williamr@2: //-----------------------------------------------------------------------------
williamr@2: // boost variant/get.hpp header file
williamr@2: // See http://www.boost.org for updates, documentation, and revision history.
williamr@2: //-----------------------------------------------------------------------------
williamr@2: //
williamr@2: // Copyright (c) 2003
williamr@2: // Eric Friedman, Itay Maman
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: 
williamr@2: #ifndef BOOST_VARIANT_GET_HPP
williamr@2: #define BOOST_VARIANT_GET_HPP
williamr@2: 
williamr@2: #include <exception>
williamr@2: 
williamr@2: #include "boost/config.hpp"
williamr@2: #include "boost/detail/workaround.hpp"
williamr@2: #include "boost/utility/addressof.hpp"
williamr@2: #include "boost/variant/variant_fwd.hpp"
williamr@2: 
williamr@2: #include "boost/type_traits/add_reference.hpp"
williamr@2: #include "boost/type_traits/add_pointer.hpp"
williamr@2: 
williamr@2: #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
williamr@2: #   include "boost/mpl/bool.hpp"
williamr@2: #   include "boost/mpl/or.hpp"
williamr@2: #   include "boost/type_traits/is_same.hpp"
williamr@2: #endif
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2: //////////////////////////////////////////////////////////////////////////
williamr@2: // class bad_get
williamr@2: //
williamr@2: // The exception thrown in the event of a failed get of a value.
williamr@2: //
williamr@2: class bad_get
williamr@2:     : public std::exception
williamr@2: {
williamr@2: public: // std::exception implementation
williamr@2: 
williamr@2:     virtual const char * what() const throw()
williamr@2:     {
williamr@2:         return "boost::bad_get: "
williamr@2:                "failed value get using boost::get";
williamr@2:     }
williamr@2: 
williamr@2: };
williamr@2: 
williamr@2: //////////////////////////////////////////////////////////////////////////
williamr@2: // function template get<T>
williamr@2: //
williamr@2: // Retrieves content of given variant object if content is of type T.
williamr@2: // Otherwise: pointer ver. returns 0; reference ver. throws bad_get.
williamr@2: //
williamr@2: 
williamr@2: namespace detail { namespace variant {
williamr@2: 
williamr@2: // (detail) class template get_visitor
williamr@2: //
williamr@2: // Generic static visitor that: if the value is of the specified type,
williamr@2: // returns a pointer to the value it visits; else a null pointer.
williamr@2: //
williamr@2: template <typename T>
williamr@2: struct get_visitor
williamr@2: {
williamr@2: private: // private typedefs
williamr@2: 
williamr@2:     typedef typename add_pointer<T>::type pointer;
williamr@2:     typedef typename add_reference<T>::type reference;
williamr@2: 
williamr@2: public: // visitor typedefs
williamr@2: 
williamr@2:     typedef pointer result_type;
williamr@2: 
williamr@2: public: // visitor interfaces
williamr@2: 
williamr@2: #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
williamr@2: 
williamr@2:     pointer operator()(reference operand) const
williamr@2:     {
williamr@2:         return boost::addressof(operand);
williamr@2:     }
williamr@2: 
williamr@2:     template <typename U>
williamr@2:     pointer operator()(const U&) const
williamr@2:     {
williamr@2:         return static_cast<pointer>(0);
williamr@2:     }
williamr@2: 
williamr@2: #else // MSVC6
williamr@2: 
williamr@2: private: // helpers, for visitor interfaces (below)
williamr@2: 
williamr@2:     pointer execute_impl(reference operand, mpl::true_) const
williamr@2:     {
williamr@2:         return boost::addressof(operand);
williamr@2:     }
williamr@2: 
williamr@2:     template <typename U>
williamr@2:     pointer execute_impl(const U& operand, mpl::false_) const
williamr@2:     {
williamr@2:         return static_cast<pointer>(0);
williamr@2:     }
williamr@2: 
williamr@2: public: // visitor interfaces
williamr@2: 
williamr@2:     template <typename U>
williamr@2:     pointer operator()(U& operand) const
williamr@2:     {
williamr@2:         // MSVC6 finds normal implementation (above) ambiguous,
williamr@2:         // so we must explicitly disambiguate
williamr@2: 
williamr@2:         typedef typename mpl::or_<
williamr@2:               is_same<U, T>
williamr@2:             , is_same<const U, T>
williamr@2:             >::type U_is_T;
williamr@2: 
williamr@2:         return execute_impl(operand, U_is_T());
williamr@2:     }
williamr@2: 
williamr@2: #endif // MSVC6 workaround
williamr@2: 
williamr@2: };
williamr@2: 
williamr@2: }} // namespace detail::variant
williamr@2: 
williamr@2: #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0551))
williamr@2: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
williamr@2:     BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)
williamr@2: #else
williamr@2: #   define BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(t)  \
williamr@2:     , t* = 0
williamr@2: #endif
williamr@2: 
williamr@2: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
williamr@2: inline
williamr@2:     typename add_pointer<U>::type
williamr@2: get(
williamr@2:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
williamr@2:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
williamr@2:     )
williamr@2: {
williamr@2:     typedef typename add_pointer<U>::type U_ptr;
williamr@2:     if (!operand) return static_cast<U_ptr>(0);
williamr@2: 
williamr@2:     detail::variant::get_visitor<U> v;
williamr@2:     return operand->apply_visitor(v);
williamr@2: }
williamr@2: 
williamr@2: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
williamr@2: inline
williamr@2:     typename add_pointer<const U>::type
williamr@2: get(
williamr@2:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >* operand
williamr@2:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
williamr@2:     )
williamr@2: {
williamr@2:     typedef typename add_pointer<const U>::type U_ptr;
williamr@2:     if (!operand) return static_cast<U_ptr>(0);
williamr@2: 
williamr@2:     detail::variant::get_visitor<const U> v;
williamr@2:     return operand->apply_visitor(v);
williamr@2: }
williamr@2: 
williamr@2: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
williamr@2: inline
williamr@2:     typename add_reference<U>::type
williamr@2: get(
williamr@2:       boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
williamr@2:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
williamr@2:     )
williamr@2: {
williamr@2:     typedef typename add_pointer<U>::type U_ptr;
williamr@2:     U_ptr result = get<U>(&operand);
williamr@2: 
williamr@2:     if (!result)
williamr@2:         throw bad_get();
williamr@2:     return *result;
williamr@2: }
williamr@2: 
williamr@2: template <typename U, BOOST_VARIANT_ENUM_PARAMS(typename T) >
williamr@2: inline
williamr@2:     typename add_reference<const U>::type
williamr@2: get(
williamr@2:       const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& operand
williamr@2:       BOOST_VARIANT_AUX_GET_EXPLICIT_TEMPLATE_TYPE(U)
williamr@2:     )
williamr@2: {
williamr@2:     typedef typename add_pointer<const U>::type U_ptr;
williamr@2:     U_ptr result = get<const U>(&operand);
williamr@2: 
williamr@2:     if (!result)
williamr@2:         throw bad_get();
williamr@2:     return *result;
williamr@2: }
williamr@2: 
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_VARIANT_GET_HPP