Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: /// \file pop_front.hpp
Chris@16: /// Proto callables Fusion pop_front
Chris@16: //
Chris@16: //  Copyright 2010 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_PROTO_FUNCTIONAL_FUSION_POP_FRONT_HPP_EAN_11_27_2010
Chris@16: #define BOOST_PROTO_FUNCTIONAL_FUSION_POP_FRONT_HPP_EAN_11_27_2010
Chris@16: 
Chris@16: #include <boost/fusion/include/begin.hpp>
Chris@16: #include <boost/fusion/include/end.hpp>
Chris@16: #include <boost/fusion/include/next.hpp>
Chris@16: #include <boost/fusion/include/pop_front.hpp>
Chris@16: #include <boost/proto/proto_fwd.hpp>
Chris@16: 
Chris@16: namespace boost { namespace proto { namespace functional
Chris@16: {
Chris@16:     /// \brief A PolymorphicFunctionObject type that invokes the
Chris@16:     /// \c fusion::pop_front() algorithm on its argument.
Chris@16:     ///
Chris@16:     /// A PolymorphicFunctionObject type that invokes the
Chris@16:     /// \c fusion::pop_front() algorithm on its argument. This is
Chris@16:     /// useful for defining a CallableTransform like \c pop_front(_)
Chris@16:     /// which removes the first child from a Proto expression node.
Chris@16:     /// Such a transform might be used as the first argument to the
Chris@16:     /// \c proto::fold\<\> transform; that is, fold all but
Chris@16:     /// the first child.
Chris@16:     struct pop_front
Chris@16:     {
Chris@16:         BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:         template<typename Sig>
Chris@16:         struct result;
Chris@16: 
Chris@16:         template<typename This, typename Seq>
Chris@16:         struct result<This(Seq)>
Chris@16:           : result<This(Seq const &)>
Chris@16:         {};
Chris@16: 
Chris@16:         template<typename This, typename Seq>
Chris@16:         struct result<This(Seq &)>
Chris@16:           : fusion::result_of::pop_front<Seq>
Chris@16:         {};
Chris@16: 
Chris@16:         template<typename Seq>
Chris@16:         typename fusion::result_of::pop_front<Seq>::type
Chris@16:         operator ()(Seq &seq) const
Chris@16:         {
Chris@16:             // Work around a const-correctness issue in Fusion
Chris@16:             typedef typename fusion::result_of::pop_front<Seq>::type result_type;
Chris@16:             return result_type(fusion::next(fusion::begin(seq)), fusion::end(seq));
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Seq>
Chris@16:         typename fusion::result_of::pop_front<Seq const>::type
Chris@16:         operator ()(Seq const &seq) const
Chris@16:         {
Chris@16:             return fusion::pop_front(seq);
Chris@16:         }
Chris@16:     };
Chris@16: }}}
Chris@16: 
Chris@16: #endif