Chris@16: //-----------------------------------------------------------------------------
Chris@16: // boost variant/visitor_ptr.hpp header file
Chris@16: // See http://www.boost.org for updates, documentation, and revision history.
Chris@16: //-----------------------------------------------------------------------------
Chris@16: //
Chris@16: // Copyright (c) 2002-2003
Chris@16: // Eric Friedman
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_VARIANT_VISITOR_PTR_HPP
Chris@16: #define BOOST_VARIANT_VISITOR_PTR_HPP
Chris@16: 
Chris@16: #include "boost/variant/bad_visit.hpp"
Chris@16: #include "boost/variant/static_visitor.hpp"
Chris@16: 
Chris@16: #include "boost/mpl/eval_if.hpp"
Chris@16: #include "boost/mpl/identity.hpp"
Chris@16: #include "boost/throw_exception.hpp"
Chris@16: #include "boost/type_traits/add_reference.hpp"
Chris@16: #include "boost/type_traits/is_reference.hpp"
Chris@16: #include "boost/type_traits/is_void.hpp"
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //////////////////////////////////////////////////////////////////////////
Chris@16: // function template visitor_ptr
Chris@16: //
Chris@16: // Adapts a function pointer for use as visitor capable of handling
Chris@16: // values of a single type. Throws bad_visit if inappropriately applied.
Chris@16: //
Chris@16: template <typename T, typename R>
Chris@16: class visitor_ptr_t
Chris@16:     : public static_visitor<R>
Chris@16: {
Chris@16: private: // representation
Chris@16: 
Chris@16:     typedef R (*visitor_t)(T);
Chris@16: 
Chris@16:     visitor_t visitor_;
Chris@16: 
Chris@16: public: // typedefs
Chris@16: 
Chris@16:     typedef R result_type;
Chris@16: 
Chris@16: private: // private typedefs
Chris@16: 
Chris@16:     typedef typename mpl::eval_if<
Chris@16:           is_reference<T>
Chris@16:         , mpl::identity<T>
Chris@16:         , add_reference<const T>
Chris@16:         >::type argument_fwd_type;
Chris@16: 
Chris@16: public: // structors
Chris@16: 
Chris@101:     explicit visitor_ptr_t(visitor_t visitor) BOOST_NOEXCEPT
Chris@16:       : visitor_(visitor)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16: public: // static visitor interfaces
Chris@16: 
Chris@16:     template <typename U>
Chris@16:     result_type operator()(const U&) const
Chris@16:     {
Chris@16:         boost::throw_exception(bad_visit());
Chris@16:     }
Chris@16: 
Chris@16: #if !defined(BOOST_NO_VOID_RETURNS)
Chris@16: 
Chris@16: public: // static visitor interfaces, cont.
Chris@16: 
Chris@16:     result_type operator()(argument_fwd_type operand) const
Chris@16:     {
Chris@16:         return visitor_(operand);
Chris@16:     }
Chris@16: 
Chris@16: #else // defined(BOOST_NO_VOID_RETURNS)
Chris@16: 
Chris@16: private: // helpers, for static visitor interfaces (below)
Chris@16: 
Chris@16:     result_type execute_impl(argument_fwd_type operand, mpl::false_) const
Chris@16:     {
Chris@16:         return visitor_(operand);
Chris@16:     }
Chris@16: 
Chris@16:         BOOST_VARIANT_AUX_RETURN_VOID_TYPE
Chris@16:     execute_impl(argument_fwd_type operand, mpl::true_) const
Chris@16:     {
Chris@16:         visitor_(operand);
Chris@16:         BOOST_VARIANT_AUX_RETURN_VOID;
Chris@16:     }
Chris@16: 
Chris@16: public: // static visitor interfaces, cont.
Chris@16: 
Chris@16:         BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
Chris@16:     operator()(argument_fwd_type operand) const
Chris@16:     {
Chris@16:         typedef typename is_void<result_type>::type has_void_result;
Chris@16:         return execute_impl(operand, has_void_result());
Chris@16:     }
Chris@16: 
Chris@16: #endif // BOOST_NO_VOID_RETURNS workaround
Chris@16: 
Chris@16: };
Chris@16: 
Chris@16: template <typename R, typename T>
Chris@16: inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T))
Chris@16: {
Chris@16:     return visitor_ptr_t<T,R>(visitor);
Chris@16: }
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif// BOOST_VISITOR_VISITOR_PTR_HPP