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variant
// <variant> -*- C++ -*- // Copyright (C) 2016-2021 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file variant * This is the `<variant>` C++ Library header. */ #ifndef _GLIBCXX_VARIANT #define _GLIBCXX_VARIANT 1 #pragma GCC system_header #if __cplusplus >= 201703L #include <type_traits> #include <utility> #include <bits/enable_special_members.h> #include <bits/functexcept.h> #include <bits/move.h> #include <bits/functional_hash.h> #include <bits/invoke.h> #include <ext/aligned_buffer.h> #include <bits/parse_numbers.h> #include <bits/stl_iterator_base_types.h> #include <bits/stl_iterator_base_funcs.h> #include <bits/stl_construct.h> #if __cplusplus > 201703L # include <compare> #endif namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace __detail { namespace __variant { template<size_t _Np, typename... _Types> struct _Nth_type; template<size_t _Np, typename _First, typename... _Rest> struct _Nth_type<_Np, _First, _Rest...> : _Nth_type<_Np-1, _Rest...> { }; template<typename _First, typename... _Rest> struct _Nth_type<0, _First, _Rest...> { using type = _First; }; } // namespace __variant } // namespace __detail #define __cpp_lib_variant 202102L template<typename... _Types> class tuple; template<typename... _Types> class variant; template <typename> struct hash; template<typename _Variant> struct variant_size; template<typename _Variant> struct variant_size<const _Variant> : variant_size<_Variant> {}; template<typename _Variant> struct variant_size<volatile _Variant> : variant_size<_Variant> {}; template<typename _Variant> struct variant_size<const volatile _Variant> : variant_size<_Variant> {}; template<typename... _Types> struct variant_size<variant<_Types...>> : std::integral_constant<size_t, sizeof...(_Types)> {}; template<typename _Variant> inline constexpr size_t variant_size_v = variant_size<_Variant>::value; template<size_t _Np, typename _Variant> struct variant_alternative; template<size_t _Np, typename _First, typename... _Rest> struct variant_alternative<_Np, variant<_First, _Rest...>> : variant_alternative<_Np-1, variant<_Rest...>> {}; template<typename _First, typename... _Rest> struct variant_alternative<0, variant<_First, _Rest...>> { using type = _First; }; template<size_t _Np, typename _Variant> using variant_alternative_t = typename variant_alternative<_Np, _Variant>::type; template<size_t _Np, typename _Variant> struct variant_alternative<_Np, const _Variant> { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; }; template<size_t _Np, typename _Variant> struct variant_alternative<_Np, volatile _Variant> { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; }; template<size_t _Np, typename _Variant> struct variant_alternative<_Np, const volatile _Variant> { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; }; inline constexpr size_t variant_npos = -1; template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>>& get(variant<_Types...>&); template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>>&& get(variant<_Types...>&&); template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>> const& get(const variant<_Types...>&); template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>> const&& get(const variant<_Types...>&&); template<typename _Result_type, typename _Visitor, typename... _Variants> constexpr decltype(auto) __do_visit(_Visitor&& __visitor, _Variants&&... __variants); template <typename... _Types, typename _Tp> decltype(auto) __variant_cast(_Tp&& __rhs) { if constexpr (is_lvalue_reference_v<_Tp>) { if constexpr (is_const_v<remove_reference_t<_Tp>>) return static_cast<const variant<_Types...>&>(__rhs); else return static_cast<variant<_Types...>&>(__rhs); } else return static_cast<variant<_Types...>&&>(__rhs); } namespace __detail { namespace __variant { // Returns the first appearance of _Tp in _Types. // Returns sizeof...(_Types) if _Tp is not in _Types. template<typename _Tp, typename... _Types> struct __index_of : std::integral_constant<size_t, 0> {}; template<typename _Tp, typename... _Types> inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value; template<typename _Tp, typename _First, typename... _Rest> struct __index_of<_Tp, _First, _Rest...> : std::integral_constant<size_t, is_same_v<_Tp, _First> ? 0 : __index_of_v<_Tp, _Rest...