sequence/intrinsic/front.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(FUSION_FRONT_09162005_0343)
0008 #define FUSION_FRONT_09162005_0343
0009
0010 #include <boost/fusion/support/config.hpp>
0011 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
0012 #include <boost/fusion/sequence/intrinsic/begin.hpp>
0013 #include <boost/fusion/iterator/deref.hpp>
0014 #include <boost/mpl/bool.hpp>
0015
0016 namespace boost { namespace fusion
0017 {
0018     struct fusion_sequence_tag;
0019
0020     namespace result_of
0021     {
0022         template <typename Sequence>
0023         struct front
0024             : result_of::deref<typename result_of::begin<Sequence>::type>
0025         {};
0026     }
0027
0028     template <typename Sequence>
0029     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0030     inline typename result_of::front<Sequence>::type
0031     front(Sequence& seq)
0032     {
0033         return *fusion::begin(seq);
0034     }
0035
0036     template <typename Sequence>
0037     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0038     inline typename result_of::front<Sequence const>::type
0039     front(Sequence const& seq)
0040     {
0041         return *fusion::begin(seq);
0042     }
0043 }}
0044
0045 #endif