boost_tuple/detail/at_impl.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
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 #if !defined(BOOST_FUSION_AT_IMPL_09262006_1920)
0008 #define BOOST_FUSION_AT_IMPL_09262006_1920
0009
0010 #include <boost/fusion/support/config.hpp>
0011 #include <boost/tuple/tuple.hpp>
0012 #include <boost/mpl/if.hpp>
0013
0014 namespace boost { namespace fusion
0015 {
0016     struct boost_tuple_tag;
0017
0018     namespace extension
0019     {
0020         template<typename T>
0021         struct at_impl;
0022
0023         template <>
0024         struct at_impl<boost_tuple_tag>
0025         {
0026             template <typename Sequence, typename N>
0027             struct apply
0028             {
0029                 typedef typename
0030                     tuples::element<N::value, Sequence>::type
0031                 element;
0032
0033                 typedef typename
0034                     mpl::if_<
0035                         is_const<Sequence>
0036                       , typename tuples::access_traits<element>::const_type
0037                       , typename tuples::access_traits<element>::non_const_type
0038                     >::type
0039                 type;
0040
0041                 BOOST_FUSION_GPU_ENABLED
0042                 static type
0043                 call(Sequence& seq)
0044                 {
0045                     return tuples::get<N::value>(seq);
0046                 }
0047             };
0048         };
0049     }
0050 }}
0051
0052 #endif