// Copyright David Abrahams 2006. 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_DETAIL_FUNCTION1_DWA200655_HPP | |
# define BOOST_DETAIL_FUNCTION1_DWA200655_HPP | |
# include <boost/concept_check.hpp> | |
# include <boost/type_traits/remove_reference.hpp> | |
# include <boost/type_traits/add_const.hpp> | |
# include <boost/mpl/apply.hpp> | |
namespace boost { namespace detail { | |
// A utility for creating unary function objects that play nicely with | |
// boost::result_of and that handle the forwarding problem. | |
// | |
// mpl::apply<F, A0>::type is expected to be a stateless function | |
// object that accepts an argument of type A0&. It is also expected | |
// to have a nested ::result_type identical to its return type. | |
template<typename F> | |
struct function1 | |
{ | |
template<typename Signature> | |
struct result | |
{}; | |
template<typename This, typename A0> | |
struct result<This(A0)> | |
{ | |
// How adding const to arguments handles rvalues. | |
// | |
// if A0 is arg0 is represents actual argument | |
// -------- ------- -------------------------- | |
// T const & T const const T lvalue | |
// T & T non-const T lvalue | |
// T const T const const T rvalue | |
// T T const non-const T rvalue | |
typedef typename remove_reference< | |
typename add_const< A0 >::type | |
>::type arg0; | |
typedef typename mpl::apply1<F, arg0>::type impl; | |
typedef typename impl::result_type type; | |
}; | |
// Handles mutable lvalues | |
template<typename A0> | |
typename result<function1(A0 &)>::type | |
operator ()(A0 &a0) const | |
{ | |
typedef typename result<function1(A0 &)>::impl impl; | |
typedef typename result<function1(A0 &)>::type type; | |
typedef A0 &arg0; | |
BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); | |
//boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); | |
return impl()(a0); | |
} | |
// Handles const lvalues and all rvalues | |
template<typename A0> | |
typename result<function1(A0 const &)>::type | |
operator ()(A0 const &a0) const | |
{ | |
typedef typename result<function1(A0 const &)>::impl impl; | |
typedef typename result<function1(A0 const &)>::type type; | |
typedef A0 const &arg0; | |
BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); | |
//boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); | |
return impl()(a0); | |
} | |
}; | |
}} // namespace boost::detail | |
#endif // BOOST_DETAIL_FUNCTION1_DWA200655_HPP |