// (C) Copyright Tobias Schwinger // // Use modification and distribution are subject to the boost Software License, // Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt). //------------------------------------------------------------------------------ // // Reimplementation of the Boost result_of utility (see [Gregor01] and // [Gregor02]). // // // Detailed description // ==================== // // This example implements the functionality of the Boost result_of utility. // Because of FunctionTypes we get away without repetitive code and the Boost // Preprocessor library. // // // Bibliography // ============ // // [Gregor01] Gregor, D. The Boost result_of utility // http://www.boost.org/libs/utility // // [Gregor02] Gregor, D. A uniform method for computing function object return // types (revision 1) // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1454.html #include <boost/function_types/result_type.hpp> #include <boost/function_types/is_callable_builtin.hpp> #include <boost/mpl/eval_if.hpp> #include <boost/mpl/has_xxx.hpp> namespace example { namespace ft = boost::function_types; namespace mpl = boost::mpl; template<typename F> struct result_of; namespace detail { BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type) template<typename F> struct result_type_member { typedef typename F::result_type type; }; template<typename F, typename Desc> struct result_member_template { typedef typename F::template result<Desc>::type type; }; #if !BOOST_WORKAROUND(__BORLANDC__,BOOST_TESTED_AT(0x564)) template<typename F> struct result_member_template< F, F(void) > { typedef void type; }; #endif template<typename F, typename Desc> struct result_of_impl : mpl::eval_if < ft::is_callable_builtin<F> , ft::result_type<F> , mpl::eval_if < has_result_type<F> , result_type_member<F> , result_member_template<F,Desc> > > { }; } template<typename Desc> struct result_of : detail::result_of_impl< typename ft::result_type<Desc>::type, Desc > { }; }