/*=============================================================================
    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_DISTANCE_09172005_0730)
#define FUSION_DISTANCE_09172005_0730

#include <boost/fusion/support/config.hpp>
#include <boost/mpl/int.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/fusion/iterator/next.hpp>
#include <boost/fusion/iterator/equal_to.hpp>

namespace boost {
namespace fusion {
namespace distance_detail {
// Default distance implementation, linear
// search for the Last iterator.

template <typename First, typename Last>
struct linear_distance;

template <typename First, typename Last>
struct next_distance
{
    typedef typename
    mpl::next<
    typename linear_distance<
    typename result_of::next<First>::type
    , Last
    >::type
    >::type
    type;
};

template <typename First, typename Last>
struct linear_distance
    : mpl::eval_if<
      result_of::equal_to<First, Last>
    , mpl::identity<mpl::int_<0> >
    , next_distance<First, Last>
    >::type
{
    typedef typename
    mpl::eval_if<
    result_of::equal_to<First, Last>
    , mpl::identity<mpl::int_<0> >
    , next_distance<First, Last>
    >::type
    type;

    BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
    static type
    call(First const&, Last const&)
    {
        return type();
    }
};

}
}
}

#endif
