| // 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 |