1 /////////////////////////////////////////////////////////////////////////////// 2 /// \file pop_back.hpp 3 /// Proto callables Fusion pop_back 4 // 5 // Copyright 2010 Eric Niebler. Distributed under the Boost 6 // Software License, Version 1.0. (See accompanying file 7 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 8 9 #ifndef BOOST_PROTO_FUNCTIONAL_FUSION_POP_BACK_HPP_EAN_11_27_2010 10 #define BOOST_PROTO_FUNCTIONAL_FUSION_POP_BACK_HPP_EAN_11_27_2010 11 12 #include <boost/fusion/include/begin.hpp> 13 #include <boost/fusion/include/end.hpp> 14 #include <boost/fusion/include/prior.hpp> 15 #include <boost/fusion/include/pop_back.hpp> 16 #include <boost/proto/proto_fwd.hpp> 17 18 namespace boost { namespace proto { namespace functional 19 { 20 /// \brief A PolymorphicFunctionObject type that invokes the 21 /// \c fusion::pop_back() algorithm on its argument. 22 /// 23 /// A PolymorphicFunctionObject type that invokes the 24 /// \c fusion::pop_back() algorithm on its argument. 25 struct pop_back 26 { 27 BOOST_PROTO_CALLABLE() 28 29 template<typename Sig> 30 struct result; 31 32 template<typename This, typename Seq> 33 struct result<This(Seq)> 34 : result<This(Seq const &)> 35 {}; 36 37 template<typename This, typename Seq> 38 struct result<This(Seq &)> 39 : fusion::result_of::pop_back<Seq> 40 {}; 41 42 template<typename Seq> 43 typename fusion::result_of::pop_back<Seq>::type operator ()boost::proto::functional::pop_back44 operator ()(Seq &seq) const 45 { 46 // Work around a const-correctness issue in Fusion 47 typedef typename fusion::result_of::pop_back<Seq>::type result_type; 48 return result_type(fusion::begin(seq), fusion::prior(fusion::end(seq))); 49 } 50 51 template<typename Seq> 52 typename fusion::result_of::pop_back<Seq const>::type operator ()boost::proto::functional::pop_back53 operator ()(Seq const &seq) const 54 { 55 return fusion::pop_back(seq); 56 } 57 }; 58 }}} 59 60 #endif 61