forked from boostorg/fusion
73 lines
2.0 KiB
C++
73 lines
2.0 KiB
C++
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/*=============================================================================
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Copyright (c) 2001-2006 Joel de Guzman
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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_HAS_KEY_09232005_1454)
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#define FUSION_HAS_KEY_09232005_1454
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#include <boost/mpl/not.hpp>
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#include <boost/fusion/support/tag_of.hpp>
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#include <boost/type_traits/is_same.hpp>
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namespace boost { namespace fusion
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{
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struct void_;
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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 has_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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: mpl::not_<is_same<typename Sequence::
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template meta_at_impl<Key>::type, void_> >
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{};
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};
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template <>
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struct has_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 has_key<Sequence, Key> {};
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};
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template <>
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struct has_key_impl<array_tag>;
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template <>
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struct has_key_impl<mpl_sequence_tag>;
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template <>
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struct has_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 Key>
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struct has_key
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: extension::has_key_impl<typename detail::tag_of<Sequence>::type>::
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template apply<Sequence, Key>
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{};
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}
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template <typename Key, typename Sequence>
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inline typename result_of::has_key<Sequence, Key>::type
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has_key(Sequence const& seq)
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{
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typedef typename result_of::has_key<Sequence, Key>::type result;
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return result();
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}
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}}
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#endif
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