> + 1> {}; // used for raw visitation struct __variant_cookie {}; // used for raw visitation with indices passed in struct __variant_idx_cookie { using type = __variant_idx_cookie; }; // Used to enable deduction (and same-type checking) for std::visit: template<typename _Tp> struct __deduce_visit_result { using type = _Tp; }; // Visit variants that might be valueless. template<typename _Visitor, typename... _Variants> constexpr void __raw_visit(_Visitor&& __visitor, _Variants&&... __variants) { std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor), std::forward<_Variants>(__variants)...); } // Visit variants that might be valueless, passing indices to the visitor. template<typename _Visitor, typename... _Variants> constexpr void __raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants) { std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor), std::forward<_Variants>(__variants)...); } // The __as function templates implement the exposition-only "as-variant" template<typename... _Types> constexpr std::variant<_Types...>& __as(std::variant<_Types...>& __v) noexcept { return __v; } template<typename... _Types> constexpr const std::variant<_Types...>& __as(const std::variant<_Types...>& __v) noexcept { return __v; } template<typename... _Types> constexpr std::variant<_Types...>&& __as(std::variant<_Types...>&& __v) noexcept { return std::move(__v); } template<typename... _Types> constexpr const std::variant<_Types...>&& __as(const std::variant<_Types...>&& __v) noexcept { return std::move(__v); } // _Uninitialized<T> is guaranteed to be a trivially destructible type, // even if T is not. template<typename _Type, bool = std::is_trivially_destructible_v<_Type>> struct _Uninitialized; template<typename _Type> struct _Uninitialized<_Type, true> { template<typename... _Args> constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args) : _M_storage(std::forward<_Args>(__args)...) { } constexpr const _Type& _M_get() const & noexcept { return _M_storage; } constexpr _Type& _M_get() & noexcept { return _M_storage; } constexpr const _Type&& _M_get() const && noexcept { return std::move(_M_storage); } constexpr _Type&& _M_get() && noexcept { return std::move(_M_storage); } _Type _M_storage; }; template<typename _Type> struct _Uninitialized<_Type, false> { template<typename... _Args> constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args) { ::new ((void*)std::addressof(_M_storage)) _Type(std::forward<_Args>(__args)...); } const _Type& _M_get() const & noexcept { return *_M_storage._M_ptr(); } _Type& _M_get() & noexcept { return *_M_storage._M_ptr(); } const _Type&& _M_get() const && noexcept { return std::move(*_M_storage._M_ptr()); } _Type&& _M_get() && noexcept { return std::move(*_M_storage._M_ptr()); } __gnu_cxx::__aligned_membuf<_Type> _M_storage; }; template<typename _Union> constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u) noexcept { return std::forward<_Union>(__u)._M_first._M_get(); } template<size_t _Np, typename _Union> constexpr decltype(auto) __get(in_place_index_t<_Np>, _Union&& __u) noexcept { return __variant::__get(in_place_index<_Np-1>, std::forward<_Union>(__u)._M_rest); } // Returns the typed storage for __v. template<size_t _Np, typename _Variant> constexpr decltype(auto) __get(_Variant&& __v) noexcept { return __variant::__get(std::in_place_index<_Np>, std::forward<_Variant>(__v)._M_u); } template<typename... _Types> struct _Traits { static constexpr bool _S_default_ctor = is_default_constructible_v<typename _Nth_type<0, _Types...>::type>; static constexpr bool _S_copy_ctor = (is_copy_constructible_v<_Types> && ...); static constexpr bool _S_move_ctor = (is_move_constructible_v<_Types> && ...); static constexpr bool _S_copy_assign = _S_copy_ctor && (is_copy_assignable_v<_Types> && ...); static constexpr bool _S_move_assign = _S_move_ctor && (is_move_assignable_v<_Types> && ...); static constexpr bool _S_trivial_dtor = (is_trivially_destructible_v<_Types> && ...); static constexpr bool _S_trivial_copy_ctor = (is_trivially_copy_constructible_v<_Types> && ...); static constexpr bool _S_trivial_move_ctor = (is_trivially_move_constructible_v<_Types> && ...); static constexpr bool _S_trivial_copy_assign = _S_trivial_dtor && _S_trivial_copy_ctor && (is_trivially_copy_assignable_v<_Types> && ...); static constexpr bool _S_trivial_move_assign = _S_trivial_dtor && _S_trivial_move_ctor && (is_trivially_move_assignable_v<_Types> && ...); // The following nothrow traits are for non-trivial SMFs. Trivial SMFs // are always nothrow. static constexpr bool _S_nothrow_default_ctor = is_nothrow_default_constructible_v< typename _Nth_type<0, _Types...