++ b/doc/html/boost_optional/tutorial/relational_operators.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Relational operators</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="when_to_use_optional.html" title="When to use Optional">
@ -99,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/type_requirements.html
+++ b/doc/html/boost_optional/tutorial/type_requirements.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Type requirements</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="exception_safety_guarantees.html" title="Exception Safety Guarantees">
@ -95,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/boost_optional/tutorial/when_to_use_optional.html
+++ b/doc/html/boost_optional/tutorial/when_to_use_optional.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>When to use Optional</title>
 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="design_overview/the_interface.html" title="The Interface">
@ -128,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/index.html
+++ b/doc/html/index.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Boost.Optional</title>
 <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="index.html" title="Boost.Optional">
 <link rel="next" href="boost_optional/quick_start.html" title="Quick Start">
 </head>
@ -26,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski</p></div>
+<div><p class="copyright">Copyright &#169; 2014-2018 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
@ -146,7 +145,7 @@
 </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: May 17, 2017 at 23:01:39 GMT</small></p></td>
+<td align="left"><p><small>Last revised: July 02, 2018 at 21:10:01 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>
--- a/doc/html/optional/reference.html
+++ b/doc/html/optional/reference.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Reference</title>
 <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../index.html" title="Boost.Optional">
 <link rel="up" href="../index.html" title="Boost.Optional">
 <link rel="prev" href="../boost_optional/tutorial/performance_considerations.html" title="Performance considerations">
@ -75,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/optional/reference/header__boost_optional_optional_hpp_.html
+++ b/doc/html/optional/reference/header__boost_optional_optional_hpp_.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Header &lt;boost/optional/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">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <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;">
@ -97,8 +97,7 @@
 </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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/doc/html/optional/tutorial.html
+++ b/doc/html/optional/tutorial.html
@ -3,7 +3,7 @@
 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 <title>Tutorial</title>
 <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
-<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
 <link rel="home" href="../index.html" title="Boost.Optional">
 <link rel="up" href="../index.html" title="Boost.Optional">
 <link rel="prev" href="../boost_optional/quick_start/storage_in_containers.html" title="Storage in containers">
@ -139,8 +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; 2014-2017 Andrzej
-      Krzemie&#324;ski<p>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2018 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>
--- a/include/boost/optional/detail/experimental_traits.hpp
+++ b/include/boost/optional/detail/experimental_traits.hpp
@ -14,9 +14,8 @@

 #include <boost/config.hpp>
 #include <boost/detail/workaround.hpp>
+#include <boost/predef.h>
 #include <boost/type_traits.hpp>
-
-namespace boost { namespace optional_detail {
  
 // The condition to use POD implementation

@ -40,11 +39,16 @@ namespace boost { namespace optional_detail {
 # define BOOST_OPTIONAL_DETAIL_NO_SPEC_FOR_TRIVIAL_TYPES
 #endif

+// GCC 5 or higher, or clang with libc++ or clang with libstdc++ 5 or higher
 #if __cplusplus >= 201103L
 #  if BOOST_WORKAROUND(BOOST_GCC, >= 50000)
 #    define BOOST_OPTIONAL_DETAIL_USE_STD_TYPE_TRAITS
 #  elif (defined BOOST_CLANG)
-#    define BOOST_OPTIONAL_DETAIL_USE_STD_TYPE_TRAITS
+#    if BOOST_LIB_STD_CXX > 0
+#      define BOOST_OPTIONAL_DETAIL_USE_STD_TYPE_TRAITS
+#    elif BOOST_LIB_STD_GNU >= 441200023 && BOOST_LIB_STD_GNU != 450600023 && BOOST_LIB_STD_GNU != 450600026 && BOOST_LIB_STD_GNU != 460800003 && BOOST_LIB_STD_GNU != 450400026 && BOOST_LIB_STD_GNU != 460700026
+#      define BOOST_OPTIONAL_DETAIL_USE_STD_TYPE_TRAITS
+#    endif
 #  endif
 #endif  

@ -52,10 +56,12 @@ namespace boost { namespace optional_detail {
 #ifndef BOOST_OPTIONAL_DETAIL_USE_STD_TYPE_TRAITS
 #  define BOOST_OPTIONAL_DETAIL_HAS_TRIVIAL_CTOR(T) BOOST_HAS_TRIVIAL_CONSTRUCTOR(T)
 #else
+#  include <type_traits>
 #  define BOOST_OPTIONAL_DETAIL_HAS_TRIVIAL_CTOR(T) std::is_trivially_default_constructible<T>::value
 #endif
  
  
+namespace boost { namespace optional_detail {
  
 #ifndef BOOST_OPTIONAL_DETAIL_NO_SPEC_FOR_TRIVIAL_TYPES
 template <typename T>
--- a/include/boost/optional/detail/old_optional_implementation.hpp
+++ b/include/boost/optional/detail/old_optional_implementation.hpp
@ -14,10 +14,9 @@
 #define BOOST_OPTIONAL_DETAIL_OLD_OPTIONAL_IMPLEMENTATION_AJK_28JAN2015_HPP

 #include <boost/detail/reference_content.hpp>
-#include <boost/mpl/bool.hpp>
-#include <boost/mpl/if.hpp>
-#include <boost/mpl/not.hpp>
 #include <boost/type_traits/is_reference.hpp>
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/type_traits/conditional.hpp>

 namespace boost {

@ -96,13 +95,13 @@ class optional_base : public optional_tag

    typedef T value_type ;

-    typedef mpl::true_  is_reference_tag ;
-    typedef mpl::false_ is_not_reference_tag ;
+    typedef true_type  is_reference_tag ;
+    typedef false_type 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 ;
+    typedef BOOST_DEDUCED_TYPENAME conditional<is_reference_predicate::value,types_when_ref,types_when_not_ref>::type types ;

  protected:
    typedef BOOST_DEDUCED_TYPENAME types::reference_type       reference_type ;
@ -422,7 +421,7 @@ 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_STATIC_ASSERT ( !is_reference_predicate::value ) ;
       boost_optional_detail::construct<value_type>(factory, m_storage.address());
       m_initialized = true ;
     }
@ -431,7 +430,7 @@ 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 ) ;
+       BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
       factory.apply(m_storage.address()) ;
       m_initialized = true ;
     }
@ -456,7 +455,7 @@ 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_STATIC_ASSERT ( !is_reference_predicate::value ) ;
       boost_optional_detail::construct<value_type>(factory, m_storage.address());
       m_initialized = true ;
     }
@ -465,7 +464,7 @@ 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 ) ;
+       BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
       factory.apply(m_storage.address()) ;
       m_initialized = true ;
     }
--- a/include/boost/optional/detail/optional_reference_spec.hpp
+++ b/include/boost/optional/detail/optional_reference_spec.hpp
@ -1,4 +1,4 @@
-// Copyright (C) 2015-2016 Andrzej Krzemienski.
+// Copyright (C) 2015-2018 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
@ -159,6 +159,25 @@ public:
    void reset() BOOST_NOEXCEPT { ptr_ = 0; }

    bool is_initialized() const BOOST_NOEXCEPT { return ptr_ != 0; }
+    bool has_value() const BOOST_NOEXCEPT { return ptr_ != 0; }
+    
+    template <typename F>
+    optional<typename boost::result_of<F(T&)>::type> map(F f) const
+    {
+      if (this->has_value())
+        return f(this->get());
+      else
+        return none;
+    }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(T&)>::type>::type> flat_map(F f) const
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
    
