forked from boostorg/fusion
53 lines
1.5 KiB
C++
53 lines
1.5 KiB
C++
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/*=============================================================================
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Copyright (c) 2001-2006 Joel de Guzman
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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_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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struct fusion_sequence_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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}
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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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static 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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