| /*============================================================================= |
| Copyright (c) 2001-2006 Joel de Guzman |
| |
| 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_AT_KEY_IMPL_09162005_1118) |
| #define FUSION_AT_KEY_IMPL_09162005_1118 |
| |
| #include <boost/fusion/support/detail/access.hpp> |
| #include <boost/type_traits/is_const.hpp> |
| #include <boost/mpl/identity.hpp> |
| |
| namespace boost { namespace fusion |
| { |
| struct set_tag; |
| |
| namespace extension |
| { |
| template <typename Tag> |
| struct at_key_impl; |
| |
| template <> |
| struct at_key_impl<set_tag> |
| { |
| template <typename Sequence, typename Key> |
| struct apply |
| { |
| typedef typename Sequence::template meta_at_impl<Key> element; |
| |
| typedef typename |
| mpl::eval_if< |
| is_const<Sequence> |
| , detail::cref_result<element> |
| , detail::ref_result<element> |
| >::type |
| type; |
| |
| static type |
| call(Sequence& s) |
| { |
| return s.at_impl(mpl::identity<Key>()); |
| } |
| }; |
| }; |
| } |
| }} |
| |
| #endif |