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES   
 
--- a/include/boost/optional/optional.hpp
+++ b/include/boost/optional/optional.hpp
@ -1,5 +1,5 @@
 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
-// Copyright (C) 2014 - 2017 Andrzej Krzemienski.
+// Copyright (C) 2014 - 2018 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
@ -53,25 +53,41 @@
 #include <boost/move/utility.hpp>
 #include <boost/none.hpp>
 #include <boost/utility/compare_pointees.hpp>
+#include <boost/utility/result_of.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>

+namespace boost { namespace optional_detail {
+
+template <typename T>
+struct optional_value_type
+{
+};
+
+template <typename T>
+struct optional_value_type< ::boost::optional<T> >
+{
+  typedef T type;
+};
+
+}} // namespace boost::optional_detail
+
 #ifdef BOOST_OPTIONAL_CONFIG_USE_OLD_IMPLEMENTATION_OF_OPTIONAL
 #include <boost/optional/detail/old_optional_implementation.hpp>
 #else
 namespace boost {
-  
+
 namespace optional_ns {
-  
+
 // a tag for in-place initialization of contained value
 struct in_place_init_t
 {
  struct init_tag{};
  explicit in_place_init_t(init_tag){}
-};            
+};
 const in_place_init_t in_place_init ((in_place_init_t::init_tag()));

 // a tag for conditional in-place initialization of contained value
@ -81,7 +97,7 @@ struct in_place_init_if_t
  explicit in_place_init_if_t(init_tag){}
 };
 const in_place_init_if_t in_place_init_if ((in_place_init_if_t::init_tag()));
-  
+
 } // namespace optional_ns

 using optional_ns::in_place_init_t;
@ -251,7 +267,7 @@ class optional_base : public optional_tag
          construct(rhs.get_impl());
      }
    }
-    
+
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // Assigns from another optional<T> (deep-moves the rhs value)
    void assign ( optional_base&& rhs )
@ -268,7 +284,7 @@ class optional_base : public optional_tag
          construct(boost::move(rhs.get_impl()));
      }
    }
-#endif 
+#endif

    // Assigns from another _convertible_ optional<U> (deep-copies the rhs value)
    template<class U>
@ -282,7 +298,7 @@ class optional_base : public optional_tag
 #else
          assign_value( static_cast<value_type>(rhs.get()) );
 #endif
-          
+
        else destroy();
      }
      else
@ -315,7 +331,7 @@ class optional_base : public optional_tag
      }
    }
 #endif
-    
+
    // Assigns from a T (deep-copies the rhs value)
    void assign ( argument_type val )
    {
@ -323,7 +339,7 @@ class optional_base : public optional_tag
           assign_value(val);
      else construct(val);
    }
-    
+
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // Assigns from a T (deep-moves the rhs value)
    void assign ( rval_reference_type val )
@ -375,7 +391,7 @@ class optional_base : public optional_tag
    pointer_const_type get_ptr() const { return m_initialized ? get_ptr_impl() : 0 ; }
    pointer_type       get_ptr()       { return m_initialized ? get_ptr_impl() : 0 ; }

-    bool is_initialized() const { return m_initialized ; }
+    bool is_initialized() const BOOST_NOEXCEPT { return m_initialized ; }

  protected :

@ -384,7 +400,7 @@ class optional_base : public optional_tag
       ::new (m_storage.address()) value_type(val) ;
       m_initialized = true ;
     }
-     
+
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    void construct ( rval_reference_type val )
     {
@ -410,7 +426,7 @@ class optional_base : public optional_tag
      destroy();
      construct(in_place_init, boost::forward<Args>(args)...);
    }
-     
+
    template<class... Args>
    explicit optional_base ( in_place_init_t, Args&&... args )
      :
@ -418,7 +434,7 @@ class optional_base : public optional_tag
    {
      construct(in_place_init, boost::forward<Args>(args)...);
    }
-    
+
    template<class... Args>
    explicit optional_base ( in_place_init_if_t, bool cond, Args&&... args )
      :
@ -434,26 +450,26 @@ class optional_base : public optional_tag
       ::new (m_storage.address()) value_type( boost::forward<Arg>(arg) );
       m_initialized = true ;
     }
-     
+
    void construct ( in_place_init_t )
     {
       ::new (m_storage.address()) value_type();
       m_initialized = true ;
     }
-     
+
    template<class Arg>
    void emplace_assign ( Arg&& arg )
     {
       destroy();
       construct(in_place_init, boost::forward<Arg>(arg)) ;
     }
-     
+
    void emplace_assign ()
     {
       destroy();
       construct(in_place_init) ;
     }
-     
+
    template<class Arg>
    explicit optional_base ( in_place_init_t, Arg&& arg )
      :
@ -461,14 +477,14 @@ class optional_base : public optional_tag
    {
      construct(in_place_init, boost::forward<Arg>(arg));
    }
-    
+
    explicit optional_base ( in_place_init_t )
      :
      m_initialized(false)
    {
      construct(in_place_init);
    }
-    
+
    template<class Arg>
    explicit optional_base ( in_place_init_if_t, bool cond, Arg&& arg )
      :
@ -477,7 +493,7 @@ class optional_base : public optional_tag
      if ( cond )
        construct(in_place_init, boost::forward<Arg>(arg));
    }
-    
+
    explicit optional_base ( in_place_init_if_t, bool cond )
      :
      m_initialized(false)
@ -487,21 +503,21 @@ class optional_base : public optional_tag
    }

