zip_view/detail/begin_impl.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
0003     Copyright (c) 2006 Dan Marsden
0004
0005     Distributed under the Boost Software License, Version 1.0. (See accompanying
0006     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 ==============================================================================*/
0008 #if !defined(FUSION_BEGIN_IMPL_20060123_2147)
0009 #define FUSION_BEGIN_IMPL_20060123_2147
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/fusion/sequence/intrinsic/begin.hpp>
0013 #include <boost/fusion/view/zip_view/zip_view_iterator_fwd.hpp>
0014 #include <boost/fusion/algorithm/transformation/transform.hpp>
0015 #include <boost/type_traits/remove_reference.hpp>
0016 #include <boost/type_traits/is_reference.hpp>
0017 #include <boost/type_traits/is_same.hpp>
0018 #include <boost/mpl/assert.hpp>
0019 #include <boost/mpl/eval_if.hpp>
0020 #include <boost/mpl/identity.hpp>
0021 #include <boost/fusion/support/unused.hpp>
0022
0023 namespace boost { namespace fusion {
0024
0025     struct zip_view_tag;
0026
0027     namespace detail
0028     {
0029         struct poly_begin
0030         {
0031             template<typename T>
0032             struct result;
0033
0034             template<typename SeqRef>
0035             struct result<poly_begin(SeqRef)>
0036                 : mpl::eval_if<is_same<SeqRef, unused_type const&>,
0037                                mpl::identity<unused_type>,
0038                                result_of::begin<typename remove_reference<SeqRef>::type> >
0039             {
0040                 BOOST_MPL_ASSERT((is_reference<SeqRef>));
0041             };
0042
0043             template<typename Seq>
0044             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0045             typename result<poly_begin(Seq&)>::type
0046             operator()(Seq& seq) const
0047             {
0048                 return fusion::begin(seq);
0049             }
0050
0051             template<typename Seq>
0052             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0053             typename result<poly_begin(Seq const&)>::type
0054             operator()(Seq const& seq) const
0055             {
0056                 return fusion::begin(seq);
0057             }
0058
0059             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0060             unused_type operator()(unused_type const&) const
0061             {
0062                 return unused_type();
0063             }
0064         };
0065     }
0066
0067     namespace extension
0068     {
0069         template<typename Tag>
0070         struct begin_impl;
0071
0072         template<>
0073         struct begin_impl<zip_view_tag>
0074         {
0075             template<typename Sequence>
0076             struct apply
0077             {
0078                 typedef zip_view_iterator<
0079                     typename result_of::transform<typename Sequence::sequences, detail::poly_begin>::type,
0080                     typename Sequence::category> type;
0081
0082                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0083                 static type
0084                 call(Sequence& sequence)
0085                 {
0086                     return type(
0087                         fusion::transform(sequence.sequences_, detail::poly_begin()));
0088                 }
0089             };
0090
0091
0092
0093         };
0094     }
0095 }}
0096
0097 #endif