forked from boostorg/fusion
61 lines
1.7 KiB
C++
61 lines
1.7 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2006 Joel de Guzman
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Copyright (c) 2006 Dan Marsden
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Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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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/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 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 Sequence, typename Key>
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struct apply;
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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<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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