/*=============================================================================

    Copyright (c) 2001-2006 Joel de Guzman

    Copyright (c) 2005-2006 Dan Marsden



    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(BOOST_FUSION_AT_IMPL_24122005_1807)

#define BOOST_FUSION_AT_IMPL_24122005_1807



#include <boost/fusion/support/detail/access.hpp>

#include <boost/mpl/assert.hpp>

#include <boost/mpl/int.hpp>



namespace boost { namespace fusion

{

    struct struct_tag;



    namespace extension

    {

        template<typename T>

        struct at_impl;



        template <typename Struct, int N>

        struct struct_member;



        template <typename Struct>

        struct struct_size;



        template <>

        struct at_impl<struct_tag>

        {

            template <typename Sequence, typename N>

            struct apply

            {

                static int const n_value = N::value;

                BOOST_MPL_ASSERT_RELATION(

                    n_value, <=, extension::struct_size<Sequence>::value);



                typedef typename

                    extension::struct_member<Sequence, N::value>

                element;



                typedef typename

                    mpl::eval_if<

                        is_const<Sequence>

                      , detail::cref_result<element>

                      , detail::ref_result<element>

                    >::type

                type;



                static type

                call(Sequence& seq)

                {

                    return extension::

                        struct_member<Sequence, N::value>::call(seq);

                }

            };

        };

    }

}}



#endif

