
#ifndef BOOST_MPL_INSERT_IMPL_HPP_INCLUDED
#define BOOST_MPL_INSERT_IMPL_HPP_INCLUDED

// Copyright Aleksey Gurtovoy 2000-2004
//
// 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)
//
// See http://www.boost.org/libs/mpl for documentation.

// $Id$
// $Date$
// $Revision$

#include <boost/mpl/reverse_fold.hpp>
#include <boost/mpl/iterator_range.hpp>
#include <boost/mpl/clear.hpp>
#include <boost/mpl/push_front.hpp>
#include <boost/mpl/aux_/na_spec.hpp>
#include <boost/mpl/aux_/traits_lambda_spec.hpp>
#include <boost/type_traits/is_same.hpp>

namespace boost {
namespace mpl {

// default implementation; conrete sequences might override it by
// specializing either the 'insert_impl' or the primary 'insert' template

template< typename Tag >
struct insert_impl
{
    template<
        typename Sequence
    , typename Pos
    , typename T
    >
    struct apply
    {
        typedef iterator_range<
        typename begin<Sequence>::type
        , Pos
        > first_half_;

        typedef iterator_range<
        Pos
        , typename end<Sequence>::type
        > second_half_;

        typedef typename reverse_fold<
        second_half_
        , typename clear<Sequence>::type
        , push_front<_,_>
        >::type half_sequence_;

        typedef typename reverse_fold<
        first_half_
        , typename push_front<half_sequence_,T>::type
        , push_front<_,_>
        >::type type;
    };
};

BOOST_MPL_ALGORITM_TRAITS_LAMBDA_SPEC(3,insert_impl)

}
}

#endif // BOOST_MPL_INSERT_IMPL_HPP_INCLUDED
