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_NEXT_IMPL_07172005_0836)
9 #define FUSION_NEXT_IMPL_07172005_0836
10 
11 #include <boost/fusion/support/config.hpp>
12 #include <boost/fusion/iterator/next.hpp>
13 #include <boost/fusion/iterator/equal_to.hpp>
14 #include <boost/mpl/eval_if.hpp>
15 #include <boost/mpl/identity.hpp>
16 #include <boost/type_traits/is_const.hpp>
17 #include <boost/type_traits/add_const.hpp>
18 
19 namespace boost { namespace fusion
20 {
21     struct cons_iterator_tag;
22 
23     template <typename Cons>
24     struct cons_iterator;
25 
26     namespace extension
27     {
28         template <typename Tag>
29         struct next_impl;
30 
31         template <>
32         struct next_impl<cons_iterator_tag>
33         {
34             template <typename Iterator>
35             struct apply
36             {
37                 typedef typename Iterator::cons_type cons_type;
38                 typedef typename cons_type::cdr_type cdr_type;
39 
40                 typedef cons_iterator<
41                     typename mpl::eval_if<
42                         is_const<cons_type>
43                       , add_const<cdr_type>
44                       , mpl::identity<cdr_type>
45                     >::type>
46                 type;
47 
48                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
49                 static type
callboost::fusion::extension::next_impl::apply50                 call(Iterator const& i)
51                 {
52                     return type(i.cons.cdr);
53                 }
54             };
55         };
56     }
57 }}
58 
59 #endif
60 
61 
62