sl@0: //-----------------------------------------------------------------------------
sl@0: // boost variant/get.hpp header file
sl@0: // See http://www.boost.org for updates, documentation, and revision history.
sl@0: //-----------------------------------------------------------------------------
sl@0: //
sl@0: // Copyright (c) 2003
sl@0: // Eric Friedman, Itay Maman
sl@0: //
sl@0: // Distributed under the Boost Software License, Version 1.0. (See
sl@0: // accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: 
sl@0: #ifndef BOOST_VARIANT_GET_HPP
sl@0: #define BOOST_VARIANT_GET_HPP
sl@0: 
sl@0: #include <exception>
sl@0: 
sl@0: #include "boost/config.hpp"
sl@0: #include "boost/detail/workaround.hpp"
sl@0: #include "boost/utility/addressof.hpp"
sl@0: #include "boost/variant/variant_fwd.hpp"
sl@0: 
sl@0: #include "boost/type_traits/add_reference.hpp"
sl@0: #include "boost/type_traits/add_pointer.hpp"
sl@0: 
sl@0: #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
sl@0: #   include "boost/mpl/bool.hpp"
sl@0: #   include "boost/mpl/or.hpp"
sl@0: #   include "boost/type_traits/is_same.hpp"
sl@0: #endif
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: //////////////////////////////////////////////////////////////////////////
sl@0: // class bad_get
sl@0: //
sl@0: // The exception thrown in the event of a failed get of a value.
sl@0: //
sl@0: class bad_get
sl@0:     : public std::exception
sl@0: {
sl@0: public: // std::exception implementation
sl@0: 
sl@0:     virtual const char * what() const throw()
sl@0:     {
sl@0:         return "boost::bad_get: "
sl@0:                "failed value get using boost::get";
sl@0:     }
sl@0: 
sl@0: };
sl@0: 
sl@0: //////////////////////////////////////////////////////////////////////////
sl@0: // function template get<T>
sl@0: //
sl@0: // Retrieves content of given variant object if content is of type T.
sl@0: // Otherwise: pointer ver. returns 0; reference ver. throws bad_get.
sl@0: //
sl@0: 
sl@0: namespace detail { namespace variant {
sl@0: 
sl@0: // (detail) class template get_visitor
sl@0: //
sl@0: // Generic static visitor that: if the value is of the specified type,
sl@0: // returns a pointer to the value it visits; else a null pointer.
sl@0: //
sl@0: template <typename T>
sl@0: struct get_visitor
sl@0: {
sl@0: private: // private typedefs
sl@0: 
sl@0:     typedef typename add_pointer<T>::type pointer;
sl@0:     typedef typename add_reference<T>::type reference;
sl@0: 
sl@0: public: // visitor typedefs
sl@0: 
sl@0:     typedef pointer result_type;
sl@0: 
sl@0: public: // visitor interfaces
sl@0: 
sl@0: #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
sl@0: 
sl@0:     pointer operator()(reference operand) const
sl@0:     {
sl@0:         return boost::addressof(operand);
sl@0:     }
sl@0: 
sl@0:     template <typename U>
sl@0:     pointer operator()(const U&) const
sl@0:     {
sl@0:         return static_cast<pointer>(0);
sl@0:     }
sl@0: 
sl@0: #else // MSVC6
sl@0: 
sl@0: private: // helpers, for visitor interfaces (below)
sl@0: 
sl@0:     pointer execute_impl(reference operand, mpl::true_) const
sl@0:     {
sl@0:         return boost::addressof(operand);
sl@0:     }
sl@0: 
sl@0:     template <typename U>
sl@0:     pointer execute_impl(const U& operand, mpl::false_) const
sl@0:     {
sl@0:         return static_cast<pointer>(0);
sl@0:     }
sl@0: 
sl@0: public: // visitor interfaces
sl@0: 
sl@0:     template <typename U>
sl@0:     pointer operator()(U& operand) const
sl@0:     {
sl@0:         // MSVC6 finds normal implementation (above) ambiguous,
sl@0:         // so we must explicitly disambiguate
sl@0: 
sl@0:         typedef typename mpl::or_<
sl@0:               is_same<U, T>
sl@0:             , is_same<const U, T>
sl@0:             >::type U_is_T;
sl@0: 
sl@0:         return execute_impl(operand, U_is_T());
sl@0:     }
sl@0: 
sl@0: #endif // MSVC6 workaround
sl@0: 
sl@0: };
sl@0: 
sl@0: }} // namespace detail::variant
sl@0: 
sl@0: #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
sl@0: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
sl@0:     BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)
sl@0: #else
sl@0: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
sl@0:     , t* = 0
sl@0: #endif
sl@0: 
sl@0: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
sl@0: inline
sl@0:     typename add_pointer<U>::type
sl@0: get(
sl@0:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
sl@0:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
sl@0:     )
sl@0: {
sl@0:     typedef typename add_pointer<U>::type U_ptr;
sl@0:     if (!operand) return static_cast<U_ptr>(0);
sl@0: 
sl@0:     detail::variant::get_visitor<U> v;
sl@0:     return operand->apply_visitor(v);
sl@0: }
sl@0: 
sl@0: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
sl@0: inline
sl@0:     typename add_pointer<const U>::type
sl@0: get(
sl@0:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
sl@0:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
sl@0:     )
sl@0: {
sl@0:     typedef typename add_pointer<const U>::type U_ptr;
sl@0:     if (!operand) return static_cast<U_ptr>(0);
sl@0: 
sl@0:     detail::variant::get_visitor<const U> v;
sl@0:     return operand->apply_visitor(v);
sl@0: }
sl@0: 
sl@0: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
sl@0: inline
sl@0:     typename add_reference<U>::type
sl@0: get(
sl@0:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
sl@0:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
sl@0:     )
sl@0: {
sl@0:     typedef typename add_pointer<U>::type U_ptr;
sl@0:     U_ptr result = get<U>(&operand);
sl@0: 
sl@0:     if (!result)
sl@0:         throw bad_get();
sl@0:     return *result;
sl@0: }
sl@0: 
sl@0: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
sl@0: inline
sl@0:     typename add_reference<const U>::type
sl@0: get(
sl@0:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
sl@0:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
sl@0:     )
sl@0: {
sl@0:     typedef typename add_pointer<const U>::type U_ptr;
sl@0:     U_ptr result = get<const U>(&operand);
sl@0: 
sl@0:     if (!result)
sl@0:         throw bad_get();
sl@0:     return *result;
sl@0: }
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_VARIANT_GET_HPP