list/detail/empty_impl.hpp

0001 /*=============================================================================
0002     Copyright (c) 2007 Tobias Schwinger
0003
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 ==============================================================================*/
0007 #if !defined(BOOST_FUSION_SEQUENCE_EMPTY_IMPL_HPP_INCLUDED)
0008 #define BOOST_FUSION_SEQUENCE_EMPTY_IMPL_HPP_INCLUDED
0009
0010 #include <boost/fusion/support/config.hpp>
0011 #include <boost/type_traits/is_convertible.hpp>
0012 #include <boost/fusion/container/list/nil.hpp>
0013
0014 namespace boost { namespace fusion
0015 {
0016     struct cons_tag;
0017
0018     struct nil_;
0019
0020     template <typename Car, typename Cdr>
0021     struct cons;
0022
0023     namespace extension
0024     {
0025         template <typename Tag>
0026         struct empty_impl;
0027
0028         template <>
0029         struct empty_impl<cons_tag>
0030         {
0031             template <typename Sequence>
0032             struct apply
0033                 : boost::is_convertible<Sequence, nil_>
0034             {};
0035         };
0036     }
0037 }}
0038
0039 #endif