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66 lines
1.9 KiB
66 lines
1.9 KiB
/*============================================================================= |
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Copyright (c) 2001-2011 Joel de Guzman |
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Copyright (c) 2006 Dan Marsden |
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Distributed under the Boost Software License, Version 1.0. (See accompanying |
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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==============================================================================*/ |
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#if !defined(FUSION_VALUE_AT_KEY_05052005_0229) |
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#define FUSION_VALUE_AT_KEY_05052005_0229 |
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#include <boost/mpl/int.hpp> |
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#include <boost/fusion/sequence/intrinsic_fwd.hpp> |
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#include <boost/fusion/iterator/value_of_data.hpp> |
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#include <boost/fusion/algorithm/query/find.hpp> |
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#include <boost/fusion/support/tag_of.hpp> |
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namespace boost { namespace fusion |
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{ |
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// Special tags: |
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struct sequence_facade_tag; |
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struct boost_array_tag; // boost::array tag |
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struct mpl_sequence_tag; // mpl sequence tag |
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struct std_pair_tag; // std::pair tag |
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namespace extension |
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{ |
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template <typename Tag> |
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struct value_at_key_impl |
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{ |
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template <typename Seq, typename Key> |
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struct apply |
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: result_of::value_of_data< |
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typename result_of::find<Seq, Key>::type |
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> |
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{}; |
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}; |
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template <> |
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struct value_at_key_impl<sequence_facade_tag> |
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{ |
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template <typename Sequence, typename Key> |
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struct apply : Sequence::template value_at_key<Sequence, Key> {}; |
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}; |
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template <> |
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struct value_at_key_impl<boost_array_tag>; |
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template <> |
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struct value_at_key_impl<mpl_sequence_tag>; |
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template <> |
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struct value_at_key_impl<std_pair_tag>; |
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} |
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namespace result_of |
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{ |
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template <typename Sequence, typename N> |
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struct value_at_key |
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: extension::value_at_key_impl<typename detail::tag_of<Sequence>::type>:: |
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template apply<Sequence, N> |
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{}; |
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} |
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}} |
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#endif |
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