boost/fusion/container/list/detail/deref_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_DEREF_IMPL_07172005_0831)
   9 #define FUSION_DEREF_IMPL_07172005_0831
  10
  11 #include <boost/mpl/eval_if.hpp>
  12 #include <boost/type_traits/is_const.hpp>
  13 #include <boost/type_traits/add_const.hpp>
  14 #include <boost/type_traits/add_reference.hpp>
  15
  16 namespace boost { namespace fusion
  17 {
  18     struct cons_iterator_tag;
  19
  20     namespace extension
  21     {
  22         template <typename Tag>
  23         struct deref_impl;
  24
  25         template <>
  26         struct deref_impl<cons_iterator_tag>
  27         {
  28             template <typename Iterator>
  29             struct apply
  30             {
  31                 typedef typename Iterator::cons_type cons_type;
  32                 typedef typename cons_type::car_type value_type;
  33
  34                 typedef typename mpl::eval_if<
  35                     is_const<cons_type>
  36                   , add_reference<typename add_const<value_type>::type>
  37                   , add_reference<value_type> >::type
  38                 type;
  39
  40                 static type
  41                 call(Iterator const& i)
  42                 {
  43                     return i.cons.car;
  44                 }
  45             };
  46         };
  47     }
  48 }}
  49
  50 #endif
  51
  52