boost/fusion/iterator/distance.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2006 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #if !defined(FUSION_DISTANCE_09172005_0721)
   8 #define FUSION_DISTANCE_09172005_0721
   9
  10 #include <boost/fusion/iterator/detail/distance.hpp>
  11 #include <boost/fusion/support/category_of.hpp>
  12
  13 #include <boost/mpl/int.hpp>
  14 #include <boost/mpl/assert.hpp>
  15 #include <boost/type_traits/is_same.hpp>
  16
  17 #include <boost/fusion/support/tag_of.hpp>
  18
  19 namespace boost { namespace fusion
  20 {
  21     struct random_access_traversal_tag;
  22
  23     // Special tags:
  24     struct iterator_facade_tag; // iterator facade tag
  25     struct array_iterator_tag; // boost::array iterator tag
  26     struct mpl_iterator_tag; // mpl sequence iterator tag
  27     struct std_pair_iterator_tag; // std::pair iterator tag
  28
  29     namespace extension
  30     {
  31         template <typename Tag>
  32         struct distance_impl
  33         {
  34             // default implementation
  35             template <typename First, typename Last>
  36             struct apply : distance_detail::linear_distance<First, Last>
  37             {
  38                 BOOST_MPL_ASSERT_NOT((traits::is_random_access<First>));
  39                 BOOST_MPL_ASSERT_NOT((traits::is_random_access<Last>));
  40             };
  41         };
  42
  43         template <>
  44         struct distance_impl<iterator_facade_tag>
  45         {
  46             template <typename First, typename Last>
  47             struct apply : First::template distance<First, Last> {};
  48         };
  49
  50         template <>
  51         struct distance_impl<array_iterator_tag>;
  52
  53         template <>
  54         struct distance_impl<mpl_iterator_tag>;
  55
  56         template <>
  57         struct distance_impl<std_pair_iterator_tag>;
  58     }
  59
  60     namespace result_of
  61     {
  62         template <typename First, typename Last>
  63         struct distance
  64         : extension::distance_impl<typename detail::tag_of<First>::type>::
  65         template apply<First, Last>
  66         {
  67             typedef typename extension::distance_impl<typename detail::tag_of<First>::type>::
  68             template apply<First, Last>::type distance_application;
  69             BOOST_STATIC_CONSTANT(int, value = distance_application::value);
  70         };
  71     }
  72
  73     template <typename First, typename Last>
  74     inline typename result_of::distance<First, Last>::type
  75     distance(First const& a, Last const& b)
  76     {
  77         return result_of::distance<First, Last>::call(a,b);
  78     }
  79 }}
  80
  81 #endif