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Made iterator operators conditionally defined depending on its category.

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This makes iterators defined using iterator_facade more friendly to type inspection and fixes its use with next()/prior() since commit 651a869d4f.
The arithmetic, indexing and relational operators are only defined if the iterator category or traversal permits that. Note that the implementation requires partial template specialization support now.
This commit is contained in:
Andrey Semashev
2014-06-30 00:05:38 +04:00
parent fd94cc7d78
commit 7fa65a4278
1 changed files with 292 additions and 148 deletions
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440
include/boost/iterator/iterator_facade.hpp
View File

@ -7,9 +7,11 @@
#ifndef BOOST_ITERATOR_FACADE_23022003THW_HPP
#define BOOST_ITERATOR_FACADE_23022003THW_HPP
#include <boost/config.hpp>
#include <boost/iterator.hpp>
#include <boost/iterator/interoperable.hpp>
#include <boost/iterator/iterator_traits.hpp>
#include <boost/iterator/iterator_categories.hpp>
#include <boost/iterator/detail/facade_iterator_category.hpp>
#include <boost/iterator/detail/enable_if.hpp>
@ -56,6 +58,12 @@ namespace boost
};
};
// The type trait checks if the category or traversal is at least as advanced as the specified required traversal
template< typename CategoryOrTraversal, typename Required >
struct is_traversal_at_least :
public boost::is_convertible< typename iterator_category_to_traversal< CategoryOrTraversal >::type, Required >
{};
//
// enable if for use in operator implementation.
//
@ -64,13 +72,29 @@ namespace boost
, class Facade2
, class Return
>
struct enable_if_interoperable
: ::boost::iterators::enable_if<
mpl::or_<
is_convertible<Facade1, Facade2>
, is_convertible<Facade2, Facade1>
>
, Return
struct enable_if_interoperable :
public boost::iterators::enable_if<
is_interoperable< Facade1, Facade2 >
, Return
>
{};
//
// enable if for use in implementation of operators specific for random access traversal.
//
template <
class Facade1
, class Facade2
, class Return
>
struct enable_if_interoperable_and_random_access_traversal :
public boost::iterators::enable_if<
mpl::and_<
is_interoperable< Facade1, Facade2 >
, is_traversal_at_least< typename iterator_category< Facade1 >::type, random_access_traversal_tag >
, is_traversal_at_least< typename iterator_category< Facade2 >::type, random_access_traversal_tag >
>
, Return
>
{};
@ -81,7 +105,7 @@ namespace boost
template <
class ValueParam
, class CategoryOrTraversal
, class Reference
, class Reference
, class Difference
>
struct iterator_facade_types
@ -89,16 +113,16 @@ namespace boost
typedef typename facade_iterator_category<
CategoryOrTraversal, ValueParam, Reference
>::type iterator_category;
typedef typename remove_const<ValueParam>::type value_type;
// Not the real associated pointer type
typedef typename mpl::eval_if<
boost::detail::iterator_writability_disabled<ValueParam,Reference>
, add_pointer<const value_type>
, add_pointer<value_type>
>::type pointer;
# if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) \
&& (BOOST_WORKAROUND(_STLPORT_VERSION, BOOST_TESTED_AT(0x452)) \
|| BOOST_WORKAROUND(BOOST_DINKUMWARE_STDLIB, BOOST_TESTED_AT(310))) \
@ -144,7 +168,7 @@ namespace boost
private:
mutable value_type stored_value;
};
//
// In general, we can't determine that such an iterator isn't
// writable -- we also need to store a copy of the old iterator so
@ -196,7 +220,7 @@ namespace boost
{
return stored_iterator;
}
private:
mutable value_type stored_value;
Iterator stored_iterator;
@ -208,7 +232,7 @@ namespace boost
struct is_non_proxy_reference_impl
{
static Reference r;
template <class R>
static typename mpl::if_<
is_convertible<
@ -218,17 +242,17 @@ namespace boost
, char[1]
, char[2]
>::type& helper(R const&);
BOOST_STATIC_CONSTANT(bool, value = sizeof(helper(r)) == 1);
};
template <class Reference, class Value>
struct is_non_proxy_reference
: mpl::bool_<
is_non_proxy_reference_impl<Reference, Value>::value
>
{};
# else
# else
template <class Reference, class Value>
struct is_non_proxy_reference
: is_convertible<
@ -237,8 +261,8 @@ namespace boost
, Value const volatile*
>
{};
# endif
# endif
// A metafunction to choose the result type of postfix ++
//
// Because the C++98 input iterator requirements say that *r++ has
@ -260,7 +284,7 @@ namespace boost
mpl::and_<
// A proxy is only needed for readable iterators
