boost/fusion/container/map/detail/begin_impl.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_BEGIN_IMPL_05222005_1108)
   8 #define FUSION_BEGIN_IMPL_05222005_1108
   9
  10 #include <boost/fusion/sequence/intrinsic/begin.hpp>
  11 #include <boost/type_traits/is_const.hpp>
  12 #include <boost/mpl/eval_if.hpp>
  13 #include <boost/mpl/identity.hpp>
  14
  15 namespace boost { namespace fusion
  16 {
  17     struct map_tag;
  18
  19     namespace extension
  20     {
  21         template <typename Tag>
  22         struct begin_impl;
  23
  24         template <>
  25         struct begin_impl<map_tag>
  26         {
  27             template <typename Sequence>
  28             struct apply
  29             {
  30                 typedef typename
  31                     result_of::begin<typename Sequence::storage_type>::type
  32                 iterator_type;
  33
  34                 typedef typename
  35                     result_of::begin<typename Sequence::storage_type const>::type
  36                 const_iterator_type;
  37
  38                 typedef typename
  39                     mpl::eval_if<
  40                         is_const<Sequence>
  41                       , mpl::identity<const_iterator_type>
  42                       , mpl::identity<iterator_type>
  43                     >::type
  44                 type;
  45
  46                 static type
  47                 call(Sequence& m)
  48                 {
  49                     return fusion::begin(m.get_data());
  50                 }
  51             };
  52         };
  53     }
  54 }}
  55
  56 #endif