fusion/support/is_view.hpp

0001 /*=============================================================================
0002     Copyright (c) 2001-2011 Joel de Guzman
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(FUSION_IS_VIEW_03202006_0015)
0008 #define FUSION_IS_VIEW_03202006_0015
0009
0010 #include <boost/fusion/support/config.hpp>
0011 #include <boost/mpl/bool.hpp>
0012 #include <boost/fusion/support/tag_of.hpp>
0013
0014 namespace boost { namespace fusion
0015 {
0016     // Special tags:
0017     struct non_fusion_tag;
0018     struct sequence_facade_tag;
0019     struct boost_tuple_tag; // boost::tuples::tuple tag
0020     struct boost_array_tag; // boost::array tag
0021     struct mpl_sequence_tag; // mpl sequence tag
0022     struct std_pair_tag; // std::pair tag
0023
0024     namespace extension
0025     {
0026         template<typename Tag>
0027         struct is_view_impl
0028         {
0029             template <typename T>
0030             struct apply
0031             {
0032                 typedef typename T::is_view type;
0033             };
0034         };
0035
0036         template <>
0037         struct is_view_impl<non_fusion_tag>
0038         {
0039             template <typename T>
0040             struct apply : mpl::false_ {};
0041         };
0042
0043         template <>
0044         struct is_view_impl<sequence_facade_tag>
0045         {
0046             template <typename Sequence>
0047             struct apply : Sequence::is_view {};
0048         };
0049
0050         template <>
0051         struct is_view_impl<boost_tuple_tag>;
0052
0053         template <>
0054         struct is_view_impl<boost_array_tag>;
0055
0056         template <>
0057         struct is_view_impl<mpl_sequence_tag>;
0058
0059         template <>
0060         struct is_view_impl<std_pair_tag>;
0061     }
0062
0063     namespace traits
0064     {
0065         template <typename T>
0066         struct is_view :
0067             mpl::bool_<
0068                 (bool)extension::is_view_impl<typename fusion::detail::tag_of<T>::type>::
0069                     template apply<T>::type::value
0070             >
0071         {};
0072     }
0073 }}
0074
0075 #endif