list/detail/deref_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_DEREF_IMPL_07172005_0831)
0009 #define FUSION_DEREF_IMPL_07172005_0831
0010
0011 #include <boost/fusion/support/config.hpp>
0012 #include <boost/mpl/eval_if.hpp>
0013 #include <boost/type_traits/is_const.hpp>
0014 #include <boost/type_traits/add_const.hpp>
0015 #include <boost/type_traits/add_reference.hpp>
0016
0017 namespace boost { namespace fusion
0018 {
0019     struct cons_iterator_tag;
0020
0021     namespace extension
0022     {
0023         template <typename Tag>
0024         struct deref_impl;
0025
0026         template <>
0027         struct deref_impl<cons_iterator_tag>
0028         {
0029             template <typename Iterator>
0030             struct apply
0031             {
0032                 typedef typename Iterator::cons_type cons_type;
0033                 typedef typename cons_type::car_type value_type;
0034
0035                 typedef typename mpl::eval_if<
0036                     is_const<cons_type>
0037                   , add_reference<typename add_const<value_type>::type>
0038                   , add_reference<value_type> >::type
0039                 type;
0040
0041                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
0042                 static type
0043                 call(Iterator const& i)
0044                 {
0045                     return i.cons.car;
0046                 }
0047             };
0048         };
0049     }
0050 }}
0051
0052 #endif
0053
0054