>::type>; static constexpr bool _S_nothrow_copy_ctor = false; static constexpr bool _S_nothrow_move_ctor = (is_nothrow_move_constructible_v<_Types> && ...); static constexpr bool _S_nothrow_copy_assign = false; static constexpr bool _S_nothrow_move_assign = _S_nothrow_move_ctor && (is_nothrow_move_assignable_v<_Types> && ...); }; // Defines members and ctors. template<typename... _Types> union _Variadic_union { }; template<typename _First, typename... _Rest> union _Variadic_union<_First, _Rest...> { constexpr _Variadic_union() : _M_rest() { } template<typename... _Args> constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args) : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) { } template<size_t _Np, typename... _Args> constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) { } _Uninitialized<_First> _M_first; _Variadic_union<_Rest...> _M_rest; }; // _Never_valueless_alt is true for variant alternatives that can // always be placed in a variant without it becoming valueless. // For suitably-small, trivially copyable types we can create temporaries // on the stack and then memcpy them into place. template<typename _Tp> struct _Never_valueless_alt : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>> { }; // Specialize _Never_valueless_alt for other types which have a // non-throwing and cheap move construction and move assignment operator, // so that emplacing the type will provide the strong exception-safety // guarantee, by creating and moving a temporary. // Whether _Never_valueless_alt<T> is true or not affects the ABI of a // variant using that alternative, so we can't change the value later! // True if every alternative in _Types... can be emplaced in a variant // without it becoming valueless. If this is true, variant<_Types...> // can never be valueless, which enables some minor optimizations. template <typename... _Types> constexpr bool __never_valueless() { return _Traits<_Types...>::_S_move_assign && (_Never_valueless_alt<_Types>::value && ...); } // Defines index and the dtor, possibly trivial. template<bool __trivially_destructible, typename... _Types> struct _Variant_storage; template <typename... _Types> using __select_index = typename __select_int::_Select_int_base<sizeof...(_Types), unsigned char, unsigned short>::type::value_type; template<typename... _Types> struct _Variant_storage<false, _Types...> { constexpr _Variant_storage() : _M_index(static_cast<__index_type>(variant_npos)) { } template<size_t _Np, typename... _Args> constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), _M_index{_Np} { } void _M_reset() { if (!_M_valid()) [[unlikely]] return; std::__do_visit<void>([](auto&& __this_mem) mutable { std::_Destroy(std::__addressof(__this_mem)); }, __variant_cast<_Types...>(*this)); _M_index = static_cast<__index_type>(variant_npos); } ~_Variant_storage() { _M_reset(); } constexpr bool _M_valid() const noexcept { if constexpr (__variant::__never_valueless<_Types...>()) return true; return this->_M_index != __index_type(variant_npos); } _Variadic_union<_Types...> _M_u; using __index_type = __select_index<_Types...>; __index_type _M_index; }; template<typename... _Types> struct _Variant_storage<true, _Types...> { constexpr _Variant_storage() : _M_index(static_cast<__index_type>(variant_npos)) { } template<size_t _Np, typename... _Args> constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), _M_index{_Np} { } void _M_reset() noexcept { _M_index = static_cast<__index_type>(variant_npos); } constexpr bool _M_valid() const noexcept { if constexpr (__variant::__never_valueless<_Types...>()) return true; return this->_M_index != static_cast<__index_type>(variant_npos); } _Variadic_union<_Types...> _M_u; using __index_type = __select_index<_Types...