boost/variant/variant.hpp
//----------------------------------------------------------------------------- // boost variant/variant.hpp header file // See http://www.boost.org for updates, documentation, and revision history. //----------------------------------------------------------------------------- // // Copyright (c) 2002-2003 Eric Friedman, Itay Maman // Copyright (c) 2012-2024 Antony Polukhin // // 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) // Thanks to Adam Romanek for providing patches for exception-disabled env. #ifndef BOOST_VARIANT_VARIANT_HPP #define BOOST_VARIANT_VARIANT_HPP #include <cstddef> // for std::size_t #include <new> // for placement new #include <boost/type_index.hpp> #include <boost/variant/detail/config.hpp> #include <boost/mpl/aux_/value_wknd.hpp> #include <boost/variant/variant_fwd.hpp> #include <boost/variant/detail/backup_holder.hpp> #include <boost/variant/detail/enable_recursive_fwd.hpp> #include <boost/variant/detail/forced_return.hpp> #include <boost/variant/detail/initializer.hpp> #include <boost/variant/detail/make_variant_list.hpp> #include <boost/variant/detail/over_sequence.hpp> #include <boost/variant/detail/visitation_impl.hpp> #include <boost/variant/detail/hash_variant.hpp> #include <boost/variant/detail/std_hash.hpp> #include <boost/variant/detail/move.hpp> #include <boost/detail/reference_content.hpp> #include <boost/blank.hpp> #include <boost/integer/common_factor_ct.hpp> #include <boost/static_assert.hpp> #include <boost/type_traits/aligned_storage.hpp> #include <boost/type_traits/alignment_of.hpp> #include <boost/type_traits/add_const.hpp> #include <boost/type_traits/has_nothrow_constructor.hpp> #include <boost/type_traits/has_nothrow_copy.hpp> #include <boost/type_traits/is_nothrow_move_assignable.hpp> #include <boost/type_traits/is_nothrow_move_constructible.hpp> #include <boost/type_traits/is_const.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/type_traits/is_rvalue_reference.hpp> #include <boost/type_traits/is_constructible.hpp> #include <boost/type_traits/add_lvalue_reference.hpp> #include <boost/type_traits/declval.hpp> #include <boost/core/no_exceptions_support.hpp> #include <boost/core/enable_if.hpp> #include <boost/variant/recursive_wrapper_fwd.hpp> #include <boost/variant/static_visitor.hpp> #include <boost/mpl/assert.hpp> #include <boost/mpl/begin_end.hpp> #include <boost/mpl/bool.hpp> #include <boost/mpl/deref.hpp> #include <boost/mpl/empty.hpp> #include <boost/mpl/eval_if.hpp> #include <boost/mpl/find_if.hpp> #include <boost/mpl/fold.hpp> #include <boost/mpl/front.hpp> #include <boost/mpl/identity.hpp> #include <boost/mpl/if.hpp> #include <boost/mpl/insert_range.hpp> #include <boost/mpl/int.hpp> #include <boost/mpl/is_sequence.hpp> #include <boost/mpl/iterator_range.hpp> #include <boost/mpl/iter_fold_if.hpp> #include <boost/mpl/list.hpp> #include <boost/mpl/logical.hpp> #include <boost/mpl/max_element.hpp> #include <boost/mpl/next.hpp> #include <boost/mpl/not.hpp> #include <boost/mpl/pair.hpp> #include <boost/mpl/protect.hpp> #include <boost/mpl/push_front.hpp> #include <boost/mpl/same_as.hpp> #include <boost/mpl/size_t.hpp> #include <boost/mpl/sizeof.hpp> #include <boost/mpl/transform.hpp> /////////////////////////////////////////////////////////////////////////////// // Implementation Macros: // // BOOST_VARIANT_VISITATION_UNROLLING_LIMIT // Defined in boost/variant/detail/visitation_impl.hpp. // // BOOST_VARIANT_MINIMIZE_SIZE // When #defined, implementation employs all known means to minimize the // size of variant obje cts. However, often unsuccessful due to alignment // issues, and potentially harmful to runtime speed, so not enabled by // default. (TODO: Investigate further.) #if defined(BOOST_VARIANT_MINIMIZE_SIZE) # include <climits> // for SCHAR_MAX # include <boost/mpl/eval_if.hpp> # include <boost/mpl/equal_to.hpp> # include <boost/mpl/identity.hpp> # include <boost/mpl/int.hpp> # include <boost/mpl/if.hpp> # include <boost/mpl/less.hpp> # include <boost/mpl/long.hpp> # include <boost/mpl/O1_size.hpp> #endif namespace boost { namespace detail { namespace variant { /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction max_value // // Finds the maximum value of the unary metafunction F over Sequence. // template <typename Sequence, typename F> struct max_value { private: // helpers, for metafunction result (below) typedef typename mpl::transform1<Sequence, F>::type transformed_; typedef typename mpl::max_element<transformed_ >::type max_it; public: // metafunction result typedef typename mpl::deref<max_it>::type type; }; struct add_alignment { template <typename State, typename Item> struct apply : mpl::size_t< ::boost::integer::static_lcm< BOOST_MPL_AUX_VALUE_WKND(State)::value , ::boost::alignment_of<Item>::value >::value > {}; }; /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction find_fallback_type // // Provides a fallback (i.e., nothrow default-constructible) type from the // specified sequence, or no_fallback_type if not found. // // This implementation is designed to prefer boost::blank over other potential // fallback types, regardless of its position in the specified sequence. // class no_fallback_type; struct find_fallback_type_pred { template <typename Iterator> struct apply { private: typedef typename mpl::deref<Iterator>::type t_; public: typedef mpl::not_< has_nothrow_constructor<t_> > type; }; }; template <typename Types> struct find_fallback_type { private: // helpers, for metafunction result (below) typedef typename mpl::end<Types>::type end_it; // [Find the first suitable fallback type...] typedef typename mpl::iter_fold_if< Types , mpl::int_<0>, mpl::protect< mpl::next<> > , mpl::protect< find_fallback_type_pred > >::type first_result_; typedef typename first_result_::first first_result_index; typedef typename first_result_::second first_result_it; // [...now search the rest of the sequence for boost::blank...] typedef typename mpl::iter_fold_if< mpl::iterator_range< first_result_it,end_it > , first_result_index, mpl::protect< mpl::next<> > , mpl::protect< mpl::not_same_as<boost::blank> > >::type second_result_; typedef typename second_result_::second second_result_it; public: // metafunction result // [...and return the results of the search:] typedef typename mpl::eval_if< is_same< second_result_it,end_it > , mpl::if_< is_same< first_result_it,end_it > , mpl::pair< no_fallback_type,no_fallback_type > , first_result_ > , mpl::identity< second_result_ > >::type type; }; /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction is_variant_move_noexcept_constructible // // Returns true_type if all the types are nothrow move constructible. // template <class Types> struct