is_convertible<Reference,Value const&>
// No multipass iterator can have values that disappear
// before positions can be re-visited
, mpl::not_<
@ -356,7 +380,7 @@ namespace boost
>
>
{};
template <class Iterator, class Value, class Reference>
struct operator_brackets_result
{
@ -392,16 +416,28 @@ namespace boost
, iterator_difference<I1>
, iterator_difference<I2>
>
# endif
# endif
{};
};
template <
class Derived
, class Value
, class CategoryOrTraversal
, class Reference
, class Difference
, bool IsBidirectionalTraversal
, bool IsRandomAccessTraversal
>
class iterator_facade_base;
} // namespace detail
// Macros which describe the declarations of binary operators
# ifdef BOOST_NO_STRICT_ITERATOR_INTEROPERABILITY
# define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type) \
# define BOOST_ITERATOR_FACADE_INTEROP_HEAD_IMPL(prefix, op, result_type, enabler) \
template < \
class Derived1, class V1, class TC1, class Reference1, class Difference1 \
, class Derived2, class V2, class TC2, class Reference2, class Difference2 \
@ -410,24 +446,33 @@ namespace boost
operator op( \
iterator_facade<Derived1, V1, TC1, Reference1, Difference1> const& lhs \
, iterator_facade<Derived2, V2, TC2, Reference2, Difference2> const& rhs)
# else
# define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type) \
# else
# define BOOST_ITERATOR_FACADE_INTEROP_HEAD_IMPL(prefix, op, result_type, enabler) \
template < \
class Derived1, class V1, class TC1, class Reference1, class Difference1 \
, class Derived2, class V2, class TC2, class Reference2, class Difference2 \
> \
prefix typename boost::detail::enable_if_interoperable< \
prefix typename enabler< \
Derived1, Derived2 \
, typename mpl::apply2<result_type,Derived1,Derived2>::type \
>::type \
operator op( \
iterator_facade<Derived1, V1, TC1, Reference1, Difference1> const& lhs \
, iterator_facade<Derived2, V2, TC2, Reference2, Difference2> const& rhs)
# endif
# endif
# define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type) \
BOOST_ITERATOR_FACADE_INTEROP_HEAD_IMPL(prefix, op, result_type, boost::detail::enable_if_interoperable)
# define BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS_HEAD(prefix, op, result_type) \
BOOST_ITERATOR_FACADE_INTEROP_HEAD_IMPL(prefix, op, result_type, boost::detail::enable_if_interoperable_and_random_access_traversal)
# define BOOST_ITERATOR_FACADE_PLUS_HEAD(prefix,args) \
template <class Derived, class V, class TC, class R, class D> \
prefix Derived operator+ args
prefix typename boost::iterators::enable_if< \
boost::detail::is_traversal_at_least< TC, boost::random_access_traversal_tag >, \
Derived \
>::type operator+ args
//
// Helper class for granting access to the iterator core interface.
@ -440,13 +485,15 @@ namespace boost
//
class iterator_core_access
{
# if defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
# if defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
// Tasteless as this may seem, making all members public allows member templates
// to work in the absence of member template friends.
public:
# else
template <class I, class V, class TC, class R, class D> friend class iterator_facade;
template <class I, class V, class TC, class R, class D, bool IsBidirectionalTraversal, bool IsRandomAccessTraversal>
friend class detail::iterator_facade_base;
# define BOOST_ITERATOR_FACADE_RELATION(op) \
BOOST_ITERATOR_FACADE_INTEROP_HEAD(friend,op, boost::detail::always_bool2);
@ -454,27 +501,33 @@ namespace boost
BOOST_ITERATOR_FACADE_RELATION(==)
BOOST_ITERATOR_FACADE_RELATION(!=)
BOOST_ITERATOR_FACADE_RELATION(<)
BOOST_ITERATOR_FACADE_RELATION(>)
BOOST_ITERATOR_FACADE_RELATION(<=)
BOOST_ITERATOR_FACADE_RELATION(>=)
# undef BOOST_ITERATOR_FACADE_RELATION
BOOST_ITERATOR_FACADE_INTEROP_HEAD(
# define BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(op) \
BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS_HEAD(friend,op, boost::detail::always_bool2);
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(<)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(>)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(<=)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(>=)
# undef BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION
BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS_HEAD(
friend, -, boost::detail::choose_difference_type)
;
BOOST_ITERATOR_FACADE_PLUS_HEAD(
friend inline
, (iterator_facade<Derived, V, TC, R, D> const&
, typename Derived::difference_type)
, (iterator_facade<Derived, V, TC, R, D> const&
