

#ifndef BOOST_MPL_AUX_ERASE_IMPL_HPP_INCLUDED

#define BOOST_MPL_AUX_ERASE_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.



// $Source$

// $Date: 2004-09-02 11:41:37 -0400 (Thu, 02 Sep 2004) $

// $Revision: 24874 $



#include <boost/mpl/clear.hpp>

#include <boost/mpl/push_front.hpp>

#include <boost/mpl/reverse_fold.hpp>

#include <boost/mpl/iterator_range.hpp>

#include <boost/mpl/next.hpp>

#include <boost/mpl/aux_/na.hpp>



namespace boost { namespace mpl {



// default implementation; conrete sequences might override it by 

// specializing either the 'erase_impl' or the primary 'erase' template



template< typename Tag >

struct erase_impl

{

    template<

          typename Sequence

        , typename First

        , typename Last

        >

    struct apply

    {

        typedef typename if_na< Last,typename next<First>::type >::type last_;

        

        // 1st half: [begin, first)

        typedef iterator_range<

              typename begin<Sequence>::type

            , First

            > first_half_;



        // 2nd half: [last, end) ... that is, [last + 1, end)

        typedef iterator_range<

              last_

            , 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_

            , half_sequence_

            , push_front<_,_>

            >::type type;

    };

};



}}



#endif // BOOST_MPL_AUX_ERASE_IMPL_HPP_INCLUDED

