| /*============================================================================= |
| Copyright (c) 2001-2006 Joel de Guzman |
| Copyright (c) 2006 Dan Marsden |
| |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| ==============================================================================*/ |
| #if !defined(FUSION_VALUE_AT_KEY_05052005_0229) |
| #define FUSION_VALUE_AT_KEY_05052005_0229 |
| |
| #include <boost/mpl/int.hpp> |
| #include <boost/fusion/iterator/value_of_data.hpp> |
| #include <boost/fusion/algorithm/query/find.hpp> |
| #include <boost/fusion/support/tag_of.hpp> |
| |
| namespace boost { namespace fusion |
| { |
| // Special tags: |
| struct sequence_facade_tag; |
| struct boost_array_tag; // boost::array tag |
| struct mpl_sequence_tag; // mpl sequence tag |
| struct std_pair_tag; // std::pair tag |
| |
| namespace extension |
| { |
| template <typename Tag> |
| struct value_at_key_impl |
| { |
| template <typename Seq, typename Key> |
| struct apply |
| : result_of::value_of_data< |
| typename result_of::find<Seq, Key>::type |
| > |
| {}; |
| }; |
| |
| template <> |
| struct value_at_key_impl<sequence_facade_tag> |
| { |
| template <typename Sequence, typename Key> |
| struct apply : Sequence::template value_at_key<Sequence, Key> {}; |
| }; |
| |
| template <> |
| struct value_at_key_impl<boost_array_tag>; |
| |
| template <> |
| struct value_at_key_impl<mpl_sequence_tag>; |
| |
| template <> |
| struct value_at_key_impl<std_pair_tag>; |
| } |
| |
| namespace result_of |
| { |
| template <typename Sequence, typename N> |
| struct value_at_key |
| : extension::value_at_key_impl<typename detail::tag_of<Sequence>::type>:: |
| template apply<Sequence, N> |
| {}; |
| } |
| }} |
| |
| #endif |
| |