advance.hpp

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/*=============================================================================
    Copyright (c) 2001-2006 Joel de Guzman

    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)
==============================================================================*/
#if !defined(FUSION_ADVANCE_09172005_1146)
#define FUSION_ADVANCE_09172005_1146

#include <boost/fusion/iterator/detail/advance.hpp>
#include <boost/fusion/support/category_of.hpp>

#include <boost/mpl/int.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/fusion/support/tag_of.hpp>

namespace boost { namespace fusion
{
    struct random_access_traversal_tag;
        
    // Special tags:
    struct iterator_facade_tag; // iterator facade tag
    struct array_iterator_tag; // boost::array iterator tag
    struct mpl_iterator_tag; // mpl sequence iterator tag
    struct std_pair_iterator_tag; // std::pair iterator tag

    namespace extension
    {
        template <typename Tag>
        struct advance_impl
        {
            // default implementation
            template <typename Iterator, typename N>
            struct apply :
                mpl::if_c<
                    (N::value > 0)
                  , advance_detail::forward<Iterator, N::value>
                  , advance_detail::backward<Iterator, N::value>
                >::type
            {
                BOOST_MPL_ASSERT_NOT((traits::is_random_access<Iterator>));
            };
        };

        template <>
        struct advance_impl<iterator_facade_tag>
        {
            template <typename Iterator, typename N>
            struct apply : Iterator::template advance<Iterator, N> {};
        };

        template <>
        struct advance_impl<array_iterator_tag>;

        template <>
        struct advance_impl<mpl_iterator_tag>;

        template <>
        struct advance_impl<std_pair_iterator_tag>;
    }
    
    namespace result_of
    {
        template <typename Iterator, int N>
        struct advance_c
            : extension::advance_impl<typename detail::tag_of<Iterator>::type>::template apply<Iterator, mpl::int_<N> >
        {};

        template <typename Iterator, typename N>
        struct advance
            : extension::advance_impl<typename detail::tag_of<Iterator>::type>::template apply<Iterator, N>
        {};
    }

    template <int N, typename Iterator>
    inline typename result_of::advance_c<Iterator, N>::type const
    advance_c(Iterator const& i)
    {
        return result_of::advance_c<Iterator, N>::call(i);
    }

    template<typename N, typename Iterator>
    inline typename result_of::advance<Iterator, N>::type const
    advance(Iterator const& i)
    {
        return result_of::advance<Iterator, N>::call(i);
    }

}} // namespace boost::fusion

#endif