1 /*=============================================================================
2     Copyright (c) 2001-2011 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/fusion/support/config.hpp>
12 #include <boost/mpl/eval_if.hpp>
13 #include <boost/type_traits/is_const.hpp>
14 #include <boost/type_traits/add_const.hpp>
15 #include <boost/type_traits/add_reference.hpp>
16 
17 namespace boost { namespace fusion
18 {
19     struct cons_iterator_tag;
20 
21     namespace extension
22     {
23         template <typename Tag>
24         struct deref_impl;
25 
26         template <>
27         struct deref_impl<cons_iterator_tag>
28         {
29             template <typename Iterator>
30             struct apply
31             {
32                 typedef typename Iterator::cons_type cons_type;
33                 typedef typename cons_type::car_type value_type;
34 
35                 typedef typename mpl::eval_if<
36                     is_const<cons_type>
37                   , add_reference<typename add_const<value_type>::type>
38                   , add_reference<value_type> >::type
39                 type;
40 
41                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
42                 static type
callboost::fusion::extension::deref_impl::apply43                 call(Iterator const& i)
44                 {
45                     return i.cons.car;
46                 }
47             };
48         };
49     }
50 }}
51 
52 #endif
53 
54 
55