is_variant_move_noexcept_constructible { typedef typename boost::mpl::find_if< Types, mpl::not_<boost::is_nothrow_move_constructible<boost::mpl::_1> > >::type iterator_t; typedef typename boost::mpl::end<Types>::type end_t; typedef typename boost::is_same< iterator_t, end_t >::type type; }; /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction is_variant_move_noexcept_assignable // // Returns true_type if all the types are nothrow move constructible. // template <class Types> struct is_variant_move_noexcept_assignable { typedef typename boost::mpl::find_if< Types, mpl::not_<boost::is_nothrow_move_assignable<boost::mpl::_1> > >::type iterator_t; typedef typename boost::mpl::end<Types>::type end_t; typedef typename boost::is_same< iterator_t, end_t >::type type; }; /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction is_variant_constructible_from // // Derives from true_type if at least one variant's type is constructible from T. // template <class T1, class T2> struct is_constructible_ext: boost::mpl::or_< boost::is_constructible< T1, T2 >, boost::is_constructible< T1, typename boost::add_lvalue_reference<T2>::type > > {}; template <class T, class Types> struct is_variant_constructible_from: boost::mpl::not_< boost::is_same< typename boost::mpl::find_if< Types, is_constructible_ext<boost::mpl::_1, T> >::type, typename boost::mpl::end<Types>::type > > {}; template <BOOST_VARIANT_ENUM_PARAMS(typename T), class Types> struct is_variant_constructible_from< boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Types >: boost::is_same< typename boost::mpl::find_if< typename boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>::recursive_enabled_types, mpl::not_< is_variant_constructible_from< boost::mpl::_1, Types> > >::type, typename boost::mpl::end< typename boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>::recursive_enabled_types >::type > {}; template <BOOST_VARIANT_ENUM_PARAMS(typename T), class Types> struct is_variant_constructible_from< const boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>& , Types >: is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Types > {}; template <BOOST_VARIANT_ENUM_PARAMS(typename T), class Types> struct is_variant_constructible_from< boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>& , Types >: is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Types > {}; template <BOOST_VARIANT_ENUM_PARAMS(typename T), class Types> struct is_variant_constructible_from< boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>&& , Types >: is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Types > {}; template <BOOST_VARIANT_ENUM_PARAMS(typename T), class Types> struct is_variant_constructible_from< boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)> const && , Types >: is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)>, Types > {}; /////////////////////////////////////////////////////////////////////////////// // (detail) metafunction make_storage // // Provides an aligned storage type capable of holding any of the types // specified in the given type-sequence. // template <typename Types, typename NeverUsesBackupFlag> struct make_storage { private: // helpers, for metafunction result (below) typedef typename mpl::eval_if< NeverUsesBackupFlag , mpl::identity< Types > , mpl::push_front< Types, backup_holder<void*> > >::type types; typedef typename max_value< types, mpl::sizeof_<mpl::_1> >::type max_size; #if !BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x0551)) typedef typename mpl::fold< types , mpl::size_t<1> , add_alignment >::type max_alignment; #else // borland // temporary workaround -- use maximal alignment typedef mpl::size_t< -1 > max_alignment; #endif // borland workaround public: // metafunction result typedef ::boost::aligned_storage< BOOST_MPL_AUX_VALUE_WKND(max_size)::value , BOOST_MPL_AUX_VALUE_WKND(max_alignment)::value > type; }; /////////////////////////////////////////////////////////////////////////////// // (detail) class destroyer // // Internal visitor that destroys the value it visits. // struct destroyer : public static_visitor<> { public: // visitor interfaces template <typename T> void internal_visit(T& operand, int) const BOOST_NOEXCEPT { operand.~T(); // must be noexcept #if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x0551)) || \ BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) (void)operand; // suppresses warnings #endif } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class template known_get // // Visitor that returns a reference to content of the specified type. // // Precondition: visited variant MUST contain logical content of type T. // template <typename T> class known_get : public static_visitor<T&> { public: // visitor interface T& operator()(T& operand) const BOOST_NOEXCEPT { return operand; } template <typename U> T& operator()(U&) const { // logical error to be here: see precondition above return ::boost::detail::variant::forced_return< T& >(); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class copy_into // // Internal visitor that copies the value it visits into the given buffer. // class copy_into : public static_visitor<> { private: // representation void* storage_; public: // structors explicit copy_into(void* storage) BOOST_NOEXCEPT : storage_(storage) { } public: // internal visitor interface template <typename T> void internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const { new(storage_) T( operand.get() ); } template <typename T> void internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) const { new(storage_) T( operand.get() ); } template <typename T> void internal_visit(const T& operand, int) const { new(storage_) T(operand); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class move_into // // Internal visitor that moves the value it visits into the given buffer. // class move_into : public static_visitor<> { private: // representation void* storage_; public: // structors explicit move_into(void* storage) BOOST_NOEXCEPT : storage_(storage) { } public: // internal visitor interface template <typename T> void internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const { new(storage_) T( ::boost::detail::variant::move(operand.get()) ); } template <typename T> void internal_visit(T& operand, int) const BOOST_NOEXCEPT_IF(BOOST_NOEXCEPT_EXPR(T(boost::declval<T>()))) { new(storage_) T(::boost::detail::variant::move(operand)); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class assign_storage // // Internal visitor that assigns the given storage (which must be a // constructed value of the same type) to the value it visits. // struct assign_storage : public static_visitor<> { private: // representation const