zip_view/detail/prior_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_PRIOR_IMPL_20060124_2006)
0009 #define FUSION_PRIOR_IMPL_20060124_2006
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/fusion/view/zip_view/zip_view_iterator_fwd.hpp>
0013 #include <boost/fusion/iterator/prior.hpp>
0014 #include <boost/fusion/algorithm/transformation/transform.hpp>
0015 #include <boost/fusion/support/unused.hpp>
0016 #include <boost/mpl/eval_if.hpp>
0017 #include <boost/mpl/identity.hpp>
0018 #include <boost/type_traits/is_same.hpp>
0019 #include <boost/type_traits/remove_reference.hpp>
0020 #include <boost/type_traits/remove_const.hpp>
0021
0022 namespace boost { namespace fusion {
0023
0024     struct zip_view_iterator_tag;
0025
0026     namespace detail
0027     {
0028         struct poly_prior
0029         {
0030             template<typename Sig>
0031             struct result;
0032
0033             template<typename It>
0034             struct result<poly_prior(It)>
0035             {
0036                 typedef typename remove_const<
0037                     typename remove_reference<It>::type>::type it;
0038                 typedef typename mpl::eval_if<is_same<it, unused_type>,
0039                     mpl::identity<unused_type>,
0040                     result_of::prior<it> >::type type;
0041             };
0042
0043             template<typename It>
0044             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0045             typename result<poly_prior(It)>::type
0046             operator()(const It& it) const
0047             {
0048                 return fusion::prior(it);
0049             }
0050
0051             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0052             unused_type operator()(unused_type const&) const
0053             {
0054                 return unused_type();
0055             }
0056         };
0057     }
0058
0059     namespace extension
0060     {
0061         template<typename Tag>
0062         struct prior_impl;
0063
0064         template<>
0065         struct prior_impl<zip_view_iterator_tag>
0066         {
0067             template<typename Iterator>
0068             struct apply
0069             {
0070                 typedef zip_view_iterator<
0071                     typename result_of::transform<typename Iterator::iterators, detail::poly_prior>::type,
0072                     typename Iterator::category> type;
0073
0074                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0075                 static type
0076                 call(Iterator const& it)
0077
0078                 {
0079                     return type(
0080                         fusion::transform(it.iterators_, detail::poly_prior()));
0081                 }
0082             };
0083         };
0084     }
0085 }}
0086
0087 #endif