Chris@16: // Copyright David Abrahams 2006. Distributed under the Boost
Chris@16: // Software License, Version 1.0. (See accompanying
Chris@16: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: #ifndef BOOST_DETAIL_FUNCTION1_DWA200655_HPP
Chris@16: # define BOOST_DETAIL_FUNCTION1_DWA200655_HPP
Chris@16: 
Chris@16: # include <boost/concept_check.hpp>
Chris@16: # include <boost/type_traits/remove_reference.hpp>
Chris@16: # include <boost/type_traits/add_const.hpp>
Chris@16: # include <boost/mpl/apply.hpp>
Chris@16: 
Chris@16: namespace boost { namespace detail {
Chris@16: 
Chris@16: // A utility for creating unary function objects that play nicely with
Chris@16: // boost::result_of and that handle the forwarding problem.
Chris@16: //
Chris@16: // mpl::apply<F, A0>::type is expected to be a stateless function
Chris@16: // object that accepts an argument of type A0&.  It is also expected
Chris@16: // to have a nested ::result_type identical to its return type.
Chris@16: template<typename F>
Chris@16: struct function1
Chris@16: {
Chris@16:     template<typename Signature>
Chris@16:     struct result
Chris@16:     {};
Chris@16: 
Chris@16:     template<typename This, typename A0>
Chris@16:     struct result<This(A0)>
Chris@16:     {
Chris@16:         // How adding const to arguments handles rvalues.
Chris@16:         //
Chris@16:         // if A0 is     arg0 is       represents actual argument
Chris@16:         // --------     -------       --------------------------
Chris@16:         // T const &    T const       const T lvalue
Chris@16:         // T &          T             non-const T lvalue
Chris@16:         // T const      T const       const T rvalue
Chris@16:         // T            T const       non-const T rvalue
Chris@16:         typedef typename remove_reference<
Chris@16:             typename add_const< A0 >::type
Chris@16:         >::type arg0;
Chris@16: 
Chris@16:         typedef typename mpl::apply1<F, arg0>::type impl;
Chris@16:         typedef typename impl::result_type type;
Chris@16:     };
Chris@16: 
Chris@16:     // Handles mutable lvalues
Chris@16:     template<typename A0>
Chris@16:     typename result<function1(A0 &)>::type
Chris@16:     operator ()(A0 &a0) const
Chris@16:     {
Chris@16:         typedef typename result<function1(A0 &)>::impl impl;
Chris@16:         typedef typename result<function1(A0 &)>::type type;
Chris@16:         typedef A0 &arg0;
Chris@16:         BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>));
Chris@16:         //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >();
Chris@16:         return impl()(a0);
Chris@16:     }
Chris@16: 
Chris@16:     // Handles const lvalues and all rvalues
Chris@16:     template<typename A0>
Chris@16:     typename result<function1(A0 const &)>::type
Chris@16:     operator ()(A0 const &a0) const
Chris@16:     {
Chris@16:         typedef typename result<function1(A0 const &)>::impl impl;
Chris@16:         typedef typename result<function1(A0 const &)>::type type;
Chris@16:         typedef A0 const &arg0;
Chris@16:         BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>));
Chris@16:         //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >();
Chris@16:         return impl()(a0);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: }} // namespace boost::detail
Chris@16: 
Chris@16: #endif // BOOST_DETAIL_FUNCTION1_DWA200655_HPP