>; __index_type _M_index; }; template<typename... _Types> using _Variant_storage_alias = _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; template<typename _Tp, typename _Up> void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem) { void* __storage = std::addressof(__lhs._M_u); using _Type = remove_reference_t<decltype(__rhs_mem)>; if constexpr (!is_same_v<_Type, __variant_cookie>) ::new (__storage) _Type(std::forward<decltype(__rhs_mem)>(__rhs_mem)); } template<typename... _Types, typename _Tp, typename _Up> void __variant_construct(_Tp&& __lhs, _Up&& __rhs) { __lhs._M_index = __rhs._M_index; __variant::__raw_visit([&__lhs](auto&& __rhs_mem) mutable { __variant_construct_single(std::forward<_Tp>(__lhs), std::forward<decltype(__rhs_mem)>(__rhs_mem)); }, __variant_cast<_Types...>(std::forward<_Up>(__rhs))); } // The following are (Copy|Move) (ctor|assign) layers for forwarding // triviality and handling non-trivial SMF behaviors. template<bool, typename... _Types> struct _Copy_ctor_base : _Variant_storage_alias<_Types...> { using _Base = _Variant_storage_alias<_Types...>; using _Base::_Base; _Copy_ctor_base(const _Copy_ctor_base& __rhs) noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor) { __variant_construct<_Types...>(*this, __rhs); } _Copy_ctor_base(_Copy_ctor_base&&) = default; _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default; _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default; }; template<typename... _Types> struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...> { using _Base = _Variant_storage_alias<_Types...>; using _Base::_Base; }; template<typename... _Types> using _Copy_ctor_alias = _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; template<bool, typename... _Types> struct _Move_ctor_base : _Copy_ctor_alias<_Types...> { using _Base = _Copy_ctor_alias<_Types...>; using _Base::_Base; _Move_ctor_base(_Move_ctor_base&& __rhs) noexcept(_Traits<_Types...>::_S_nothrow_move_ctor) { __variant_construct<_Types...>(*this, std::move(__rhs)); } template<typename _Up> void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs) { this->_M_reset(); __variant_construct_single(*this, std::forward<_Up>(__rhs)); this->_M_index = __rhs_index; } template<typename _Up> void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs) { this->_M_reset(); __variant_construct_single(*this, __rhs); this->_M_index = __rhs_index; } _Move_ctor_base(const _Move_ctor_base&) = default; _Move_ctor_base& operator=(const _Move_ctor_base&) = default; _Move_ctor_base& operator=(_Move_ctor_base&&) = default; }; template<typename... _Types> struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...> { using _Base = _Copy_ctor_alias<_Types...>; using _Base::_Base; template<typename _Up> void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs) { this->_M_reset(); __variant_construct_single(*this, std::forward<_Up>(__rhs)); this->_M_index = __rhs_index; } template<typename _Up> void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs) { this->_M_reset(); __variant_construct_single(*this, __rhs); this->_M_index = __rhs_index; } }; template<typename... _Types> using _Move_ctor_alias = _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; template<bool, typename... _Types> struct _Copy_assign_base : _Move_ctor_alias<_Types...> { using _Base = _Move_ctor_alias<_Types...>; using _Base::_Base; _Copy_assign_base& operator=(const _Copy_assign_base& __rhs) noexcept(_Traits<_Types...>::_S_nothrow_copy_assign) { __variant::__raw_idx_visit( [this](auto&& __rhs_mem, auto __rhs_index) mutable { if constexpr (__rhs_index != variant_npos) { if (this->_M_index == __rhs_index) __variant::__get<__rhs_index>(*this) = __rhs_mem; else { using __rhs_type = __remove_cvref_t<decltype(__rhs_mem)>; if constexpr (is_nothrow_copy_constructible_v<__rhs_type> || !is_nothrow_move_constructible_v<__rhs_type>) // The standard says this->emplace<__rhs_type>(__rhs_mem) // should be used here, but _M_destructive_copy is // equivalent in this case. Either copy construction // doesn't throw, so _M_destructive_copy gives strong // exception safety guarantee, or both copy construction // and move construction can throw, so emplace only gives // basic exception safety anyway. this->_M_destructive_copy(__rhs_index, __rhs_mem); else __variant_cast<_Types...>(*this) = variant<_Types...>(std::in_place_index<__rhs_index>, __rhs_mem); } } else this->_M_reset(); }, __variant_cast<_Types...>(__rhs)); return *this; } _Copy_assign_base(const _Copy_assign_base&) = default; _Copy_assign_base(_Copy_assign_base&&) = default; _Copy_assign_base& operator=(_Copy_assign_base&&) = default; }; template<typename... _Types> struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...