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// Copyright David Abrahams 2003. 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)
#ifndef FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
# define FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
# include <boost/iterator/iterator_categories.hpp>
# include <boost/mpl/or.hpp> // used in iterator_tag inheritance logic
# include <boost/mpl/and.hpp>
# include <boost/mpl/if.hpp>
# include <boost/mpl/eval_if.hpp>
# include <boost/mpl/identity.hpp>
# include <boost/mpl/assert.hpp>
# include <boost/type_traits/is_same.hpp>
# include <boost/type_traits/is_const.hpp>
# include <boost/type_traits/is_reference.hpp>
# include <boost/type_traits/is_convertible.hpp>
# include <boost/type_traits/is_same.hpp>
# include <boost/iterator/detail/config_def.hpp> // try to keep this last
# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
# include <boost/detail/indirect_traits.hpp>
# endif
//
// iterator_category deduction for iterator_facade
//
namespace boost {
namespace iterators {
// forward declaration
struct use_default;
namespace detail {
struct input_output_iterator_tag
: std::input_iterator_tag
{
// Using inheritance for only input_iterator_tag helps to avoid
// ambiguities when a stdlib implementation dispatches on a
// function which is overloaded on both input_iterator_tag and
// output_iterator_tag, as STLPort does, in its __valid_range
// function. I claim it's better to avoid the ambiguity in these
// cases.
operator std::output_iterator_tag() const
{
return std::output_iterator_tag();
}
};
//
// True iff the user has explicitly disabled writability of this
// iterator. Pass the iterator_facade's Value parameter and its
// nested ::reference type.
//
template <class ValueParam, class Reference>
struct iterator_writability_disabled
# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY // Adding Thomas' logic?
: mpl::or_<
is_const<Reference>
, boost::detail::indirect_traits::is_reference_to_const<Reference>
, is_const<ValueParam>
>
# else
: is_const<ValueParam>
# endif
{};
//
// Convert an iterator_facade's traversal category, Value parameter,
// and ::reference type to an appropriate old-style category.
//
// Due to changeset 21683, this now never results in a category convertible
// to output_iterator_tag.
//
// Change at: https://svn.boost.org/trac/boost/changeset/21683
template <class Traversal, class ValueParam, class Reference>
struct iterator_facade_default_category
: mpl::eval_if<
mpl::and_<
is_reference<Reference>
, is_convertible<Traversal,forward_traversal_tag>
>
, mpl::eval_if<
is_convertible<Traversal,random_access_traversal_tag>
, mpl::identity<std::random_access_iterator_tag>
, mpl::if_<
is_convertible<Traversal,bidirectional_traversal_tag>
, std::bidirectional_iterator_tag
, std::forward_iterator_tag
>
>
, typename mpl::eval_if<
mpl::and_<
is_convertible<Traversal, single_pass_traversal_tag>
// check for readability
, is_convertible<Reference, ValueParam>
>
, mpl::identity<std::input_iterator_tag>
, mpl::identity<Traversal>
>
>
{
};
// True iff T is convertible to an old-style iterator category.
template <class T>
struct is_iterator_category
: mpl::or_<
is_convertible<T,std::input_iterator_tag>
, is_convertible<T,std::output_iterator_tag>
>
{
};
template <class T>
struct is_iterator_traversal
: is_convertible<T,incrementable_traversal_tag>
{};
//
// A composite iterator_category tag convertible to Category (a pure
// old-style category) and Traversal (a pure traversal tag).
// Traversal must be a strict increase of the traversal power given by
// Category.
//
template <class Category, class Traversal>
struct iterator_category_with_traversal
: Category, Traversal
{
// Make sure this isn't used to build any categories where
// convertibility to Traversal is redundant. Should just use the
// Category element in that case.
BOOST_MPL_ASSERT_NOT((
is_convertible<
typename iterator_category_to_traversal<Category>::type
, Traversal
>));
BOOST_MPL_ASSERT((is_iterator_category<Category>));
BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
BOOST_MPL_ASSERT_NOT((is_iterator_traversal<Category>));
# if !BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1310))
BOOST_MPL_ASSERT((is_iterator_traversal<Traversal>));
# endif
};
// Computes an iterator_category tag whose traversal is Traversal and
// which is appropriate for an iterator
template <class Traversal, class ValueParam, class Reference>
struct facade_iterator_category_impl
{
BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
typedef typename iterator_facade_default_category<
Traversal,ValueParam,Reference
>::type category;
typedef typename mpl::if_<
is_same<
Traversal
, typename iterator_category_to_traversal<category>::type
>
, category
, iterator_category_with_traversal<category,Traversal>
>::type type;
};
//
// Compute an iterator_category for iterator_facade
//
template <class CategoryOrTraversal, class ValueParam, class Reference>
struct facade_iterator_category
: mpl::eval_if<
is_iterator_category<CategoryOrTraversal>
, mpl::identity<CategoryOrTraversal> // old-style categories are fine as-is
, facade_iterator_category_impl<CategoryOrTraversal,ValueParam,Reference>
>
{
};
}}} // namespace boost::iterators::detail
# include <boost/iterator/detail/config_undef.hpp>
#endif // FACADE_ITERATOR_CATEGORY_DWA20031118_HPP