void* rhs_storage_; public: // structors explicit assign_storage(const void* rhs_storage) BOOST_NOEXCEPT : rhs_storage_(rhs_storage) { } public: // internal visitor interfaces template <typename T> void internal_visit(backup_holder<T>& lhs_content, long) const { lhs_content.get() = static_cast< const backup_holder<T>* >(rhs_storage_)->get(); } template <typename T> void internal_visit(const backup_holder<T>& lhs_content, long) const { lhs_content.get() = static_cast< const backup_holder<T>* >(rhs_storage_)->get(); } template <typename T> void internal_visit(T& lhs_content, int) const { // NOTE TO USER : // Compile error here indicates one of variant's bounded types does // not meet the requirements of the Assignable concept. Thus, // variant is not Assignable. // // Hint: Are any of the bounded types const-qualified or references? // lhs_content = *static_cast< const T* >(rhs_storage_); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class move_storage // // Internal visitor that moves the given storage (which must be a // constructed value of the same type) to the value it visits. // struct move_storage : public static_visitor<> { private: // representation void* rhs_storage_; public: // structors explicit move_storage(void* rhs_storage) BOOST_NOEXCEPT : rhs_storage_(rhs_storage) { } public: // internal visitor interfaces template <typename T> void internal_visit(backup_holder<T>& lhs_content, long) const { lhs_content.get() = ::boost::detail::variant::move(static_cast<backup_holder<T>* >(rhs_storage_)->get()); } template <typename T> void internal_visit(const backup_holder<T>& lhs_content, long) const { lhs_content.get() = ::boost::detail::variant::move(static_cast<backup_holder<T>* >(rhs_storage_)->get()); } template <typename T> void internal_visit(T& lhs_content, int) const { // NOTE TO USER : // Compile error here indicates one of variant's bounded types does // not meet the requirements of the Assignable concept. Thus, // variant is not Assignable. // // Hint: Are any of the bounded types const-qualified or references? // lhs_content = ::boost::detail::variant::move(*static_cast<T* >(rhs_storage_)); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class direct_assigner // // Generic static visitor that: if and only if the visited value is of the // specified type, assigns the given value to the visited value and returns // true; else returns false. // template <typename T> class direct_assigner : public static_visitor<bool> { private: // representation const T& rhs_; public: // structors explicit direct_assigner(const T& rhs) BOOST_NOEXCEPT : rhs_(rhs) { } public: // visitor interface bool operator()(T& lhs) { lhs = rhs_; return true; } template <typename U> bool operator()(U&) BOOST_NOEXCEPT { return false; } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated direct_assigner& operator= (direct_assigner const&); #endif }; /////////////////////////////////////////////////////////////////////////////// // (detail) class direct_mover // // Generic static visitor that: if and only if the visited value is of the // specified type, move assigns the given value to the visited value and returns // true; else returns false. // template <typename T> class direct_mover : public static_visitor<bool> { private: // representation T& rhs_; public: // structors explicit direct_mover(T& rhs) BOOST_NOEXCEPT : rhs_(rhs) { } public: // visitor interface bool operator()(T& lhs) { lhs = ::boost::detail::variant::move(rhs_); return true; } template <typename U> bool operator()(U&) BOOST_NOEXCEPT { return false; } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated direct_mover& operator= (direct_mover const&); #endif }; /////////////////////////////////////////////////////////////////////////////// // (detail) class backup_assigner // // Internal visitor that "assigns" the given value to the visited value, // using backup to recover if the destroy-copy sequence fails. // // NOTE: This needs to be a friend of variant, as it needs access to // indicate_which, indicate_backup_which, etc. // template <typename Variant> class backup_assigner : public static_visitor<> { private: // representation Variant& lhs_; int rhs_which_; const void* rhs_content_; void (*copy_rhs_content_)(void*, const void*); public: // structors template<class RhsT> backup_assigner(Variant& lhs, int rhs_which, const RhsT& rhs_content) : lhs_(lhs) , rhs_which_(rhs_which) , rhs_content_(&rhs_content) , copy_rhs_content_(&construct_impl<RhsT>) { } private: // helpers, for visitor interface (below) template<class RhsT> static void construct_impl(void* addr, const void* obj) { new(addr) RhsT(*static_cast<const RhsT*>(obj)); } template <typename LhsT> void backup_assign_impl( backup_holder<LhsT>& lhs_content , mpl::false_ // is_nothrow_move_constructible , long ) { // Move lhs content to backup... backup_holder<LhsT> backup_lhs_content(0); backup_lhs_content.swap(lhs_content); // nothrow // ...destroy lhs content... lhs_content.~backup_holder<LhsT>(); // nothrow BOOST_TRY { // ...and attempt to copy rhs content into lhs storage: copy_rhs_content_(lhs_.storage_.address(), rhs_content_); } BOOST_CATCH (...) { // In case of failure, copy backup pointer to lhs storage... new(lhs_.storage_.address()) backup_holder<LhsT>( 0 ); // nothrow static_cast<backup_holder<LhsT>* >(lhs_.storage_.address()) ->swap(backup_lhs_content); // nothrow // ...and rethrow: BOOST_RETHROW; } BOOST_CATCH_END // In case of success, indicate new content type: lhs_.indicate_which(rhs_which_); // nothrow } template <typename LhsT> void backup_assign_impl( LhsT& lhs_content , mpl::true_ // is_nothrow_move_constructible , int ) { // Move lhs content to backup... LhsT backup_lhs_content( ::boost::detail::variant::move(lhs_content) ); // nothrow // ...destroy lhs content... lhs_content.~LhsT(); // nothrow BOOST_TRY { // ...and attempt to copy rhs content into lhs storage: copy_rhs_content_(lhs_.storage_.address(), rhs_content_); } BOOST_CATCH (...) { // In case of failure, restore backup content to lhs storage... new(lhs_.storage_.address()) LhsT( ::boost::detail::variant::move(backup_lhs_content) ); // nothrow // ...and rethrow: BOOST_RETHROW; } BOOST_CATCH_END // In case of success, indicate new content type: lhs_.indicate_which(rhs_which_); // nothrow } template <typename LhsT> void backup_assign_impl( LhsT& lhs_content , mpl::false_ // is_nothrow_move_constructible , int ) { // Backup lhs content... LhsT* backup_lhs_ptr = new LhsT(lhs_content); // ...destroy lhs content... lhs_content.