 #else
-     
+
    template<class Arg>
    void construct ( in_place_init_t, const Arg& arg )
     {
       ::new (m_storage.address()) value_type( arg );
       m_initialized = true ;
     }
-     
+
    template<class Arg>
    void construct ( in_place_init_t, Arg& arg )
     {
       ::new (m_storage.address()) value_type( arg );
       m_initialized = true ;
     }
-     
+
    void construct ( in_place_init_t )
     {
       ::new (m_storage.address()) value_type();
@ -514,20 +530,20 @@ class optional_base : public optional_tag
      destroy();
      construct(in_place_init, arg);
    }
-     
+
    template<class Arg>
    void emplace_assign ( Arg& arg )
    {
      destroy();
      construct(in_place_init, arg);
    }
-     
+
    void emplace_assign ()
    {
      destroy();
      construct(in_place_init);
    }
-    
+
    template<class Arg>
    explicit optional_base ( in_place_init_t, const Arg& arg )
      : m_initialized(false)
@ -541,13 +557,13 @@ class optional_base : public optional_tag
    {
      construct(in_place_init, arg);
    }
-    
+
    explicit optional_base ( in_place_init_t )
      : m_initialized(false)
    {
      construct(in_place_init);
    }
-    
+
    template<class Arg>
    explicit optional_base ( in_place_init_if_t, bool cond, const Arg& arg )
      : m_initialized(false)
@ -555,15 +571,15 @@ class optional_base : public optional_tag
      if ( cond )
        construct(in_place_init, arg);
    }
-    
+
    template<class Arg>
    explicit optional_base ( in_place_init_if_t, bool cond, Arg& arg )
      : m_initialized(false)
    {
      if ( cond )
        construct(in_place_init, arg);
-    } 
-    
+    }
+
    explicit optional_base ( in_place_init_if_t, bool cond )
      : m_initialized(false)
    {
@ -757,8 +773,6 @@ class optional_base : public optional_tag
    storage_type m_storage ;
 } ;

-
-
 #include <boost/optional/detail/optional_trivially_copyable_base.hpp>

 // definition of metafunciton is_optional_val_init_candidate
@ -772,7 +786,7 @@ struct is_optional_related
 {};

 #if !defined(BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT)
-  
+
 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
@ -861,7 +875,7 @@ class optional
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // 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 ( rval_reference_type val ) : base( boost::forward<T>(val) )
      {}
 #endif

@ -872,7 +886,7 @@ class optional
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    /// Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialized optional.
    // Can throw if T::T(T &&) does
-    optional ( bool cond, rval_reference_type val ) : base( cond, boost::forward<T>(val) ) 
+    optional ( bool cond, rval_reference_type val ) : base( cond, boost::forward<T>(val) )
      {}
 #endif

@ -889,11 +903,11 @@ class optional
                      )
      :
      base()
-    {      
+    {
      if ( rhs.is_initialized() )
        this->construct(rhs.get());
    }
-    
+
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // Creates a deep move of another convertible optional<U>
    // Requires a valid conversion from U to T.
@ -926,10 +940,10 @@ class optional


  template<class Expr>
-  explicit optional ( Expr&& expr, 
-                      BOOST_DEDUCED_TYPENAME boost::enable_if< optional_detail::is_optional_val_init_candidate<T, Expr>, bool>::type = true 
-  ) 
-    : base(boost::forward<Expr>(expr),boost::addressof(expr)) 
+  explicit optional ( Expr&& expr,
+                      BOOST_DEDUCED_TYPENAME boost::enable_if< optional_detail::is_optional_val_init_candidate<T, Expr>, bool>::type = true
+  )
+    : base(boost::forward<Expr>(expr),boost::addressof(expr))
    {}

 #else
@ -973,7 +987,7 @@ class optional
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES

    template<class Expr>
-    BOOST_DEDUCED_TYPENAME boost::enable_if<optional_detail::is_optional_val_init_candidate<T, Expr>, optional&>::type 
+    BOOST_DEDUCED_TYPENAME boost::enable_if<optional_detail::is_optional_val_init_candidate<T, Expr>, optional&>::type
    operator= ( Expr&& expr )
      {
        this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr));
@ -999,7 +1013,7 @@ class optional
        this->assign(rhs);
        return *this ;
      }
-      
+
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // Move-assigns from another convertible optional<U> (converts && deep-moves the rhs value)
    // Requires a valid conversion from U to T.
@ -1030,14 +1044,14 @@ class optional
 #ifndef BOOST_OPTIONAL_DETAIL_NO_DEFAULTED_MOVE_FUNCTIONS
    optional& operator= ( optional && ) = default;
 #else
-    optional& operator= ( optional && rhs ) 
+    optional& operator= ( optional && rhs )
      BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && ::boost::is_nothrow_move_assignable<T>::value)
      {
        this->assign( static_cast<base &&>(rhs) ) ;
        return *this ;
      }
-#endif      
-      
+#endif
+
 #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES

 #ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
@ -1050,7 +1064,7 @@ class optional
        this->assign( boost::forward<T_>(val) ) ;
        return *this ;
      }
-      
+
 #else

    // Assigns from a T (deep-copies the rhs value)
@ -1060,7 +1074,7 @@ class optional
        this->assign( val ) ;
        return *this ;
      }
-      
+
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    // Assigns from a T (deep-moves the rhs value)
    optional& operator= ( rval_reference_type val )
@ -1069,9 +1083,9 @@ class optional
        return *this ;
      }
 #endif
-      
+
 #endif // BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
-      
+
    // Assigns from a "none"
    // Which destroys the current value, if any, leaving this UNINITIALIZED
    // No-throw (assuming T::~T() doesn't)
@ -1080,7 +1094,7 @@ class optional
        this->assign( none_ ) ;
        return *this ;
      }
-      
+
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
    // Constructs in-place
    // upon exception *this is always uninitialized
@ -1089,29 +1103,29 @@ class optional
    {
      this->emplace_assign( boost::forward<Args>(args)... );
    }
-     
+
    template<class... Args>
    explicit optional ( in_place_init_t, Args&&... args )
    : base( in_place_init, boost::forward<Args>(args)... )
    {}
-    
+
    template<class... Args>
    explicit optional ( in_place_init_if_t, bool cond, Args&&... args )
    : base( in_place_init_if, cond, boost::forward<Args>(args)... )
    {}
-    
+
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
    template<class Arg>
    void emplace ( Arg&& arg )
     {
       this->emplace_assign( boost::forward<Arg>(arg) );
     }
-     
+
    void emplace ()
     {
       this->emplace_assign();
     }
-     
+
    template<class Args>
    explicit optional ( in_place_init_t, Args&& args )
    : base( in_place_init, boost::forward<Args>(args) )
@ -1120,12 +1134,12 @@ class optional
    explicit optional ( in_place_init_t )
    : base( in_place_init )
    {}
-    
+
    template<class Args>
    explicit optional ( in_place_init_if_t, bool cond, Args&& args )
    : base( in_place_init_if, cond, boost::forward<Args>(args) )
    {}
-    
+
    explicit optional ( in_place_init_if_t, bool cond )
    : base( in_place_init_if, cond )
    {}
@ -1135,23 +1149,23 @@ class optional
     {
       this->emplace_assign( arg );
     }
-     
+
    template<class Arg>
    void emplace ( Arg& arg )
     {
       this->emplace_assign( arg );
     }
-     
+
    void emplace ()
     {
       this->emplace_assign();
     }
-     
+
    template<class Arg>
    explicit optional ( in_place_init_t, const Arg& arg )
    : base( in_place_init, arg )
    {}
-    
+
    template<class Arg>
    explicit optional ( in_place_init_t, Arg& arg )
    : base( in_place_init, arg )
@ -1160,17 +1174,17 @@ class optional
    explicit optional ( in_place_init_t )
    : base( in_place_init )
    {}
-    
+
    template<class Arg>
    explicit optional ( in_place_init_if_t, bool cond, const Arg& arg )
    : base( in_place_init_if, cond, arg )
    {}
-    
+
    template<class Arg>
    explicit optional ( in_place_init_if_t, bool cond, Arg& arg )
    : base( in_place_init_if, cond, arg )
-    {} 
-    
+    {}
+
    explicit optional ( in_place_init_if_t, bool cond )
    : base( in_place_init_if, cond )
    {}
@ -1203,7 +1217,7 @@ class optional
    // Returns a reference to the value if this is initialized, otherwise,
    // the behaviour is UNDEFINED
    // No-throw
-#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
+#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 boost::move(this->get()) ; }
@ -1212,42 +1226,42 @@ class optional
    reference_type       operator *()       { return this->get() ; }
 #endif // !defined BOOST_NO_CXX11_REF_QUALIFIERS

