boost/fusion/iterator/prior.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_PRIOR_05042005_1144)
   8 #define FUSION_PRIOR_05042005_1144
   9
  10 #include <boost/fusion/support/tag_of.hpp>
  11
  12 namespace boost { namespace fusion
  13 {
  14     // Special tags:
  15     struct iterator_facade_tag; // iterator facade tag
  16     struct array_iterator_tag; // boost::array iterator tag
  17     struct mpl_iterator_tag; // mpl sequence iterator tag
  18     struct std_pair_iterator_tag; // std::pair iterator tag
  19
  20     namespace extension
  21     {
  22         template <typename Tag>
  23         struct prior_impl
  24         {
  25             template <typename Iterator>
  26             struct apply {};
  27         };
  28
  29         template <>
  30         struct prior_impl<iterator_facade_tag>
  31         {
  32             template <typename Iterator>
  33             struct apply : Iterator::template prior<Iterator> {};
  34         };
  35
  36         template <>
  37         struct prior_impl<array_iterator_tag>;
  38
  39         template <>
  40         struct prior_impl<mpl_iterator_tag>;
  41
  42         template <>
  43         struct prior_impl<std_pair_iterator_tag>;
  44     }
  45
  46     namespace result_of
  47     {
  48         template <typename Iterator>
  49         struct prior
  50             : extension::prior_impl<typename detail::tag_of<Iterator>::type>::
  51                 template apply<Iterator>
  52         {};
  53     }
  54
  55     template <typename Iterator>
  56     typename result_of::prior<Iterator>::type const
  57     prior(Iterator const& i)
  58     {
  59         return result_of::prior<Iterator>::call(i);
  60     }
  61 }}
  62
  63 #endif