//----------------------------------------------------------------------------- // boost variant/visitor_ptr.hpp header file // See http://www.boost.org for updates, documentation, and revision history. //----------------------------------------------------------------------------- // // Copyright (c) 2002-2003 // Eric Friedman // // 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_VARIANT_VISITOR_PTR_HPP #define BOOST_VARIANT_VISITOR_PTR_HPP #include "boost/variant/bad_visit.hpp" #include "boost/variant/static_visitor.hpp" #include "boost/mpl/eval_if.hpp" #include "boost/mpl/identity.hpp" #include "boost/type_traits/add_reference.hpp" #include "boost/type_traits/is_reference.hpp" #include "boost/type_traits/is_void.hpp" namespace boost { ////////////////////////////////////////////////////////////////////////// // function template visitor_ptr // // Adapts a function pointer for use as visitor capable of handling // values of a single type. Throws bad_visit if inappropriately applied. // template <typename T, typename R> class visitor_ptr_t : public static_visitor<R> { private: // representation typedef R (*visitor_t)(T); visitor_t visitor_; public: // typedefs typedef R result_type; private: // private typedefs typedef typename mpl::eval_if< is_reference<T> , mpl::identity<T> , add_reference<const T> >::type argument_fwd_type; public: // structors explicit visitor_ptr_t(visitor_t visitor) : visitor_(visitor) { } public: // static visitor interfaces template <typename U> result_type operator()(const U&) const { throw bad_visit(); } #if !defined(BOOST_NO_VOID_RETURNS) public: // static visitor interfaces, cont. result_type operator()(argument_fwd_type operand) const { return visitor_(operand); } #else // defined(BOOST_NO_VOID_RETURNS) private: // helpers, for static visitor interfaces (below) result_type execute_impl(argument_fwd_type operand, mpl::false_) const { return visitor_(operand); } BOOST_VARIANT_AUX_RETURN_VOID_TYPE execute_impl(argument_fwd_type operand, mpl::true_) const { visitor_(operand); BOOST_VARIANT_AUX_RETURN_VOID; } public: // static visitor interfaces, cont. BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) operator()(argument_fwd_type operand) const { typedef typename is_void<result_type>::type has_void_result; return execute_impl(operand, has_void_result()); } #endif // BOOST_NO_VOID_RETURNS workaround }; template <typename R, typename T> inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T)) { return visitor_ptr_t<T,R>(visitor); } } // namespace boost #endif// BOOST_VISITOR_VISITOR_PTR_HPP