-#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
    reference_const_type value() const&
-      { 
+      {
        if (this->is_initialized())
          return this->get() ;
        else
          throw_exception(bad_optional_access());
      }
-      
+
    reference_type value() &
-      { 
+      {
        if (this->is_initialized())
          return this->get() ;
        else
          throw_exception(bad_optional_access());
      }
-      
+
    reference_type_of_temporary_wrapper value() &&
-      { 
+      {
        if (this->is_initialized())
          return boost::move(this->get()) ;
        else
          throw_exception(bad_optional_access());
      }

-#else 
+#else
    reference_const_type value() const
-      { 
+      {
        if (this->is_initialized())
          return this->get() ;
        else
          throw_exception(bad_optional_access());
      }
-      
+
    reference_type value()
-      { 
+      {
        if (this->is_initialized())
          return this->get() ;
        else
@ -1259,16 +1273,16 @@ class optional
 #ifndef BOOST_NO_CXX11_REF_QUALIFIERS
    template <class U>
    value_type value_or ( U&& v ) const&
-      { 
+      {
        if (this->is_initialized())
          return get();
        else
          return boost::forward<U>(v);
      }
-    
+
    template <class U>
-    value_type value_or ( U&& v ) && 
-      { 
+    value_type value_or ( U&& v ) &&
+      {
        if (this->is_initialized())
          return boost::move(get());
        else
@ -1276,7 +1290,7 @@ class optional
      }
 #elif !defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
    template <class U>
-    value_type value_or ( U&& v ) const 
+    value_type value_or ( U&& v ) const
      {
        if (this->is_initialized())
          return get();
@ -1285,17 +1299,17 @@ class optional
      }
 #else
    template <class U>
-    value_type value_or ( U const& v ) const 
-      { 
+    value_type value_or ( U const& v ) const
+      {
        if (this->is_initialized())
          return get();
        else
          return v;
      }
-      
+
    template <class U>
-    value_type value_or ( U& v ) const 
-      { 
+    value_type value_or ( U& v ) const
+      {
        if (this->is_initialized())
          return get();
        else
@ -1304,7 +1318,7 @@ class optional
 #endif


-#ifndef BOOST_NO_CXX11_REF_QUALIFIERS
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
    template <typename F>
    value_type value_or_eval ( F f ) const&
      {
@ -1313,7 +1327,7 @@ class optional
        else
          return f();
      }
-      
+
    template <typename F>
    value_type value_or_eval ( F f ) &&
      {
@ -1322,6 +1336,61 @@ class optional
        else
          return f();
      }
+
+    template <typename F>
+    optional<typename boost::result_of<F(reference_type)>::type> map(F f) &
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename boost::result_of<F(reference_const_type)>::type> map(F f) const&
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename boost::result_of<F(reference_type_of_temporary_wrapper)>::type> map(F f) &&
+      {
+        if (this->has_value())
+          return f(boost::move(this->get()));
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(reference_type)>::type>::type> flat_map(F f) &
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(reference_const_type)>::type>::type> flat_map(F f) const&
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(reference_type_of_temporary_wrapper)>::type>::type> flat_map(F f) &&
+      {
+        if (this->has_value())
+          return f(boost::move(get()));
+        else
+          return none;
+      }
+
 #else
    template <typename F>
    value_type value_or_eval ( F f ) const
@ -1331,10 +1400,49 @@ class optional
        else
          return f();
      }
+
+    template <typename F>
+    optional<typename boost::result_of<F(reference_type)>::type> map(F f)
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename boost::result_of<F(reference_const_type)>::type> map(F f) const
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(reference_type)>::type>::type> flat_map(F f)
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
+    template <typename F>
+    optional<typename optional_detail::optional_value_type<typename boost::result_of<F(reference_const_type)>::type>::type> flat_map(F f) const
+      {
+        if (this->has_value())
+          return f(get());
+        else
+          return none;
+      }
+
 #endif
-      
+
+    bool has_value() const BOOST_NOEXCEPT { return this->is_initialized() ; }
+
    bool operator!() const BOOST_NOEXCEPT { return !this->is_initialized() ; }
-    
+
    BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
 } ;

@ -1343,7 +1451,7 @@ class optional
 #endif // BOOST_OPTIONAL_CONFIG_USE_OLD_IMPLEMENTATION_OF_OPTIONAL

 namespace boost {
-  
+
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 template<class T>
 class optional<T&&>
@ -1472,14 +1580,14 @@ get_pointer ( optional<T>& opt )
 } // 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>&
 operator<<(std::basic_ostream<CharType, CharTrait>& os, optional_detail::optional_tag const&)
 {
  BOOST_STATIC_ASSERT_MSG(sizeof(CharType) == 0, "If you want to output boost::optional, include header <boost/optional/optional_io.hpp>");
-  return os;  
+  return os;
 }

