/*=============================================================================
    Copyright (c) 2001-2013 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(BOOST_FUSION_MAP_DETAIL_AT_KEY_IMPL_02042013_0821)
#define BOOST_FUSION_MAP_DETAIL_AT_KEY_IMPL_02042013_0821

#include <boost/fusion/support/config.hpp>
#include <boost/fusion/support/detail/access.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/mpl/at.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/utility/declval.hpp>

namespace boost {
namespace fusion {
struct map_tag;

namespace extension {
template <typename Tag>
struct at_key_impl;

template <>
struct at_key_impl<map_tag>
{
    template <typename Sequence, typename Key>
    struct apply
    {
        typedef
        decltype(boost::declval<Sequence>().get(mpl::identity<Key>()))
        type;

        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
        static type
        call(Sequence& m)
        {
            return m.get(mpl::identity<Key>());
        }
    };

    template <typename Sequence, typename Key>
    struct apply<Sequence const, Key>
    {
        typedef
        decltype(boost::declval<Sequence const>().get(mpl::identity<Key>()))
        type;

        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
        static type
        call(Sequence const& m)
        {
            return m.get(mpl::identity<Key>());
        }
    };
};
}
}
}

#endif
