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