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// (C) Copyright Jeremy Siek 2002.
// Distributed under 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 BOOST_ITERATOR_CATEGORIES_HPP
# define BOOST_ITERATOR_CATEGORIES_HPP
# include <boost/config.hpp>
# include <boost/detail/iterator.hpp>
# include <boost/iterator/detail/config_def.hpp>
# include <boost/detail/workaround.hpp>
# include <boost/mpl/eval_if.hpp>
# include <boost/mpl/identity.hpp>
# include <boost/mpl/placeholders.hpp>
# include <boost/mpl/aux_/lambda_support.hpp>
# include <boost/type_traits/is_convertible.hpp>
# include <boost/static_assert.hpp>
namespace boost {
//
// Traversal Categories
//
struct no_traversal_tag {};
struct incrementable_traversal_tag
: no_traversal_tag
{
// incrementable_traversal_tag() {}
// incrementable_traversal_tag(std::output_iterator_tag const&) {};
};
struct single_pass_traversal_tag
: incrementable_traversal_tag
{
// single_pass_traversal_tag() {}
// single_pass_traversal_tag(std::input_iterator_tag const&) {};
};
struct forward_traversal_tag
: single_pass_traversal_tag
{
// forward_traversal_tag() {}
// forward_traversal_tag(std::forward_iterator_tag const&) {};
};
struct bidirectional_traversal_tag
: forward_traversal_tag
{
// bidirectional_traversal_tag() {};
// bidirectional_traversal_tag(std::bidirectional_iterator_tag const&) {};
};
struct random_access_traversal_tag
: bidirectional_traversal_tag
{
// random_access_traversal_tag() {};
// random_access_traversal_tag(std::random_access_iterator_tag const&) {};
};
namespace detail
{
//
// Convert a "strictly old-style" iterator category to a traversal
// tag. This is broken out into a separate metafunction to reduce
// the cost of instantiating iterator_category_to_traversal, below,
// for new-style types.
//
template <class Cat>
struct old_category_to_traversal
: mpl::eval_if<
is_convertible<Cat,std::random_access_iterator_tag>
, mpl::identity<random_access_traversal_tag>
, mpl::eval_if<
is_convertible<Cat,std::bidirectional_iterator_tag>
, mpl::identity<bidirectional_traversal_tag>
, mpl::eval_if<
is_convertible<Cat,std::forward_iterator_tag>
, mpl::identity<forward_traversal_tag>
, mpl::eval_if<
is_convertible<Cat,std::input_iterator_tag>
, mpl::identity<single_pass_traversal_tag>
, mpl::eval_if<
is_convertible<Cat,std::output_iterator_tag>
, mpl::identity<incrementable_traversal_tag>
, void
>
>
>
>
>
{};
# if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
template <>
struct old_category_to_traversal<int>
{
typedef int type;
};
# endif
template <class Traversal>
struct pure_traversal_tag
: mpl::eval_if<
is_convertible<Traversal,random_access_traversal_tag>
, mpl::identity<random_access_traversal_tag>
, mpl::eval_if<
is_convertible<Traversal,bidirectional_traversal_tag>
, mpl::identity<bidirectional_traversal_tag>
, mpl::eval_if<
is_convertible<Traversal,forward_traversal_tag>
, mpl::identity<forward_traversal_tag>
, mpl::eval_if<
is_convertible<Traversal,single_pass_traversal_tag>
, mpl::identity<single_pass_traversal_tag>
, mpl::eval_if<
is_convertible<Traversal,incrementable_traversal_tag>
, mpl::identity<incrementable_traversal_tag>
, void
>
>
>
>
>
{
};
# if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
template <>
struct pure_traversal_tag<int>
{
typedef int type;
};
# endif
} // namespace detail
//
// Convert an iterator category into a traversal tag
//
template <class Cat>
struct iterator_category_to_traversal
: mpl::eval_if< // if already convertible to a traversal tag, we're done.
is_convertible<Cat,incrementable_traversal_tag>
, mpl::identity<Cat>
, detail::old_category_to_traversal<Cat>
>
{};
// Trait to get an iterator's traversal category
template <class Iterator = mpl::_1>
struct iterator_traversal
: iterator_category_to_traversal<
typename boost::detail::iterator_traits<Iterator>::iterator_category
>
{};
# ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT
// Hack because BOOST_MPL_AUX_LAMBDA_SUPPORT doesn't seem to work
// out well. Instantiating the nested apply template also
// requires instantiating iterator_traits on the
// placeholder. Instead we just specialize it as a metafunction
// class.
template <>
struct iterator_traversal<mpl::_1>
{
template <class T>
struct apply : iterator_traversal<T>
{};
};
template <>
struct iterator_traversal<mpl::_>
: iterator_traversal<mpl::_1>
{};
# endif
} // namespace boost
#include <boost/iterator/detail/config_undef.hpp>
#endif // BOOST_ITERATOR_CATEGORIES_HPP
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