| /*============================================================================= |
| 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(BOOST_FUSION_AT_KEY_20060304_1755) |
| #define BOOST_FUSION_AT_KEY_20060304_1755 |
| |
| #include <boost/type_traits/is_const.hpp> |
| #include <boost/fusion/algorithm/query/find.hpp> |
| #include <boost/fusion/iterator/deref_data.hpp> |
| #include <boost/fusion/support/tag_of.hpp> |
| #include <boost/fusion/support/detail/access.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 at_key_impl |
| { |
| template <typename Seq, typename Key> |
| struct apply |
| { |
| typedef typename |
| result_of::deref_data< |
| typename result_of::find<Seq, Key>::type |
| >::type |
| type; |
| |
| static type |
| call(Seq& seq) |
| { |
| return fusion::deref_data(fusion::find<Key>(seq)); |
| } |
| }; |
| }; |
| |
| template <> |
| struct at_key_impl<sequence_facade_tag> |
| { |
| template <typename Sequence, typename Key> |
| struct apply : Sequence::template at_key_impl<Sequence, Key> {}; |
| }; |
| |
| template <> |
| struct at_key_impl<boost_array_tag>; |
| |
| template <> |
| struct at_key_impl<mpl_sequence_tag>; |
| |
| template <> |
| struct at_key_impl<std_pair_tag>; |
| } |
| |
| namespace result_of |
| { |
| template <typename Sequence, typename Key> |
| struct at_key |
| : extension::at_key_impl<typename detail::tag_of<Sequence>::type>:: |
| template apply<Sequence, Key> |
| {}; |
| } |
| |
| template <typename Key, typename Sequence> |
| inline typename |
| lazy_disable_if< |
| is_const<Sequence> |
| , result_of::at_key<Sequence, Key> |
| >::type |
| at_key(Sequence& seq) |
| { |
| return result_of::at_key<Sequence, Key>::call(seq); |
| } |
| |
| template <typename Key, typename Sequence> |
| inline typename result_of::at_key<Sequence const, Key>::type |
| at_key(Sequence const& seq) |
| { |
| return result_of::at_key<Sequence const, Key>::call(seq); |
| } |
| }} |
| |
| #endif |