~LhsT(); // nothrow BOOST_TRY { // ...and attempt to copy rhs content into lhs storage: copy_rhs_content_(lhs_.storage_.address(), rhs_content_); } BOOST_CATCH (...) { // In case of failure, copy backup pointer to lhs storage... new(lhs_.storage_.address()) backup_holder<LhsT>( backup_lhs_ptr ); // nothrow // ...indicate now using backup... lhs_.indicate_backup_which( lhs_.which() ); // nothrow // ...and rethrow: BOOST_RETHROW; } BOOST_CATCH_END // In case of success, indicate new content type... lhs_.indicate_which(rhs_which_); // nothrow // ...and delete backup: delete backup_lhs_ptr; // nothrow } public: // visitor interface template <typename LhsT> void internal_visit(LhsT& lhs_content, int) { typedef typename is_nothrow_move_constructible<LhsT>::type nothrow_move; backup_assign_impl( lhs_content, nothrow_move(), 1L); } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated backup_assigner& operator= (backup_assigner const&); #endif }; /////////////////////////////////////////////////////////////////////////////// // (detail) class swap_with // // Visitor that swaps visited value with content of given variant. // // Precondition: Given variant MUST have same logical type as visited value. // template <typename Variant> struct swap_with : public static_visitor<> { private: // representation Variant& toswap_; public: // structors explicit swap_with(Variant& toswap) BOOST_NOEXCEPT : toswap_(toswap) { } public: // internal visitor interfaces template <typename T> void operator()(T& operand) const { // Since the precondition ensures types are same, get T... known_get<T> getter; T& other = toswap_.apply_visitor(getter); // ...and swap: ::boost::detail::variant::move_swap( operand, other ); } private: swap_with& operator=(const swap_with&); }; /////////////////////////////////////////////////////////////////////////////// // (detail) class reflect // // Generic static visitor that performs a typeid on the value it visits. // class reflect : public static_visitor<const boost::typeindex::type_info&> { public: // visitor interfaces template <typename T> const boost::typeindex::type_info& operator()(const T&) const BOOST_NOEXCEPT { return boost::typeindex::type_id<T>().type_info(); } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class comparer // // Generic static visitor that compares the content of the given lhs variant // with the visited rhs content using Comp. // // Precondition: lhs.which() == rhs.which() // template <typename Variant, typename Comp> class comparer : public static_visitor<bool> { private: // representation const Variant& lhs_; public: // structors explicit comparer(const Variant& lhs) BOOST_NOEXCEPT : lhs_(lhs) { } public: // visitor interfaces template <typename T> bool operator()(T& rhs_content) const { // Since the precondition ensures lhs and rhs types are same, get T... known_get<T> getter; const T& lhs_content = lhs_.apply_visitor(getter); // ...and compare lhs and rhs contents: return Comp()(lhs_content, rhs_content); } private: comparer& operator=(const comparer&); }; /////////////////////////////////////////////////////////////////////////////// // (detail) class equal_comp // // Generic function object compares lhs with rhs using operator==. // struct equal_comp { template <typename T> bool operator()(const T& lhs, const T& rhs) const { return lhs == rhs; } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class less_comp // // Generic function object compares lhs with rhs using operator<. // struct less_comp { template <typename T> bool operator()(const T& lhs, const T& rhs) const { return lhs < rhs; } }; /////////////////////////////////////////////////////////////////////////////// // (detail) class template invoke_visitor // // Internal visitor that invokes the given visitor using: // * for wrappers (e.g., recursive_wrapper), the wrapper's held value. // * for all other values, the value itself. // template <typename Visitor, bool MoveSemantics> class invoke_visitor { private: // representation Visitor& visitor_; public: // visitor typedefs typedef typename Visitor::result_type result_type; public: // structors explicit invoke_visitor(Visitor& visitor) BOOST_NOEXCEPT : visitor_(visitor) { } public: // internal visitor interfaces //using workaround with is_same<T, T> to prenvent compilation error, because we need to use T in enable_if to make SFINAE work template <typename T> typename enable_if_c<MoveSemantics && is_same<T, T>::value, result_type>::type internal_visit(T&& operand, int) { return visitor_(std::move(operand)); } //using workaround with is_same<T, T> to prenvent compilation error, because we need to use T in enable_if to make SFINAE work template <typename T> typename disable_if_c<MoveSemantics && is_same<T, T>::value, result_type>::type internal_visit(T&& operand, int) { return visitor_(operand); } public: // internal visitor interfaces, cont. template <typename T> result_type internal_visit(boost::recursive_wrapper<T>& operand, long) { return internal_visit( operand.get(), 1L ); } template <typename T> result_type internal_visit(const boost::recursive_wrapper<T>& operand, long) { return internal_visit( operand.get(), 1L ); } template <typename T> result_type internal_visit(boost::detail::reference_content<T>& operand, long) { return internal_visit( operand.get(), 1L ); } template <typename T> result_type internal_visit(const boost::detail::reference_content<T>& operand, long) { return internal_visit( operand.get(), 1L ); } template <typename T> result_type internal_visit(boost::detail::variant::backup_holder<T>& operand, long) { return internal_visit( operand.get(), 1L ); } template <typename T> result_type internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) { return internal_visit( operand.get(), 1L ); } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated invoke_visitor& operator= (invoke_visitor const&); #endif }; }} // namespace detail::variant /////////////////////////////////////////////////////////////////////////////// // class template variant (concept inspired by Andrei Alexandrescu) // // See docs and boost/variant/variant_fwd.hpp for more information. // template < typename T0_ , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(typename T) > class variant { private: // helpers, for typedefs (below) typedef variant wknd_self_t; struct is_recursive_ : detail::variant::is_recursive_flag<T0_> { }; typedef typename mpl::eval_if< is_recursive_ , T0_ , mpl::identity< T0_ > >::type unwrapped_T0_; struct is_sequence_based_ : detail::variant::is_over_sequence<unwrapped_T0_> { }; private: // helpers, for typedefs (below) typedef typename mpl::eval_if< is_sequence_based_ , unwrapped_T0_ // over_sequence<...