| /*============================================================================= |
| 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_EMPTY_09162005_0335) |
| #define FUSION_EMPTY_09162005_0335 |
| |
| #include <boost/fusion/sequence/intrinsic/size.hpp> |
| #include <boost/mpl/bool.hpp> |
| #include <boost/fusion/support/tag_of.hpp> |
| |
| namespace boost { namespace fusion |
| { |
| // Special tags: |
| struct sequence_facade_tag; |
| struct mpl_sequence_tag; // mpl sequence tag |
| |
| namespace extension |
| { |
| template <typename Tag> |
| struct empty_impl |
| { |
| template <typename Sequence> |
| struct apply |
| : mpl::bool_<(result_of::size<Sequence>::value == 0)> |
| {}; |
| }; |
| |
| template <> |
| struct empty_impl<sequence_facade_tag> |
| { |
| template <typename Sequence> |
| struct apply : Sequence::template empty<Sequence> {}; |
| }; |
| |
| template <> |
| struct empty_impl<mpl_sequence_tag>; |
| } |
| |
| namespace result_of |
| { |
| template <typename Sequence> |
| struct empty |
| : extension::empty_impl<typename detail::tag_of<Sequence>::type>:: |
| template apply<Sequence> |
| {}; |
| } |
| |
| template <typename Sequence> |
| inline typename result_of::empty<Sequence>::type |
| empty(Sequence const&) |
| { |
| typedef typename result_of::empty<Sequence>::type result; |
| return result(); |
| } |
| }} |
| |
| #endif |