list/detail/next_impl.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
0003     Copyright (c) 2005 Eric Niebler
0004
0005     Distributed under the Boost Software License, Version 1.0. (See accompanying
0006     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007 ==============================================================================*/
0008 #if !defined(FUSION_NEXT_IMPL_07172005_0836)
0009 #define FUSION_NEXT_IMPL_07172005_0836
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/fusion/iterator/next.hpp>
0013 #include <boost/fusion/iterator/equal_to.hpp>
0014 #include <boost/mpl/eval_if.hpp>
0015 #include <boost/mpl/identity.hpp>
0016 #include <boost/type_traits/is_const.hpp>
0017 #include <boost/type_traits/add_const.hpp>
0018
0019 namespace boost { namespace fusion
0020 {
0021     struct cons_iterator_tag;
0022
0023     template <typename Cons>
0024     struct cons_iterator;
0025
0026     namespace extension
0027     {
0028         template <typename Tag>
0029         struct next_impl;
0030
0031         template <>
0032         struct next_impl<cons_iterator_tag>
0033         {
0034             template <typename Iterator>
0035             struct apply
0036             {
0037                 typedef typename Iterator::cons_type cons_type;
0038                 typedef typename cons_type::cdr_type cdr_type;
0039
0040                 typedef cons_iterator<
0041                     typename mpl::eval_if<
0042                         is_const<cons_type>
0043                       , add_const<cdr_type>
0044                       , mpl::identity<cdr_type>
0045                     >::type>
0046                 type;
0047
0048                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0049                 static type
0050                 call(Iterator const& i)
0051                 {
0052                     return type(i.cons.cdr);
0053                 }
0054             };
0055         };
0056     }
0057 }}
0058
0059 #endif
0060
0061