 } // namespace boost
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@ -23,6 +23,8 @@ import testing ;
    [ run optional_test_convert_from_T.cpp ]
    [ run optional_test_empty_braces.cpp ]
    [ run optional_test_make_optional.cpp ]
+    [ run optional_test_flat_map.cpp ]
+    [ run optional_test_map.cpp ]
    [ run optional_test_tie.cpp ]
    [ run optional_test_ref_assign_portable_minimum.cpp ]
    [ run optional_test_ref_assign_mutable_int.cpp ]
@ -38,6 +40,7 @@ import testing ;
    [ run optional_test_io.cpp ]
    [ run optional_test_move.cpp ]
    [ run optional_test_noexcept_move.cpp ]
+    [ run optional_test_old_impl.cpp ]
    [ run optional_test_equals_none.cpp ]
    [ run optional_test_value_access.cpp ]
    [ run optional_test_emplace.cpp ]
@ -71,6 +74,7 @@ import testing ;
    [ run optional_test_static_properties.cpp ]
    [ compile optional_test_maybe_uninitialized_warning.cpp ]
    [ compile optional_test_deleted_default_ctor.cpp ]
+    #[ run optional_xconfig_HACK_TO_LIST_PREDEFINED_MACROS.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 ]
--- a/test/optional_test.cpp
+++ b/test/optional_test.cpp
@ -32,7 +32,7 @@

 #include "boost/core/lightweight_test.hpp"

-#include "optional_test_common.cpp"
+#include "optional_test_common.hpp"

 void test_implicit_construction ( optional<double> opt, double v, double z )
 {
--- a/test/optional_test_common.hpp
+++ b/test/optional_test_common.hpp
@ -194,6 +194,9 @@ inline void check_uninitialized_const ( optional<T> const& opt )
  BOOST_TEST( !opt ) ;
  BOOST_TEST( !get_pointer(opt) ) ;
  BOOST_TEST( !opt.get_ptr() ) ;
+  BOOST_TEST( !opt.has_value() ) ;
+  BOOST_TEST( !opt.is_initialized() ) ;
+  BOOST_TEST( opt == boost::none ) ;
 }
 template<class T>
 inline void check_uninitialized ( optional<T>& opt )
@ -204,6 +207,9 @@ inline void check_uninitialized ( optional<T>& opt )
  BOOST_TEST( !opt ) ;
  BOOST_TEST( !get_pointer(opt) ) ;
  BOOST_TEST( !opt.get_ptr() ) ;
+  BOOST_TEST( !opt.has_value() ) ;
+  BOOST_TEST( !opt.is_initialized() ) ;
+  BOOST_TEST( opt == boost::none ) ;

  check_uninitialized_const(opt);
 }
@ -220,6 +226,9 @@ inline void check_initialized_const ( optional<T> const& opt )
  BOOST_TEST ( !!opt ) ;
  BOOST_TEST ( get_pointer(opt) ) ;
  BOOST_TEST ( opt.get_ptr() ) ;
+  BOOST_TEST ( opt.has_value() ) ;
+  BOOST_TEST ( opt.is_initialized() ) ;
+  BOOST_TEST ( opt != boost::none ) ;
 }

 template<class T>
@ -234,6 +243,9 @@ inline void check_initialized ( optional<T>& opt )
  BOOST_TEST ( !!opt ) ;
  BOOST_TEST ( get_pointer(opt) ) ;
  BOOST_TEST ( opt.get_ptr() ) ;
+  BOOST_TEST ( opt.has_value() ) ;
+  BOOST_TEST ( opt.is_initialized() ) ;
+  BOOST_TEST ( opt != boost::none ) ;

