66 lines
2.3 KiB
Plaintext
66 lines
2.3 KiB
Plaintext
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///////////////////////////////////////////////////////////////////////////////
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/// \file pop_front.hpp
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/// Proto callables Fusion pop_front
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//
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// Copyright 2010 Eric Niebler. Distributed under the Boost
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// Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_PROTO_FUNCTIONAL_FUSION_POP_FRONT_HPP_EAN_11_27_2010
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#define BOOST_PROTO_FUNCTIONAL_FUSION_POP_FRONT_HPP_EAN_11_27_2010
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#include <boost/fusion/include/begin.hpp>
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#include <boost/fusion/include/end.hpp>
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#include <boost/fusion/include/next.hpp>
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#include <boost/fusion/include/pop_front.hpp>
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#include <boost/proto/proto_fwd.hpp>
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namespace boost { namespace proto { namespace functional
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{
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/// \brief A PolymorphicFunctionObject type that invokes the
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/// \c fusion::pop_front() algorithm on its argument.
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///
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/// A PolymorphicFunctionObject type that invokes the
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/// \c fusion::pop_front() algorithm on its argument. This is
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/// useful for defining a CallableTransform like \c pop_front(_)
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/// which removes the first child from a Proto expression node.
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/// Such a transform might be used as the first argument to the
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/// \c proto::fold\<\> transform; that is, fold all but
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/// the first child.
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struct pop_front
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{
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BOOST_PROTO_CALLABLE()
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template<typename Sig>
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struct result;
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template<typename This, typename Seq>
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struct result<This(Seq)>
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: result<This(Seq const &)>
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{};
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template<typename This, typename Seq>
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struct result<This(Seq &)>
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: fusion::result_of::pop_front<Seq>
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{};
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template<typename Seq>
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typename fusion::result_of::pop_front<Seq>::type
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operator ()(Seq &seq) const
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{
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// Work around a const-correctness issue in Fusion
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typedef typename fusion::result_of::pop_front<Seq>::type result_type;
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return result_type(fusion::next(fusion::begin(seq)), fusion::end(seq));
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}
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template<typename Seq>
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typename fusion::result_of::pop_front<Seq const>::type
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operator ()(Seq const &seq) const
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{
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return fusion::pop_front(seq);
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}
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};
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}}}
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#endif
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