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