>::type , detail::variant::make_variant_list< unwrapped_T0_ , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) > >::type specified_types; BOOST_STATIC_ASSERT(( ::boost::mpl::not_< mpl::empty<specified_types> >::value )); public: // public typedefs typedef typename mpl::eval_if< is_recursive_ , mpl::transform< specified_types , mpl::protect< detail::variant::quoted_enable_recursive<wknd_self_t> > > , mpl::identity< specified_types > >::type recursive_enabled_types; // used by is_variant_constructible_from<> trait typedef typename mpl::transform< recursive_enabled_types , unwrap_recursive<mpl::_1> >::type types; private: // internal typedefs typedef typename mpl::transform< recursive_enabled_types , mpl::protect< detail::make_reference_content<> > >::type internal_types; typedef typename mpl::front< internal_types >::type internal_T0; private: // helpers, for representation (below) typedef typename detail::variant::find_fallback_type< internal_types >::type fallback_type_result_; typedef typename fallback_type_result_::first fallback_type_index_; typedef typename fallback_type_result_::second fallback_type_; struct has_fallback_type_ : mpl::not_< is_same< fallback_type_, detail::variant::no_fallback_type > > { }; typedef has_fallback_type_ never_uses_backup_flag; typedef typename detail::variant::make_storage< internal_types, never_uses_backup_flag >::type storage_t; typedef typename detail::variant::is_variant_move_noexcept_constructible< internal_types > variant_move_noexcept_constructible; typedef typename detail::variant::is_variant_move_noexcept_assignable< internal_types > variant_move_noexcept_assignable; private: // helpers, for representation (below) // which_ on: // * [0, size<internal_types>) indicates stack content // * [-size<internal_types>, 0) indicates pointer to heap backup // if which_ >= 0: // * then which() -> which_ // * else which() -> -(which_ + 1) #if !defined(BOOST_VARIANT_MINIMIZE_SIZE) typedef int which_t; #else // defined(BOOST_VARIANT_MINIMIZE_SIZE) // [if O1_size available, then attempt which_t size optimization...] // [select signed char if fewer than SCHAR_MAX types, else signed int:] typedef typename mpl::eval_if< mpl::equal_to< mpl::O1_size<internal_types>, mpl::long_<-1> > , mpl::identity< int > , mpl::if_< mpl::less< mpl::O1_size<internal_types>, mpl::int_<SCHAR_MAX> > , signed char , int > >::type which_t; #endif // BOOST_VARIANT_MINIMIZE_SIZE switch // representation -- private when possible #if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) private: #else public: #endif which_t which_; storage_t storage_; void indicate_which(int which_arg) BOOST_NOEXCEPT { which_ = static_cast<which_t>( which_arg ); } void indicate_backup_which(int which_arg) BOOST_NOEXCEPT { which_ = static_cast<which_t>( -(which_arg + 1) ); } private: // helpers, for queries (below) bool using_backup() const BOOST_NOEXCEPT { return which_ < 0; } public: // queries int which() const BOOST_NOEXCEPT { // If using heap backup... if (using_backup()) // ...then return adjusted which_: return -(which_ + 1); // Otherwise, return which_ directly: return which_; } private: // helpers, for structors (below) struct initializer : BOOST_VARIANT_AUX_INITIALIZER_T( recursive_enabled_types, recursive_enabled_T ) { }; void destroy_content() BOOST_NOEXCEPT { detail::variant::destroyer visitor; this->internal_apply_visitor(visitor); } public: // structors ~variant() BOOST_NOEXCEPT { destroy_content(); } variant() #if !(defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x5130)) BOOST_NOEXCEPT_IF(boost::has_nothrow_constructor<internal_T0>::value) #endif { #ifdef _MSC_VER #pragma warning( push ) // behavior change: an object of POD type constructed with an initializer of the form () will be default-initialized #pragma warning( disable : 4345 ) #endif // NOTE TO USER : // Compile error from here indicates that the first bound // type is not default-constructible, and so variant cannot // support its own default-construction. // new( storage_.address() ) internal_T0(); indicate_which(0); // zero is the index of the first bounded type #ifdef _MSC_VER #pragma warning( pop ) #endif } private: // helpers, for structors, cont. (below) class convert_copy_into : public static_visitor<int> { private: // representation void* storage_; public: // structors explicit convert_copy_into(void* storage) BOOST_NOEXCEPT : storage_(storage) { } public: // internal visitor interfaces (below) template <typename T> int internal_visit(T& operand, int) const { // NOTE TO USER : // Compile error here indicates one of the source variant's types // cannot be unambiguously converted to the destination variant's // types (or that no conversion exists). // return initializer::initialize(storage_, operand); } # if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x0564)) template <typename T> result_type internal_visit(const T& operand, int) const { return initializer::initialize(storage_, operand); } # endif template <typename T> int internal_visit(boost::detail::reference_content<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::detail::reference_content<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(boost::recursive_wrapper<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::recursive_wrapper<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } }; friend class convert_copy_into; class convert_move_into : public static_visitor<int> { private: // representation void* storage_; public: // structors explicit convert_move_into(void* storage) BOOST_NOEXCEPT : storage_(storage) { } public: // internal visitor interfaces (below) template <typename T> int internal_visit(T& operand, int) const { // NOTE TO USER : // Compile error here indicates one of the source variant's types // cannot be unambiguously converted to the destination variant's // types (or that no conversion exists). // return initializer::initialize(storage_, detail::variant::move(operand) ); } template <typename T> int internal_visit(boost::detail::reference_content<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::detail::reference_content<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(boost::detail::variant::backup_holder<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::detail::variant::backup_holder<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(boost::recursive_wrapper<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } template <typename T> int internal_visit(const boost::recursive_wrapper<T>& operand, long) const { return internal_visit( operand.get(), 1L ); } }; friend class convert_move_into; private: // helpers, for structors, below template <typename T> void convert_construct( T& operand , int , mpl::false_ = mpl::false_() // is_foreign_variant ) { // NOTE TO USER : // Compile error here indicates that the given type is not // unambiguously convertible to one of the variant's types // (or that no conversion