Chris@16: 
Chris@16: #ifndef BOOST_MPL_AUX_ERASE_IMPL_HPP_INCLUDED
Chris@16: #define BOOST_MPL_AUX_ERASE_IMPL_HPP_INCLUDED
Chris@16: 
Chris@16: // Copyright Aleksey Gurtovoy 2000-2004
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. 
Chris@16: // (See accompanying file LICENSE_1_0.txt or copy at 
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/mpl for documentation.
Chris@16: 
Chris@101: // $Id$
Chris@101: // $Date$
Chris@101: // $Revision$
Chris@16: 
Chris@16: #include <boost/mpl/clear.hpp>
Chris@16: #include <boost/mpl/push_front.hpp>
Chris@16: #include <boost/mpl/reverse_fold.hpp>
Chris@16: #include <boost/mpl/iterator_range.hpp>
Chris@16: #include <boost/mpl/next.hpp>
Chris@16: #include <boost/mpl/aux_/na.hpp>
Chris@16: 
Chris@16: namespace boost { namespace mpl {
Chris@16: 
Chris@16: // default implementation; conrete sequences might override it by 
Chris@16: // specializing either the 'erase_impl' or the primary 'erase' template
Chris@16: 
Chris@16: template< typename Tag >
Chris@16: struct erase_impl
Chris@16: {
Chris@16:     template<
Chris@16:           typename Sequence
Chris@16:         , typename First
Chris@16:         , typename Last
Chris@16:         >
Chris@16:     struct apply
Chris@16:     {
Chris@16:         typedef typename if_na< Last,typename next<First>::type >::type last_;
Chris@16:         
Chris@16:         // 1st half: [begin, first)
Chris@16:         typedef iterator_range<
Chris@16:               typename begin<Sequence>::type
Chris@16:             , First
Chris@16:             > first_half_;
Chris@16: 
Chris@16:         // 2nd half: [last, end) ... that is, [last + 1, end)
Chris@16:         typedef iterator_range<
Chris@16:               last_
Chris@16:             , typename end<Sequence>::type
Chris@16:             > second_half_;
Chris@16: 
Chris@16:         typedef typename reverse_fold<
Chris@16:               second_half_
Chris@16:             , typename clear<Sequence>::type
Chris@16:             , push_front<_,_>
Chris@16:             >::type half_sequence_;
Chris@16: 
Chris@16:         typedef typename reverse_fold<
Chris@16:               first_half_
Chris@16:             , half_sequence_
Chris@16:             , push_front<_,_>
Chris@16:             >::type type;
Chris@16:     };
Chris@16: };
Chris@16: 
Chris@16: }}
Chris@16: 
Chris@16: #endif // BOOST_MPL_AUX_ERASE_IMPL_HPP_INCLUDED