  check_initialized_const(opt);
 }
--- a/test/optional_test_flat_map.cpp
+++ b/test/optional_test_flat_map.cpp
@ -0,0 +1,275 @@
+// Copyright (C) 2018 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/ignore_unused.hpp"
+#include "boost/core/is_same.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/core/lightweight_test_trait.hpp"
+
+
+using boost::optional;
+using boost::make_optional;
+using boost::core::is_same;
+
+template <typename Expected, typename Deduced>
+void verify_type(Deduced)
+{
+  BOOST_TEST_TRAIT_TRUE(( is_same<Expected, Deduced> ));
+}
+
+struct Int
+{
+  int i;
+  explicit Int(int i_) : i(i_) {}
+};
+
+struct convert_t
+{
+  typedef optional<Int> result_type;
+  optional<Int> operator()(int i) { if (i != 0) return Int(i); else return boost::none; }
+};
+
+void test_flat_map_on_mutable_optional_with_function_object()
+{
+  {
+    optional<int> oi (1);
+    verify_type< optional<Int> >(oi.flat_map(convert_t()));
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(bool(oI));
+    BOOST_TEST_EQ(1, oI->i);
+  }
+  {
+    optional<int> oi (0);
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(!oI);
+  }
+  {
+    optional<int> oi;
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(!oI);
+  }
+}
+
+void test_flat_map_on_const_optional_with_function_object()
+{
+  {
+    const optional<int> oi (1);
+    verify_type< optional<Int> >(oi.flat_map(convert_t()));
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(bool(oI));
+    BOOST_TEST_EQ(1, oI->i);
+  }
+  {
+    const optional<int> oi (0);
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(!oI);
+  }
+  {
+    const optional<int> oi;
+    optional<Int> oI = oi.flat_map(convert_t());
+    BOOST_TEST(!oI);
+  }
+}
+
+void test_flat_map_with_lambda()
+{
+#if !defined BOOST_NO_CXX11_LAMBDAS && !defined BOOST_NO_CXX11_DECLTYPE_N3276
+  {
+    optional<int> oi (1);
+    verify_type< optional<Int> >(oi.flat_map([](int i){ return optional<Int>(i == 0, Int(i)); }));
+    optional<Int> oI = oi.flat_map([](int i){ return optional<Int>(i != 0, Int(i)); });
+    BOOST_TEST(bool(oI));
+    BOOST_TEST_EQ(1, oI->i);
+  }
+  {
+    optional<int> oi (0);
+    optional<Int> oI = oi.flat_map([](int i){ return optional<Int>(i != 0, Int(i)); });
+    BOOST_TEST(!oI);
+  }
+  {
+    optional<int> oi;
+    optional<Int> oI = oi.flat_map([](int i){ return optional<Int>(i != 0, Int(i)); });
+    BOOST_TEST(!oI);
+  }
+#endif // lambdas
+}
+
+struct get_opt_ref
+{
+  typedef optional<int&> result_type;
+  optional<int&> operator()(int& i) { return i != 0 ? optional<int&>(i) : optional<int&>(); }
+};
+
+void test_flat_map_obj_to_ref()
+{
+  {
+    optional<int> oi (2);
+    verify_type< optional<int&> >(oi.flat_map(get_opt_ref()));
+    optional<int&> ori = oi.flat_map(get_opt_ref());
+    BOOST_TEST(bool(ori));
+    BOOST_TEST_EQ(2, *ori);
+    *ori = 3;
+    BOOST_TEST(bool(oi));
+    BOOST_TEST_EQ(3, *oi);
+    BOOST_TEST_EQ(3, *ori);
+  }
+  {
+    optional<int> oi (0);
+    optional<int&> ori = oi.flat_map(get_opt_ref());
+    BOOST_TEST(!ori);
+  }
+  {
+    optional<int> oi;
+    optional<int&> ori = oi.flat_map(get_opt_ref());
+    BOOST_TEST(!ori);
+  }
+}
+
+optional<int&> get_opt_int_ref(Int& i)
+{
+  return i.i ? optional<int&>(i.i) : optional<int&>();
+}
+
+void test_flat_map_ref_to_ref()
+{
+  {
+    Int I (5);
+    optional<Int&> orI (I);
+    verify_type< optional<int&> >(orI.flat_map(get_opt_int_ref));
+    optional<int&> ori = orI.flat_map(get_opt_int_ref);
+    BOOST_TEST(bool(ori));
+    BOOST_TEST_EQ(5, *ori);
+    *ori = 6;
+    BOOST_TEST_EQ(6, *ori);
+    BOOST_TEST_EQ(6, I.i);
+  }
+  {
+    Int I (0);
+    optional<Int&> orI (I);
+    optional<int&> ori = orI.flat_map(get_opt_int_ref);
+    BOOST_TEST(!ori);
+  }
+  {
+    optional<Int&> orI;
+    optional<int&> ori = orI.flat_map(get_opt_int_ref);
+    BOOST_TEST(!ori);
+  }
+}
+
+optional< optional<Int> > make_opt_int(int i)
+{
+  if (i == 0)
+    return boost::none;
+  else if (i == 1)
+    return boost::make_optional(optional<Int>());
+  else
+    return boost::make_optional(boost::make_optional(Int(i)));
+}
+
+void test_flat_map_opt_opt()
+{
+  {
+    optional<int> oi (9);
+    verify_type<optional<optional<Int> > >(oi.flat_map(make_opt_int));
+    optional<optional<Int> > ooI = oi.flat_map(make_opt_int);
+    BOOST_TEST(bool(ooI));
+    BOOST_TEST(bool(*ooI));
+    BOOST_TEST_EQ(9, (**ooI).i);
+  }
+  {
+    optional<int> oi (1);
+    optional<optional<Int> > ooI = oi.flat_map(make_opt_int);
+    BOOST_TEST(bool(ooI));
+    BOOST_TEST(!*ooI);
+  }
+  {
+    optional<int> oi (0);
+    optional<optional<Int> > ooI = oi.flat_map(make_opt_int);
+    BOOST_TEST(!ooI);
+  }
+  {
+    optional<int> oi;
+    optional<optional<Int> > ooI = oi.flat_map(make_opt_int);
+    BOOST_TEST(!ooI);
+  }
+}
+
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
+struct MoveOnly
+{
+  int value;
+  explicit MoveOnly(int i) : value(i) {}
+  MoveOnly(MoveOnly && r) : value(r.value) { r.value = 0; }
+  MoveOnly& operator=(MoveOnly && r) { value = r.value; r.value = 0; return *this; }
+
+private:
+  MoveOnly(MoveOnly const&);
+  void operator=(MoveOnly const&);
+};
+
+MoveOnly makeMoveOnly(int i)
+{
+  return MoveOnly(i);
+}
+
+optional<MoveOnly> makeOptMoveOnly(int i)
+{
+  return optional<MoveOnly>(MoveOnly(i));
+}
+
+optional<int> get_val(MoveOnly m)
+{
+  return optional<int>(m.value != 0, m.value);
+}
+
+void test_flat_map_move_only()
+{
+  {
+    optional<MoveOnly> om (makeMoveOnly(1)), om2 (makeMoveOnly(2));
+    verify_type<optional<int> >(boost::move(om).flat_map(get_val));
+    optional<int> oi = boost::move(om2).flat_map(get_val);
+    BOOST_TEST(bool(oi));
+    BOOST_TEST_EQ(2, *oi);
+  }
+  {
+    optional<int> oj = makeOptMoveOnly(4).flat_map(get_val);
+    BOOST_TEST(bool(oj));
+    BOOST_TEST_EQ(4, *oj);
+  }
+  {
+    optional<int> oj = optional<MoveOnly>().flat_map(get_val);
+    BOOST_TEST(!oj);
+  }
+}
+
+#endif // no rvalue refs
+
+int main()
+{
+  test_flat_map_on_mutable_optional_with_function_object();
+  test_flat_map_on_const_optional_with_function_object();
+  test_flat_map_with_lambda();
+  test_flat_map_obj_to_ref();
+  test_flat_map_ref_to_ref();
+  test_flat_map_opt_opt();
+
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
+  test_flat_map_move_only();
+#endif
+
+  return boost::report_errors();
+}
--- a/test/optional_test_map.cpp
+++ b/test/optional_test_map.cpp
@ -0,0 +1,192 @@
+// Copyright (C) 2018 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/ignore_unused.hpp"
+#include "boost/core/is_same.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "boost/core/lightweight_test_trait.hpp"
+
+
+using boost::optional;
+using boost::make_optional;
+using boost::core::is_same;
+
+template <typename Expected, typename Deduced>
+void verify_type(Deduced)
+{
+  BOOST_TEST_TRAIT_TRUE(( is_same<Expected, Deduced> ));
+}
+  
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
+struct MoveOnly
+{
+  int value;
+  explicit MoveOnly(int i) : value(i) {}
+  MoveOnly(MoveOnly && r) : value(r.value) { r.value = 0; }
+  MoveOnly& operator=(MoveOnly && r) { value = r.value; r.value = 0; return *this; }
+  
+private:
+  MoveOnly(MoveOnly const&);
+  void operator=(MoveOnly const&);
+};
+
+MoveOnly makeMoveOnly(int i)
+{
+  return MoveOnly(i);
+}
+
+optional<MoveOnly> makeOptMoveOnly(int i)
+{
+  return optional<MoveOnly>(MoveOnly(i));
+}
+
+int get_val(MoveOnly m)
+{
+  return m.value;
+}
+
+void test_map_move_only()
+{
+  optional<MoveOnly> om (makeMoveOnly(7)), om2 (makeMoveOnly(8));
+  verify_type<optional<int> >(boost::move(om).map(get_val));
+  optional<int> oi = boost::move(om2).map(get_val);