exists). // indicate_which( initializer::initialize( storage_.address() , operand ) ); } template <typename T> typename boost::enable_if<boost::is_rvalue_reference<T&&> >::type convert_construct( T&& operand , int , mpl::false_ = mpl::false_() // is_foreign_variant ) { // NOTE TO USER : // Compile error here indicates that the given type is not // unambiguously convertible to one of the variant's types // (or that no conversion exists). // indicate_which( initializer::initialize( storage_.address() , detail::variant::move(operand) ) ); } template <typename Variant> void convert_construct( Variant& operand , long , mpl::true_// is_foreign_variant ) { convert_copy_into visitor(storage_.address()); indicate_which( operand.internal_apply_visitor(visitor) ); } template <typename Variant> typename boost::enable_if<boost::is_rvalue_reference<Variant&&> >::type convert_construct( Variant&& operand , long , mpl::true_// is_foreign_variant ) { convert_move_into visitor(storage_.address()); indicate_which( operand.internal_apply_visitor(visitor) ); } template <typename Variant> void convert_construct_variant(Variant& operand) { // [Determine if the given variant is itself a bounded type, or if its // content needs to be converted (i.e., it is a 'foreign' variant):] // typedef typename mpl::find_if< types , is_same< add_const<mpl::_1> , const Variant > >::type found_it; typedef typename mpl::end<types>::type not_found; typedef typename is_same< found_it, not_found >::type is_foreign_variant; // Convert construct from operand: convert_construct( operand, 1L , is_foreign_variant() ); } template <typename Variant> typename boost::enable_if<boost::is_rvalue_reference<Variant&&> >::type convert_construct_variant(Variant&& operand) { // [Determine if the given variant is itself a bounded type, or if its // content needs to be converted (i.e., it is a 'foreign' variant):] // typedef typename mpl::find_if< types , is_same< add_const<mpl::_1> , const Variant > >::type found_it; typedef typename mpl::end<types>::type not_found; typedef typename is_same< found_it, not_found >::type is_foreign_variant; // Convert move construct from operand: convert_construct( detail::variant::move(operand), 1L , is_foreign_variant() ); } template <BOOST_VARIANT_ENUM_PARAMS(typename U)> typename boost::enable_if<mpl::or_< boost::is_same<boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>, variant>, boost::detail::variant::is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>&, internal_types> > >::type convert_construct( boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>& operand , long ) { convert_construct_variant(operand); } template <BOOST_VARIANT_ENUM_PARAMS(typename U)> typename boost::enable_if<mpl::or_< boost::is_same<boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>, variant>, boost::detail::variant::is_variant_constructible_from<const boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>&, internal_types> > >::type convert_construct( const boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>& operand , long ) { convert_construct_variant(operand); } template <BOOST_VARIANT_ENUM_PARAMS(typename U)> typename boost::enable_if<mpl::or_< boost::is_same<boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>, variant>, boost::detail::variant::is_variant_constructible_from<boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>&&, internal_types> > >::type convert_construct( boost::variant<BOOST_VARIANT_ENUM_PARAMS(U)>&& operand , long ) { convert_construct_variant( detail::variant::move(operand) ); } public: // structors, cont. template <typename T> variant(const T& operand, typename boost::enable_if<mpl::or_< mpl::and_< mpl::not_< boost::is_same<T, variant> >, boost::detail::variant::is_variant_constructible_from<const T&, internal_types> >, boost::is_same<T, boost::recursive_variant_> >, bool >::type = true) { convert_construct(operand, 1L); } template <typename T> variant( T& operand , typename boost::enable_if<mpl::or_< mpl::and_< mpl::not_< is_const<T> >, mpl::not_< boost::is_same<T, variant> >, boost::detail::variant::is_variant_constructible_from<T&, internal_types> >, boost::is_same<T, boost::recursive_variant_> >, bool >::type = true ) { convert_construct(operand, 1L); } template <class T> variant(T&& operand, typename boost::enable_if<mpl::or_< mpl::and_< boost::is_rvalue_reference<T&&>, mpl::not_< boost::is_const<T> >, mpl::not_< boost::is_same<T, variant> >, boost::detail::variant::is_variant_constructible_from<T&&, internal_types> >, boost::is_same<T, boost::recursive_variant_> >, bool >::type = true) { convert_construct( detail::variant::move(operand), 1L); } public: // structors, cont. // [MSVC6 requires copy constructor appear after template constructors] variant(const variant& operand) { // Copy the value of operand into *this... detail::variant::copy_into visitor( storage_.address() ); operand.internal_apply_visitor(visitor); // ...and activate the *this's primary storage on success: indicate_which(operand.which()); } variant(variant&& operand) BOOST_NOEXCEPT_IF(variant_move_noexcept_constructible::type::value) { // Move the value of operand into *this... detail::variant::move_into visitor( storage_.address() ); operand.internal_apply_visitor(visitor); // ...and activate the *this's primary storage on success: indicate_which(operand.which()); } private: // helpers, for modifiers (below) template <typename Variant> friend class detail::variant::backup_assigner; // class assigner // // Internal visitor that "assigns" the visited value to the given variant // by appropriate destruction and copy-construction. // class assigner : public static_visitor<> { protected: // representation variant& lhs_; const int rhs_which_; public: // structors assigner(variant& lhs, int rhs_which) BOOST_NOEXCEPT : lhs_(lhs) , rhs_which_(rhs_which) { } protected: // helpers, for internal visitor interface (below) template <typename RhsT, typename B1, typename B2> void assign_impl( const RhsT& rhs_content , mpl::true_ // has_nothrow_copy , B1 // is_nothrow_move_constructible , B2 // has_fallback_type ) const BOOST_NOEXCEPT { // Destroy lhs's content... lhs_.destroy_content(); // nothrow // ...copy rhs content into lhs's storage... new(lhs_.storage_.address()) RhsT( rhs_content ); // nothrow // ...and indicate new content type: lhs_.indicate_which(rhs_which_); // nothrow } template <typename RhsT, typename B> void assign_impl( const RhsT& rhs_content , mpl::false_ // has_nothrow_copy , mpl::true_ // is_nothrow_move_constructible , B // has_fallback_type ) const { // Attempt to make a temporary copy (so as to move it below)... RhsT temp(rhs_content); // ...and upon success destroy lhs's content... lhs_.destroy_content(); // nothrow // ...move