60 lines
1.5 KiB
C++
60 lines
1.5 KiB
C++
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#ifndef BOOST_METAPARSE_V1_ACCEPT_WHEN_HPP
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#define BOOST_METAPARSE_V1_ACCEPT_WHEN_HPP
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// Copyright Abel Sinkovics (abel@sinkovics.hu) 2009 - 2010.
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// Distributed under the Boost Software License, Version 1.0.
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// (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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#include <boost/metaparse/v1/get_result.hpp>
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#include <boost/metaparse/v1/reject.hpp>
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#include <boost/metaparse/v1/is_error.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/mpl/eval_if.hpp>
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namespace boost
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{
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namespace metaparse
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{
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namespace v1
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{
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template <class P, class Pred, class Msg>
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struct accept_when
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{
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private:
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struct unchecked
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{
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template <class S, class Pos>
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struct apply :
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boost::mpl::eval_if<
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typename Pred::template apply<
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typename get_result<typename P::template apply<S, Pos> >::type
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>::type,
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typename P::template apply<S, Pos>,
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reject<Msg, Pos>
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>
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{};
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};
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public:
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typedef accept_when type;
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template <class S, class Pos>
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struct apply :
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boost::mpl::if_<
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is_error<typename P::template apply<S, Pos> >,
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P,
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unchecked
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>::type::template apply<
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S,
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Pos
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>
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{};
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};
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}
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}
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}
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#endif
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