+  BOOST_TEST(bool(oi));
+  BOOST_TEST_EQ(8, *oi);
+
+  optional<int> oj = makeOptMoveOnly(4).map(get_val);
+  BOOST_TEST(bool(oj));
+  BOOST_TEST_EQ(4, *oj);
+  
+  optional<MoveOnly> o_;
+  optional<int> oi_ = boost::move(o_).map(get_val);
+  BOOST_TEST(!oi_);
+}
+
+#endif // no rvalue refs
+
+struct Int
+{
+  int i;
+  explicit Int(int i_) : i(i_) {}
+};
+
+struct convert_t
+{
+  typedef Int result_type;
+  Int operator()(int i) { return Int(i); }
+};
+
+int& get_int_ref(Int& i)
+{
+  return i.i;
+}
+
+struct get_ref
+{
+  typedef int& result_type;
+  int& operator()(int& i) { return i; }
+};
+
+void test_map()
+{
+  optional<int> oi (1);
+  verify_type<optional<Int> >(oi.map(convert_t()));
+  optional<Int> oI = oi.map(convert_t());
+  BOOST_TEST(bool(oI));
+  BOOST_TEST_EQ(1, oI->i);
+
+  optional<Int> o_ = optional<int>().map(convert_t());
+  BOOST_TEST(!o_);
+}
+
+optional<Int> make_opt_int(int i)
+{
+  if (i != 0)
+    return Int(i);
+  else
+    return boost::none;
+}
+
+void test_map_optional()
+{
+  optional<int> o9 (9), o0 (0), o_;
+  verify_type<optional<optional<Int> > >(o9.map(make_opt_int));
+  optional<optional<Int> > oo9 = o9.map(make_opt_int);
+  BOOST_TEST(bool(oo9));  
+  BOOST_TEST(bool(*oo9));  
+  BOOST_TEST_EQ(9, (**oo9).i);
+
+  optional<optional<Int> > oo0 = o0.map(make_opt_int);
+  BOOST_TEST(bool(oo0));  
+  BOOST_TEST(!*oo0);  
+  
+  optional<optional<Int> > oo_ = o_.map(make_opt_int);
+  BOOST_TEST(!oo_);  
+}
+
+void test_map_with_lambda()
+{
+#if !defined BOOST_NO_CXX11_LAMBDAS && !defined BOOST_NO_CXX11_DECLTYPE_N3276
+  optional<int> oi (1), oj(2);
+  verify_type<optional<bool> >(oi.map([](int i){ return i == 1; }));
+  optional<bool> ob = oi.map([](int i){ return i == 1; });
+  optional<bool> oc = oj.map([](int i){ return i == 1; });
+  BOOST_TEST(bool(ob));
+  BOOST_TEST_EQ(true, *ob);
+  BOOST_TEST(bool(oc));
+  BOOST_TEST_EQ(false, *oc);
+#endif // lambdas
+}
+
+void test_map_to_ref()
+{
+  optional<int> oi (2);
+  verify_type<optional<int&> >(oi.map(get_ref()));
+  optional<int&> ori = oi.map(get_ref());
+  BOOST_TEST(bool(ori));
+  *ori = 3;
+  BOOST_TEST(bool(oi));
+  BOOST_TEST_EQ(3, *oi);
+  BOOST_TEST_EQ(3, *ori);
+}
+
+void test_map_optional_ref()
+{
+  Int I (5);
+  optional<Int&> ori (I);
+  verify_type<optional<int&> >(ori.map(get_int_ref));
+  optional<int&> orii = ori.map(get_int_ref);
+  BOOST_TEST(bool(orii));
+  BOOST_TEST_EQ(5, *orii);
+  *orii = 6;
+  BOOST_TEST_EQ(6, I.i);
+}
+
+int main()
+{
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
+  test_map_move_only();
+#endif
+  test_map_with_lambda();
+	test_map();
+  test_map_optional();
+  test_map_to_ref();
+  test_map_optional();
+  test_map_optional_ref();
+
+  return boost::report_errors();
+}
--- a/test/optional_test_old_impl.cpp
+++ b/test/optional_test_old_impl.cpp
@ -0,0 +1,223 @@
+// Copyright (C) 2014 - 2018 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
+
+#define BOOST_OPTIONAL_CONFIG_USE_OLD_IMPLEMENTATION_OF_OPTIONAL // does old implementation still work for basic usage?
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/ignore_unused.hpp"
+#include "boost/core/lightweight_test.hpp"
+
+using boost::optional;
+
+struct IntWrapper
+{
+  int _i;
+  IntWrapper(int i) : _i(i) {}
+  bool operator==(IntWrapper const& rhs) const { return _i == rhs._i; }
+};
+
+template <typename T>
+void test_function_value_or_for()
+{
+  optional<T> oM0;
+  const optional<T> oC0;
+  optional<T> oM1(1);
+  const optional<T> oC2(2);
+  
+  BOOST_TEST(oM0.value_or(5) == 5);
+  BOOST_TEST(oC0.value_or(5) == 5);
+  BOOST_TEST(oM1.value_or(5) == 1);
+  BOOST_TEST(oC2.value_or(5) == 2);
+}
+
+template <typename T>
+void test_function_value_for()
+{
+  optional<T> o0;
+  optional<T> o1(1);
+  const optional<T> oC(2);
+  
+  try
+  {
+    T& v = o1.value();
+    BOOST_TEST(v == 1);
+  }
+  catch(...)
+  {
+    BOOST_TEST(false);
+  }
+  
+  try
+  {
+    T const& v = oC.value();
+    BOOST_TEST(v == 2);
+  }
+  catch(...)
+  {
+    BOOST_TEST(false);
+  }
+  
+  BOOST_TEST_THROWS(o0.value(), boost::bad_optional_access);
+}
+
+void test_function_value()
+{
+    test_function_value_for<int>();
+    test_function_value_for<double>();
+    test_function_value_for<IntWrapper>();
+}
+
+struct FatToIntConverter
+{
+  static int conversions;
+  int _val;
+  FatToIntConverter(int val) : _val(val) {}
+  operator int() const { conversions += 1; return _val; }
+};
+
+int FatToIntConverter::conversions = 0;
+
+void test_function_value_or()
+{
+    test_function_value_or_for<int>();
+    test_function_value_or_for<double>();
+    test_function_value_or_for<IntWrapper>();
+    
+    optional<int> oi(1);
+    BOOST_TEST(oi.value_or(FatToIntConverter(2)) == 1);
+    BOOST_TEST(FatToIntConverter::conversions == 0);
+    
+    oi = boost::none;
+    BOOST_TEST(oi.value_or(FatToIntConverter(2)) == 2);
+    BOOST_TEST(FatToIntConverter::conversions == 1);
+}
+
+
+struct FunM
+{
+    int operator()() { return 5; }
+};
+
+struct FunC
+{
+    int operator()() const { return 6; }
+};
+
+int funP ()
+{
+    return 7;
+}
+
+int throw_()
+{
+    throw int();
+}
+
+void test_function_value_or_eval()
+{
+    optional<int> o1 = 1;
+    optional<int> oN;
+    FunM funM;
+    FunC funC;
+    
+    BOOST_TEST_EQ(o1.value_or_eval(funM), 1);
+    BOOST_TEST_EQ(oN.value_or_eval(funM), 5);
+    BOOST_TEST_EQ(o1.value_or_eval(FunM()), 1);
+    BOOST_TEST_EQ(oN.value_or_eval(FunM()), 5);
+    
+    BOOST_TEST_EQ(o1.value_or_eval(funC), 1);
+    BOOST_TEST_EQ(oN.value_or_eval(funC), 6);
+    BOOST_TEST_EQ(o1.value_or_eval(FunC()), 1);
+    BOOST_TEST_EQ(oN.value_or_eval(FunC()), 6);
+    
+    BOOST_TEST_EQ(o1.value_or_eval(funP), 1);
+    BOOST_TEST_EQ(oN.value_or_eval(funP), 7);
+    
+#ifndef BOOST_NO_CXX11_LAMBDAS
+    BOOST_TEST_EQ(o1.value_or_eval([](){return 8;}), 1);
+    BOOST_TEST_EQ(oN.value_or_eval([](){return 8;}), 8);
+#endif
+
+    try
+    {
+      BOOST_TEST_EQ(o1.value_or_eval(throw_), 1);
+    }
+    catch(...)
+    {
+      BOOST_TEST(false);
+    }
+    
+    BOOST_TEST_THROWS(oN.value_or_eval(throw_), int);
+}
+
+const optional<std::string> makeConstOptVal()
+{
+    return std::string("something");
+}
+
+void test_const_move()
+{
+    std::string s5 = *makeConstOptVal();
+    std::string s6 = makeConstOptVal().value();
+    boost::ignore_unused(s5);
+    boost::ignore_unused(s6);
+}
+
+
+#if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
+struct MoveOnly
+{
+    explicit MoveOnly(int){}
+    MoveOnly(MoveOnly &&){}
+    void operator=(MoveOnly &&);
+private:
+    MoveOnly(MoveOnly const&);
+    void operator=(MoveOnly const&);
+};
+
+optional<MoveOnly> makeMoveOnly()
+{
+    return MoveOnly(1);
+}
+
+MoveOnly moveOnlyDefault()
+{
+    return MoveOnly(1);
+}
+
+// compile-time test
+void test_move_only_getters()
+{
+    MoveOnly m1 = *makeMoveOnly();
+    MoveOnly m2 = makeMoveOnly().value();
+    MoveOnly m3 = makeMoveOnly().value_or(MoveOnly(1));
+    MoveOnly m4 = makeMoveOnly().value_or_eval(moveOnlyDefault);
+    boost::ignore_unused(m1);
+    boost::ignore_unused(m2);
+    boost::ignore_unused(m3);
+    boost::ignore_unused(m4);
+}
+
+#endif // !defined BOOST_NO_CXX11_REF_QUALIFIERS
+
+int main()
+{
+  test_function_value();
+  test_function_value_or();
+  test_function_value_or_eval();
+  test_const_move();
+
+  return boost::report_errors();
+}
--- a/test/optional_xconfig_HACK_TO_LIST_PREDEFINED_MACROS.cpp
+++ b/test/optional_xconfig_HACK_TO_LIST_PREDEFINED_MACROS.cpp
@ -1,4 +1,4 @@
-// Copyright (C) 2015 Andrzej Krzemienski.
+// Copyright (C) 2015 - 2018 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
@ -11,6 +11,7 @@