the temporary copy into lhs's storage... new(lhs_.storage_.address()) RhsT( detail::variant::move(temp) ); // nothrow // ...and indicate new content type: lhs_.indicate_which(rhs_which_); // nothrow } void construct_fallback() const BOOST_NOEXCEPT { // In case of failure, default-construct fallback type in lhs's storage... new (lhs_.storage_.address()) fallback_type_; // nothrow // ...indicate construction of fallback type... lhs_.indicate_which( BOOST_MPL_AUX_VALUE_WKND(fallback_type_index_)::value ); // nothrow } template <typename RhsT> void assign_impl( const RhsT& rhs_content , mpl::false_ // has_nothrow_copy , mpl::false_ // is_nothrow_move_constructible , mpl::true_ // has_fallback_type ) const { // Destroy lhs's content... lhs_.destroy_content(); // nothrow BOOST_TRY { // ...and attempt to copy rhs's content into lhs's storage: new(lhs_.storage_.address()) RhsT( rhs_content ); } BOOST_CATCH (...) { construct_fallback(); // ...and rethrow: BOOST_RETHROW; } BOOST_CATCH_END // In the event of success, indicate new content type: lhs_.indicate_which(rhs_which_); // nothrow } template <typename RhsT> void assign_impl( const RhsT& rhs_content , mpl::false_ // has_nothrow_copy , mpl::false_ // is_nothrow_move_constructible , mpl::false_ // has_fallback_type ) const { detail::variant::backup_assigner<wknd_self_t> visitor(lhs_, rhs_which_, rhs_content); lhs_.internal_apply_visitor(visitor); } public: // internal visitor interfaces template <typename RhsT> void internal_visit(const RhsT& rhs_content, int) const { typedef typename has_nothrow_copy<RhsT>::type nothrow_copy; typedef typename mpl::or_< // reduces compile-time nothrow_copy , is_nothrow_move_constructible<RhsT> >::type nothrow_move_constructor; assign_impl( rhs_content , nothrow_copy() , nothrow_move_constructor() , has_fallback_type_() ); } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated assigner& operator= (assigner const&); #endif }; friend class assigner; // class move_assigner // // Internal visitor that "move assigns" the visited value to the given variant // by appropriate destruction and move-construction. // class move_assigner : public assigner { public: // structors move_assigner(variant& lhs, int rhs_which) BOOST_NOEXCEPT : assigner(lhs, rhs_which) { } private: // helpers, for internal visitor interface (below) template <typename RhsT, typename B2> void assign_impl( RhsT& rhs_content , mpl::true_ // has_nothrow_copy , mpl::false_ // is_nothrow_move_constructible , B2 // has_fallback_type ) const BOOST_NOEXCEPT { assigner::assign_impl(rhs_content, mpl::true_(), mpl::false_(), B2()); } template <typename RhsT, typename B, typename B2> void assign_impl( RhsT& rhs_content , B // has_nothrow_copy , mpl::true_ // is_nothrow_move_constructible , B2 // has_fallback_type ) const BOOST_NOEXCEPT { // ...destroy lhs's content... assigner::lhs_.destroy_content(); // nothrow // ...move the rhs_content into lhs's storage... new(assigner::lhs_.storage_.address()) RhsT( detail::variant::move(rhs_content) ); // nothrow // ...and indicate new content type: assigner::lhs_.indicate_which(assigner::rhs_which_); // nothrow } template <typename RhsT> void assign_impl( RhsT& rhs_content , mpl::false_ // has_nothrow_copy , mpl::false_ // is_nothrow_move_constructible , mpl::true_ // has_fallback_type ) const { // Destroy lhs's content... assigner::lhs_.destroy_content(); // nothrow BOOST_TRY { // ...and attempt to copy rhs's content into lhs's storage: new(assigner::lhs_.storage_.address()) RhsT( detail::variant::move(rhs_content) ); } BOOST_CATCH (...) { assigner::construct_fallback(); // ...and rethrow: BOOST_RETHROW; } BOOST_CATCH_END // In the event of success, indicate new content type: assigner::lhs_.indicate_which(assigner::rhs_which_); // nothrow } template <typename RhsT> void assign_impl( RhsT& rhs_content , mpl::false_ // has_nothrow_copy , mpl::false_ // is_nothrow_move_constructible , mpl::false_ // has_fallback_type ) const { assigner::assign_impl(rhs_content, mpl::false_(), mpl::false_(), mpl::false_()); } public: // internal visitor interfaces template <typename RhsT> void internal_visit(RhsT& rhs_content, int) const { typedef typename is_nothrow_move_constructible<RhsT>::type nothrow_move_constructor; typedef typename mpl::or_< // reduces compile-time nothrow_move_constructor , has_nothrow_copy<RhsT> >::type nothrow_copy; assign_impl( rhs_content , nothrow_copy() , nothrow_move_constructor() , has_fallback_type_() ); } #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1600)) private: // silence MSVC warning C4512: assignment operator could not be generated move_assigner& operator= (move_assigner const&); #endif }; friend class move_assigner; void variant_assign(const variant& rhs) { // If the contained types are EXACTLY the same... if (which_ == rhs.which_) { // ...then assign rhs's storage to lhs's content: detail::variant::assign_storage visitor(rhs.storage_.address()); this->internal_apply_visitor(visitor); } else { // Otherwise, perform general (copy-based) variant assignment: assigner visitor(*this, rhs.which()); rhs.internal_apply_visitor(visitor); } } void variant_assign(variant&& rhs) { // If the contained types are EXACTLY the same... if (which_ == rhs.which_) { // ...then move rhs's storage to lhs's content: detail::variant::move_storage visitor(rhs.storage_.address()); this->internal_apply_visitor(visitor); } else { // Otherwise, perform general (move-based) variant assignment: move_assigner visitor(*this, rhs.which()); rhs.internal_apply_visitor(visitor); } } private: // helpers, for modifiers (below) template <typename T> void assign(const T& rhs) { // If direct T-to-T assignment is not possible... detail::variant::direct_assigner<T> direct_assign(rhs); if (this->apply_visitor(direct_assign) == false) { // ...then convert rhs to variant and assign: // // While potentially inefficient, the following construction of a // variant allows T as any type convertible to one of the bounded // types without excessive code redundancy. // variant temp(rhs); variant_assign( detail::variant::move(temp) ); } } template <typename T> void move_assign(T&& rhs) { // If direct T-to-T move assignment is not possible... detail::variant::direct_mover<T> direct_move(rhs); if (this->apply_visitor(direct_move) == false) { // ...then convert rhs to variant and assign: // // While potentially inefficient, the following construction of a // variant allows T as any type convertible to one of the bounded // types without excessive code redundancy. // variant temp( detail::variant::move(rhs) ); variant_assign( detail::variant::move(temp) ); } } public: // modifiers #if !BOOST_WORKAROUND(BOOST_CLANG_VERSION, BOOST_TESTED_AT(150000)) || BOOST_CXX_VERSION <= 202002L template <class T> typename boost::enable_if< boost::mpl::and_< boost::is_rvalue_reference<T&&>, mpl::not_< boost::is_const<T> >, boost::detail::variant::is_variant_constructible_from<T&&, internal_types> >, variant& >::type operator=(T&& rhs) { move_assign( detail::variant::move(rhs) ); return *this; } #endif template <typename T> typename boost::enable_if< mpl::or_< boost::is_same<T, variant>, boost::detail::variant::is_variant_constructible_from<const T&, internal_types> >, variant& >::type operator=(const T& rhs) { assign(rhs); return *this; } // [MSVC6 requires copy assign appear after templated operator=] variant& operator=(const variant& rhs) { variant_assign(rhs); return *this; } variant& operator=(variant&& rhs) #if !defined(__GNUC__) || (__GNUC__ != 4) || (__GNUC_MINOR__ > 6) || defined(__clang__) BOOST_NOEXCEPT_IF(variant_move_noexcept_constructible::type::value && variant_move_noexcept_assignable::type::value) #endif { variant_assign( detail::variant::move(rhs) ); return *this; } void swap(variant& rhs) { // If the contained types are the same... if (which() == rhs.which()) { // ...then swap the values directly: detail::variant::swap_with<variant> visitor(rhs); this->apply_visitor(visitor); } else { // ...otherwise, perform general variant swap: variant tmp( detail::variant::move(rhs) ); rhs = detail::variant::move(*this); *this = detail::variant::move(tmp); } } public: // queries // // NOTE: member which() defined above. // bool empty() const BOOST_NOEXCEPT { return false; } const boost::typeindex::type_info& type() const { detail::variant::reflect visitor; return this->apply_visitor(visitor); } public: // prevent comparison with foreign types template <typename U> void operator==(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } template <typename U> void operator<(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } template <typename U> void operator!=(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } template <typename U> void operator>(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } template <typename U> void operator<=(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } template <typename U> void operator>=(const U&) const { BOOST_STATIC_ASSERT( false && sizeof(U) ); } public: // comparison operators // [MSVC6 requires these operators appear after template operators] bool operator==(const variant& rhs) const { if (this->which() != rhs.which()) return false; detail::variant::comparer< variant, detail::variant::equal_comp > visitor(*this); return rhs.apply_visitor(visitor); } bool operator<(const variant& rhs) const { // // Dirk Schreib suggested this collating order. // if (this->which() != rhs.which()) return this->which() < rhs.which(); detail::variant::comparer< variant, detail::variant::less_comp > visitor(*this); return rhs.apply_visitor(visitor); } /////////////////////////////////////////////////////////////////////////////// // comparison operators != > <= >= inline bool operator!=(const variant& rhs) const { return !(*this == rhs); } inline bool operator>(const variant& rhs) const { return rhs < *this; } inline bool operator<=(const variant& rhs) const { return !(*this > rhs); } inline bool operator>=(const variant& rhs) const { return !(*this < rhs); } // helpers, for visitation support (below) -- private when possible #if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) template < BOOST_VARIANT_ENUM_PARAMS(typename U) > friend class variant; private: #else// defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) public: #endif// !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) template <typename Visitor, typename VoidPtrCV> BOOST_FORCEINLINE static typename Visitor::result_type internal_apply_visitor_impl( int internal_which , int logical_which , Visitor& visitor , VoidPtrCV storage ) { typedef mpl::int_<0> first_which; typedef typename mpl::begin<internal_types>::type first_it; typedef typename mpl::end<internal_types>::type last_it; typedef detail::variant::visitation_impl_step< first_it, last_it > first_step; return detail::variant::visitation_impl( internal_which, logical_which , visitor, storage, mpl::false_() , never_uses_backup_flag() , static_cast<first_which*>(0), static_cast<first_step*>(0) ); } template <typename Visitor> BOOST_FORCEINLINE typename Visitor::result_type internal_apply_visitor(Visitor& visitor) { return internal_apply_visitor_impl( which_, which(), visitor, storage_.address() ); } template <typename Visitor> BOOST_FORCEINLINE typename Visitor::result_type internal_apply_visitor(Visitor& visitor) const { return internal_apply_visitor_impl( which_, which(), visitor, storage_.address() ); } public: // visitation support template <typename Visitor> typename Visitor::result_type apply_visitor(Visitor& visitor) && { detail::variant::invoke_visitor<Visitor, true> invoker(visitor); return this->internal_apply_visitor(invoker); } template <typename Visitor> typename Visitor::result_type apply_visitor(Visitor& visitor) const&& { detail::variant::invoke_visitor<Visitor, true> invoker(visitor); return this->internal_apply_visitor(invoker); } template <typename Visitor> typename Visitor::result_type apply_visitor(Visitor& visitor) & { detail::variant::invoke_visitor<Visitor, false> invoker(visitor); return this->internal_apply_visitor(invoker); } template <typename Visitor> typename Visitor::result_type apply_visitor(Visitor& visitor) const & { detail::variant::invoke_visitor<Visitor, false> invoker(visitor); return this->internal_apply_visitor(invoker); } }; // class variant /////////////////////////////////////////////////////////////////////////////// // metafunction make_variant_over // // See docs and boost/variant/variant_fwd.hpp for more information. // template <typename Types> struct make_variant_over { private: // precondition assertions BOOST_STATIC_ASSERT(( ::boost::mpl::is_sequence<Types>::value )); typedef typename boost::mpl::insert_range< boost::mpl::list<> , boost::mpl::end< boost::mpl::list<> >::type , Types >::type copied_sequence_t; public: // metafunction result typedef variant< detail::variant::over_sequence<copied_sequence_t> > type; }; /////////////////////////////////////////////////////////////////////////////// // function template swap // // Swaps two variants of the same type (i.e., identical specification). // template < BOOST_VARIANT_ENUM_PARAMS(typename T) > inline void swap( variant< BOOST_VARIANT_ENUM_PARAMS(T) >& lhs , variant< BOOST_VARIANT_ENUM_PARAMS(T) >& rhs ) { lhs.swap(rhs); } } // namespace boost // implementation additions #if !defined(BOOST_NO_IOSTREAM) #include <boost/variant/detail/variant_io.hpp> #endif // BOOST_NO_IOSTREAM #endif // BOOST_VARIANT_VARIANT_HPP