, typename Derived::difference_type)
)
;
BOOST_ITERATOR_FACADE_PLUS_HEAD(
friend inline
, (typename Derived::difference_type
, iterator_facade<Derived, V, TC, R, D> const&)
, iterator_facade<Derived, V, TC, R, D> const&)
)
;
@ -545,11 +598,156 @@ namespace boost
return *static_cast<I const*>(&facade);
}
private:
// objects of this class are useless
iterator_core_access(); //undefined
BOOST_DELETED_FUNCTION(iterator_core_access())
};
namespace detail {
// Implementation for forward traversal iterators
template <
class Derived
, class Value
, class CategoryOrTraversal
, class Reference
, class Difference
>
class iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, false, false >
# ifdef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
: public boost::detail::iterator_facade_types<
Value, CategoryOrTraversal, Reference, Difference
>::base
# undef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
# endif
{
private:
typedef boost::detail::iterator_facade_types<
Value, CategoryOrTraversal, Reference, Difference
> associated_types;
typedef boost::detail::operator_arrow_dispatch<
Reference
, typename associated_types::pointer
> operator_arrow_dispatch_;
public:
typedef typename associated_types::value_type value_type;
typedef Reference reference;
typedef Difference difference_type;
typedef typename operator_arrow_dispatch_::result_type pointer;
typedef typename associated_types::iterator_category iterator_category;
public:
reference operator*() const
{
return iterator_core_access::dereference(this->derived());
}
pointer operator->() const
{
return operator_arrow_dispatch_::apply(*this->derived());
}
Derived& operator++()
{
iterator_core_access::increment(this->derived());
return this->derived();
}
protected:
//
// Curiously Recurring Template interface.
//
Derived& derived()
{
return *static_cast<Derived*>(this);
}
Derived const& derived() const
{
return *static_cast<Derived const*>(this);
}
};
// Implementation for bidirectional traversal iterators
template <
class Derived
, class Value
, class CategoryOrTraversal
, class Reference
, class Difference
>
class iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, true, false > :
public iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, false, false >
{
public:
Derived& operator--()
{
iterator_core_access::decrement(this->derived());
return this->derived();
}
Derived operator--(int)
{
Derived tmp(this->derived());
--*this;
return tmp;
}
};
// Implementation for random access traversal iterators
template <
class Derived
, class Value
, class CategoryOrTraversal
, class Reference
, class Difference
>
class iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, true, true > :
public iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, true, false >
{
private:
typedef iterator_facade_base< Derived, Value, CategoryOrTraversal, Reference, Difference, true, false > base_type;
public:
typedef typename base_type::reference reference;
typedef typename base_type::difference_type difference_type;
public:
typename boost::detail::operator_brackets_result<Derived, Value, reference>::type
operator[](difference_type n) const
{
typedef boost::detail::use_operator_brackets_proxy<Value, Reference> use_proxy;
return boost::detail::make_operator_brackets_result<Derived>(
this->derived() + n
, use_proxy()
);
}
Derived& operator+=(difference_type n)
{
iterator_core_access::advance(this->derived(), n);
return this->derived();
}
Derived& operator-=(difference_type n)
{
iterator_core_access::advance(this->derived(), -n);
return this->derived();
}
Derived operator-(difference_type x) const
{
Derived result(this->derived());
return result -= x;
}
};
} // namespace detail
//
// iterator_facade - use as a public base class for defining new
// standard-conforming iterators.
@ -561,108 +759,20 @@ namespace boost
, class Reference = Value&
, class Difference = std::ptrdiff_t
>
class iterator_facade
# ifdef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
: public boost::detail::iterator_facade_types<
Value, CategoryOrTraversal, Reference, Difference
>::base
# undef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
# endif
class iterator_facade :
public detail::iterator_facade_base<
Derived,
Value,
CategoryOrTraversal,
Reference,
Difference,
detail::is_traversal_at_least< CategoryOrTraversal, bidirectional_traversal_tag >::value,
detail::is_traversal_at_least< CategoryOrTraversal, random_access_traversal_tag >::value
>
{
private:
//
// Curiously Recurring Template interface.