 #include "boost/core/lightweight_test.hpp"
 #include "boost/optional/detail/optional_config.hpp"
+#include "boost/predef.h"
 #include <string>

 int main()
@ -37,5 +38,13 @@ int main()
  BOOST_TEST_EQ(empty, __GNUC_PATCHLEVEL__);
  BOOST_TEST_EQ(empty, __cplusplus);
 #endif
+
+  BOOST_TEST_EQ(empty, BOOST_COMP_GNUC);
+  BOOST_TEST_EQ(empty, BOOST_COMP_CLANG);
+  BOOST_TEST_EQ(empty, BOOST_LANG_STDCPP);
+  BOOST_TEST_EQ(empty, BOOST_LIB_C_GNU);
+  BOOST_TEST_EQ(empty, BOOST_LIB_STD_GNU);
+  BOOST_TEST_EQ(empty, BOOST_LIB_STD_CXX);
+
  return boost::report_errors();
 }
Author	SHA1	Message	Date
Peter Dimov	c52280bb78	Remove dependency on MPL	2018-09-12 20:02:47 +03:00
Andrzej Krzemienski	228b20df82	fixed old implementation (issue #57 )	2018-07-12 00:30:47 +02:00
Andrzej Krzemienski	d0b87d2f35	documented flat_map	2018-07-02 23:23:46 +02:00
Andrzej Krzemienski	71d797b9ee	added implementation and tests of flat_map()	2018-06-28 23:30:47 +02:00
Andrzej Krzemienski	701afd43a4	fixed strange verisons of libstdc++	2018-06-28 21:17:07 +02:00
Andrzej Krzemienski	d13623884a	hopefully fixed the libstdc++ 4.9 problem (thanks Jonathan)	2018-06-28 02:10:57 +02:00
Andrzej Krzemienski	7320dd54e8	one more test hack macro to check	2018-06-27 22:23:57 +02:00
Andrzej Krzemienski	51a46f95c6	testing clang v.	2018-06-26 00:04:33 +02:00
Andrzej Krzemienski	35ca7c1ff1	added a hack test to check compiler setup	2018-06-25 23:59:19 +02:00
Andrzej Krzemienski	0169460194	fixed tests and maybe std::is_trivially_default_constructible	2018-06-25 22:50:00 +02:00
Andrzej Krzemienski	42445e94aa	Fix for C++03 tests for .map() using result_of	2018-06-24 17:12:38 +02:00
Andrzej Krzemienski	250806d029	fixed >> int C++03 templates	2018-06-24 15:22:56 +02:00
Andrzej Krzemienski	51d1bc843d	test and doc update for .map()	2018-06-23 20:53:16 +02:00
Andrzej Krzemienski	e47a017009	added o.map()	2018-06-23 18:27:14 +02:00
Andrzej Krzemienski	5182f7f30f	Added has_value()	2018-03-24 00:04:15 +01:00