/////////////////////////////////////////////////////////////////////////////// | |
/// \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 |