//
Derived& derived()
{
return *static_cast<Derived*>(this);
}
Derived const& derived() const
{
return *static_cast<Derived const*>(this);
}
typedef boost::detail::iterator_facade_types<
Value, CategoryOrTraversal, Reference, Difference
> associated_types;
typedef boost::detail::operator_arrow_dispatch<
Reference
, typename associated_types::pointer
> operator_arrow_dispatch_;
protected:
protected:
// For use by derived classes
typedef iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Difference> iterator_facade_;
public:
typedef typename associated_types::value_type value_type;
typedef Reference reference;
typedef Difference difference_type;
typedef typename operator_arrow_dispatch_::result_type pointer;
typedef typename associated_types::iterator_category iterator_category;
reference operator*() const
{
return iterator_core_access::dereference(this->derived());
}
pointer operator->() const
{
return operator_arrow_dispatch_::apply(*this->derived());
}
typename boost::detail::operator_brackets_result<Derived,Value,reference>::type
operator[](difference_type n) const
{
typedef boost::detail::use_operator_brackets_proxy<Value,Reference> use_proxy;
return boost::detail::make_operator_brackets_result<Derived>(
this->derived() + n
, use_proxy()
);
}
Derived& operator++()
{
iterator_core_access::increment(this->derived());
return this->derived();
}
Derived& operator--()
{
iterator_core_access::decrement(this->derived());
return this->derived();
}
Derived operator--(int)
{
Derived tmp(this->derived());
--*this;
return tmp;
}
Derived& operator+=(difference_type n)
{
iterator_core_access::advance(this->derived(), n);
return this->derived();
}
Derived& operator-=(difference_type n)
{
iterator_core_access::advance(this->derived(), -n);
return this->derived();
}
Derived operator-(difference_type x) const
{
Derived result(this->derived());
return result -= x;
}
};
template <class I, class V, class TC, class R, class D>
@ -674,13 +784,13 @@ namespace boost
{
typename boost::detail::postfix_increment_result<I,V,R,TC>::type
tmp(*static_cast<I*>(&i));
++i;
return tmp;
}
//
// Comparison operator implementation. The library supplied operators
// enables the user to provide fully interoperable constant/mutable
@ -779,21 +889,50 @@ namespace boost
BOOST_ITERATOR_FACADE_RELATION(==, return, equal)
BOOST_ITERATOR_FACADE_RELATION(!=, return !, equal)
BOOST_ITERATOR_FACADE_RELATION(<, return 0 >, distance_from)
BOOST_ITERATOR_FACADE_RELATION(>, return 0 <, distance_from)
BOOST_ITERATOR_FACADE_RELATION(<=, return 0 >=, distance_from)
BOOST_ITERATOR_FACADE_RELATION(>=, return 0 <=, distance_from)
# undef BOOST_ITERATOR_FACADE_RELATION
# define BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS(op, result_type, return_prefix, base_op) \
BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS_HEAD(inline, op, result_type) \
{ \
/* For those compilers that do not support enable_if */ \
BOOST_STATIC_ASSERT(( \
is_interoperable< Derived1, Derived2 >::value && \
boost::detail::is_traversal_at_least< typename iterator_category< Derived1 >::type, random_access_traversal_tag >::value && \
boost::detail::is_traversal_at_least< typename iterator_category< Derived2 >::type, random_access_traversal_tag >::value \
)); \
return_prefix iterator_core_access::base_op( \
*static_cast<Derived1 const*>(&lhs) \
, *static_cast<Derived2 const*>(&rhs) \
, BOOST_ITERATOR_CONVERTIBLE(Derived2,Derived1) \
); \
}
# define BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(op, return_prefix, base_op) \
BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS( \
op \
, boost::detail::always_bool2 \
, return_prefix \
, base_op \
)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(<, return 0 >, distance_from)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(>, return 0 <, distance_from)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(<=, return 0 >=, distance_from)
BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION(>=, return 0 <=, distance_from)
# undef BOOST_ITERATOR_FACADE_RANDOM_ACCESS_RELATION
// operator- requires an additional part in the static assertion
BOOST_ITERATOR_FACADE_INTEROP(
BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS(
-
, boost::detail::choose_difference_type
, return
, distance_from
)
# undef BOOST_ITERATOR_FACADE_INTEROP
# undef BOOST_ITERATOR_FACADE_INTEROP_HEAD
# undef BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS
# define BOOST_ITERATOR_FACADE_PLUS(args) \
BOOST_ITERATOR_FACADE_PLUS_HEAD(inline, args) \
@ -811,9 +950,14 @@ BOOST_ITERATOR_FACADE_PLUS((
typename Derived::difference_type n
, iterator_facade<Derived, V, TC, R, D> const& i
))
# undef BOOST_ITERATOR_FACADE_PLUS
# undef BOOST_ITERATOR_FACADE_PLUS_HEAD
# undef BOOST_ITERATOR_FACADE_INTEROP_HEAD
# undef BOOST_ITERATOR_FACADE_INTEROP_RANDOM_ACCESS_HEAD
# undef BOOST_ITERATOR_FACADE_INTEROP_HEAD_IMPL
} // namespace boost
#include <boost/iterator/detail/config_undef.hpp>