reverse_view/detail/at_impl.hpp

0001 /*=============================================================================
0002     Copyright (c) 2009 Christopher Schmidt
0003
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 ==============================================================================*/
0007
0008 #ifndef BOOST_FUSION_VIEW_REVERSE_VIEW_DETAIL_AT_IMPL_HPP
0009 #define BOOST_FUSION_VIEW_REVERSE_VIEW_DETAIL_AT_IMPL_HPP
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/fusion/sequence/intrinsic/at.hpp>
0013 #include <boost/mpl/minus.hpp>
0014 #include <boost/mpl/int.hpp>
0015
0016 namespace boost { namespace fusion { namespace extension
0017 {
0018     template <typename>
0019     struct at_impl;
0020
0021     template <>
0022     struct at_impl<reverse_view_tag>
0023     {
0024         template <typename Seq, typename N>
0025         struct apply
0026         {
0027             typedef mpl::minus<typename Seq::size, mpl::int_<1>, N> real_n;
0028
0029             typedef typename
0030                 result_of::at<typename Seq::seq_type, real_n>::type
0031             type;
0032
0033             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0034             static type
0035             call(Seq& seq)
0036             {
0037                 return fusion::at<real_n>(seq.seq);
0038             }
0039         };
0040     };
0041 }}}
0042
0043 #endif