fusion/iterator/distance.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_DISTANCE_09172005_0721)
0008 #define FUSION_DISTANCE_09172005_0721
0009
0010 #include <boost/fusion/support/config.hpp>
0011 #include <boost/fusion/iterator/detail/distance.hpp>
0012 #include <boost/fusion/support/category_of.hpp>
0013
0014 #include <boost/mpl/int.hpp>
0015 #include <boost/mpl/assert.hpp>
0016 #include <boost/type_traits/is_same.hpp>
0017
0018 #include <boost/fusion/support/tag_of.hpp>
0019
0020 namespace boost { namespace fusion
0021 {
0022     struct random_access_traversal_tag;
0023
0024     // Special tags:
0025     struct iterator_facade_tag; // iterator facade tag
0026     struct boost_array_iterator_tag; // boost::array iterator tag
0027     struct mpl_iterator_tag; // mpl sequence iterator tag
0028     struct std_pair_iterator_tag; // std::pair iterator tag
0029
0030     namespace extension
0031     {
0032         template <typename Tag>
0033         struct distance_impl
0034         {
0035             // default implementation
0036             template <typename First, typename Last>
0037             struct apply : distance_detail::linear_distance<First, Last>
0038             {};
0039         };
0040
0041         template <>
0042         struct distance_impl<iterator_facade_tag>
0043         {
0044             template <typename First, typename Last>
0045             struct apply : First::template distance<First, Last> {};
0046         };
0047
0048         template <>
0049         struct distance_impl<boost_array_iterator_tag>;
0050
0051         template <>
0052         struct distance_impl<mpl_iterator_tag>;
0053
0054         template <>
0055         struct distance_impl<std_pair_iterator_tag>;
0056     }
0057
0058     namespace result_of
0059     {
0060         template <typename First, typename Last>
0061         struct distance
0062           : extension::distance_impl<typename detail::tag_of<First>::type>::
0063                 template apply<First, Last>
0064         {
0065             typedef typename extension::distance_impl<typename detail::tag_of<First>::type>::
0066             template apply<First, Last>::type distance_application;
0067             BOOST_STATIC_CONSTANT(int, value = distance_application::value);
0068         };
0069     }
0070
0071     template <typename First, typename Last>
0072     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0073     inline typename result_of::distance<First, Last>::type
0074     distance(First const& a, Last const& b)
0075     {
0076         return result_of::distance<First, Last>::call(a,b);
0077     }
0078 }}
0079
0080 #endif