zip_view/detail/distance_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_DISTANCE_IMPL_20060124_2033)
0009 #define FUSION_DISTANCE_IMPL_20060124_2033
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/mpl/eval_if.hpp>
0013 #include <boost/mpl/placeholders.hpp>
0014 #include <boost/mpl/assert.hpp>
0015 #include <boost/fusion/iterator/distance.hpp>
0016 #include <boost/fusion/support/category_of.hpp>
0017 #include <boost/fusion/algorithm/query/find_if.hpp>
0018 #include <boost/fusion/sequence/intrinsic/end.hpp>
0019 #include <boost/fusion/sequence/intrinsic/value_at.hpp>
0020 #include <boost/type_traits/is_same.hpp>
0021
0022 namespace boost { namespace fusion {
0023
0024     struct zip_view_iterator_tag;
0025
0026     struct random_access_iterator_tag;
0027
0028     namespace detail
0029     {
0030         template<typename FoundIt, typename SearchIt>
0031         struct best_distance
0032         {
0033             typedef typename result_of::find_if<
0034                 typename SearchIt::iterators, is_same<traits::category_of<mpl::_>, random_access_iterator_tag> > finder;
0035
0036             BOOST_MPL_ASSERT_NOT((is_same<typename finder::type, result_of::end<typename SearchIt::iterators> >));
0037
0038             typedef typename result_of::distance<FoundIt, typename finder::type>::type type;
0039         };
0040
0041         template<typename It1, typename It2>
0042         struct default_distance
0043             : result_of::distance<
0044             typename result_of::value_at_c<typename It1::iterators, 0>::type,
0045             typename result_of::value_at_c<typename It2::iterators, 0>::type>
0046         {};
0047
0048         template<typename It1, typename It2>
0049         struct zip_view_iterator_distance
0050         {
0051             typedef typename result_of::find_if<
0052                 typename It1::iterators, is_same<traits::category_of<mpl::_>, random_access_iterator_tag> > finder;
0053
0054             typedef typename mpl::eval_if<
0055                 is_same<typename finder::type, typename result_of::end<typename It1::iterators>::type>,
0056                 detail::default_distance<It1, It2> ,
0057                 detail::best_distance<typename finder::type, It2> >::type type;
0058         };
0059     }
0060
0061     namespace extension
0062     {
0063         template<typename Tag>
0064         struct distance_impl;
0065
0066         template<>
0067         struct distance_impl<zip_view_iterator_tag>
0068         {
0069             template<typename It1, typename It2>
0070             struct apply
0071                 : detail::zip_view_iterator_distance<It1, It2>::type
0072             {
0073                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0074                 static typename detail::zip_view_iterator_distance<It1, It2>::type
0075                 call(It1 const& /*it1*/, It2 const& /*it2*/)
0076                 {
0077                     return typename detail::zip_view_iterator_distance<It1, It2>::type();
0078                 }
0079             };
0080         };
0081     }
0082 }}
0083
0084 #endif