boost/fusion/container/list/detail/next_impl.hpp

   1 /*=============================================================================
   2     Copyright (c) 2005 Joel de Guzman
   3     Copyright (c) 2005 Eric Niebler
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ==============================================================================*/
   8 #if !defined(FUSION_NEXT_IMPL_07172005_0836)
   9 #define FUSION_NEXT_IMPL_07172005_0836
  10
  11 #include <boost/fusion/iterator/next.hpp>
  12 #include <boost/fusion/iterator/equal_to.hpp>
  13 #include <boost/mpl/eval_if.hpp>
  14 #include <boost/mpl/identity.hpp>
  15 #include <boost/type_traits/is_const.hpp>
  16 #include <boost/type_traits/add_const.hpp>
  17
  18 namespace boost { namespace fusion
  19 {
  20     struct cons_iterator_tag;
  21
  22     template <typename Cons>
  23     struct cons_iterator;
  24
  25     namespace extension
  26     {
  27         template <typename Tag>
  28         struct next_impl;
  29
  30         template <>
  31         struct next_impl<cons_iterator_tag>
  32         {
  33             template <typename Iterator>
  34             struct apply
  35             {
  36                 typedef typename Iterator::cons_type cons_type;
  37                 typedef typename cons_type::cdr_type cdr_type;
  38
  39                 typedef cons_iterator<
  40                     typename mpl::eval_if<
  41                         is_const<cons_type>
  42                       , add_const<cdr_type>
  43                       , mpl::identity<cdr_type>
  44                     >::type>
  45                 type;
  46
  47                 static type
  48                 call(Iterator const& i)
  49                 {
  50                     return type(i.cons.cdr);
  51                 }
  52             };
  53         };
  54     }
  55 }}
  56
  57 #endif
  58
  59