/*=============================================================================
    Copyright (c) 2001-2011 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_BEGIN_IMPL_07162005_0115)
#define FUSION_BEGIN_IMPL_07162005_0115

#include <boost/fusion/support/config.hpp>
#include <boost/fusion/iterator/equal_to.hpp>
#include <boost/mpl/if.hpp>

namespace boost {
namespace fusion {
struct joint_view_tag;

template <typename Category, typename First, typename Last, typename Concat>
struct joint_view_iterator;

namespace extension {
template <typename Tag>
struct begin_impl;

template <>
struct begin_impl<joint_view_tag>
{
    template <typename Sequence>
    struct apply
    {
        typedef typename Sequence::first_type first_type;
        typedef typename Sequence::last_type last_type;
        typedef typename Sequence::concat_type concat_type;
        typedef typename Sequence::category category;
        typedef result_of::equal_to<first_type, last_type> equal_to;

        typedef typename
        mpl::if_<
        equal_to
        , concat_type
        , joint_view_iterator<category, first_type, last_type, concat_type>
        >::type
        type;

        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
        static type
        call(Sequence& s, mpl::true_)
        {
            return s.concat();
        }

        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
        static type
        call(Sequence& s, mpl::false_)
        {
            return type(s.first(), s.concat());
        }

        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
        static type
        call(Sequence& s)
        {
            return call(s, equal_to());
        }
    };
};
}
}
}

#endif
