1 // Copyright David Abrahams 2006. Distributed under the Boost 2 // Software License, Version 1.0. (See accompanying 3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 4 #ifndef BOOST_DETAIL_FUNCTION1_DWA200655_HPP 5 # define BOOST_DETAIL_FUNCTION1_DWA200655_HPP 6 7 # include <boost/concept_check.hpp> 8 # include <boost/type_traits/remove_reference.hpp> 9 # include <boost/type_traits/add_const.hpp> 10 # include <boost/mpl/apply.hpp> 11 12 namespace boost { namespace detail { 13 14 // A utility for creating unary function objects that play nicely with 15 // boost::result_of and that handle the forwarding problem. 16 // 17 // mpl::apply<F, A0>::type is expected to be a stateless function 18 // object that accepts an argument of type A0&. It is also expected 19 // to have a nested ::result_type identical to its return type. 20 template<typename F> 21 struct function1 22 { 23 template<typename Signature> 24 struct result 25 {}; 26 27 template<typename This, typename A0> 28 struct result<This(A0)> 29 { 30 // How adding const to arguments handles rvalues. 31 // 32 // if A0 is arg0 is represents actual argument 33 // -------- ------- -------------------------- 34 // T const & T const const T lvalue 35 // T & T non-const T lvalue 36 // T const T const const T rvalue 37 // T T const non-const T rvalue 38 typedef typename remove_reference< 39 typename add_const< A0 >::type 40 >::type arg0; 41 42 typedef typename mpl::apply1<F, arg0>::type impl; 43 typedef typename impl::result_type type; 44 }; 45 46 // Handles mutable lvalues 47 template<typename A0> 48 typename result<function1(A0 &)>::type operator ()boost::detail::function149 operator ()(A0 &a0) const 50 { 51 typedef typename result<function1(A0 &)>::impl impl; 52 typedef typename result<function1(A0 &)>::type type; 53 typedef A0 &arg0; 54 BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); 55 //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); 56 return impl()(a0); 57 } 58 59 // Handles const lvalues and all rvalues 60 template<typename A0> 61 typename result<function1(A0 const &)>::type operator ()boost::detail::function162 operator ()(A0 const &a0) const 63 { 64 typedef typename result<function1(A0 const &)>::impl impl; 65 typedef typename result<function1(A0 const &)>::type type; 66 typedef A0 const &arg0; 67 BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); 68 //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); 69 return impl()(a0); 70 } 71 }; 72 73 }} // namespace boost::detail 74 75 #endif // BOOST_DETAIL_FUNCTION1_DWA200655_HPP 76