> { using _Base = _Move_ctor_alias<_Types...>; using _Base::_Base; }; template<typename... _Types> using _Copy_assign_alias = _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>; template<bool, typename... _Types> struct _Move_assign_base : _Copy_assign_alias<_Types...> { using _Base = _Copy_assign_alias<_Types...>; using _Base::_Base; _Move_assign_base& operator=(_Move_assign_base&& __rhs) noexcept(_Traits<_Types...>::_S_nothrow_move_assign) { __variant::__raw_idx_visit( [this](auto&& __rhs_mem, auto __rhs_index) mutable { if constexpr (__rhs_index != variant_npos) { if (this->_M_index == __rhs_index) __variant::__get<__rhs_index>(*this) = std::move(__rhs_mem); else __variant_cast<_Types...>(*this) .template emplace<__rhs_index>(std::move(__rhs_mem)); } else this->_M_reset(); }, __variant_cast<_Types...>(__rhs)); return *this; } _Move_assign_base(const _Move_assign_base&) = default; _Move_assign_base(_Move_assign_base&&) = default; _Move_assign_base& operator=(const _Move_assign_base&) = default; }; template<typename... _Types> struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...> { using _Base = _Copy_assign_alias<_Types...>; using _Base::_Base; }; template<typename... _Types> using _Move_assign_alias = _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>; template<typename... _Types> struct _Variant_base : _Move_assign_alias<_Types...> { using _Base = _Move_assign_alias<_Types...>; constexpr _Variant_base() noexcept(_Traits<_Types...>::_S_nothrow_default_ctor) : _Variant_base(in_place_index<0>) { } template<size_t _Np, typename... _Args> constexpr explicit _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args) : _Base(__i, std::forward<_Args>(__args)...) { } _Variant_base(const _Variant_base&) = default; _Variant_base(_Variant_base&&) = default; _Variant_base& operator=(const _Variant_base&) = default; _Variant_base& operator=(_Variant_base&&) = default; }; // For how many times does _Tp appear in _Tuple? template<typename _Tp, typename _Tuple> struct __tuple_count; template<typename _Tp, typename _Tuple> inline constexpr size_t __tuple_count_v = __tuple_count<_Tp, _Tuple>::value; template<typename _Tp, typename... _Types> struct __tuple_count<_Tp, tuple<_Types...>> : integral_constant<size_t, 0> { }; template<typename _Tp, typename _First, typename... _Rest> struct __tuple_count<_Tp, tuple<_First, _Rest...>> : integral_constant< size_t, __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { }; // TODO: Reuse this in <tuple> ? template<typename _Tp, typename... _Types> inline constexpr bool __exactly_once = __tuple_count_v<_Tp, tuple<_Types...>> == 1; // Helper used to check for valid conversions that don't involve narrowing. template<typename _Ti> struct _Arr { _Ti _M_x[1]; }; // "Build an imaginary function FUN(Ti) for each alternative type Ti" template<size_t _Ind, typename _Tp, typename _Ti, typename = void> struct _Build_FUN { // This function means 'using _Build_FUN<I, T, Ti>::_S_fun;' is valid, // but only static functions will be considered in the call below. void _S_fun(); }; // "... for which Ti x[] = {std::forward<T>(t)}; is well-formed." template<size_t _Ind, typename _Tp, typename _Ti> struct _Build_FUN<_Ind, _Tp, _Ti, void_t<decltype(_Arr<_Ti>{{std::declval<_Tp>()}})>> { // This is the FUN function for type _Ti, with index _Ind static integral_constant<size_t, _Ind> _S_fun(_Ti); }; template<typename _Tp, typename _Variant, typename = make_index_sequence<variant_size_v<_Variant>>> struct _Build_FUNs; template<typename _Tp, typename... _Ti, size_t... _Ind> struct _Build_FUNs<_Tp, variant<_Ti...>, index_sequence<_Ind...>> : _Build_FUN<_Ind, _Tp, _Ti>... { using _Build_FUN<_Ind, _Tp, _Ti>::_S_fun...; }; // The index j of the overload FUN(Tj) selected by overload resolution // for FUN(std::forward<_Tp>(t)) template<typename _Tp, typename _Variant> using _FUN_type = decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>())); // The index selected for FUN(std::forward<T>(t)), or variant_npos if none. template<typename _Tp, typename _Variant, typename = void> struct __accepted_index : integral_constant<size_t, variant_npos> { }; template<typename _Tp, typename _Variant> struct __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>> : _FUN_type<_Tp, _Variant> { }; template <typename _Maybe_variant_cookie, typename _Variant> struct _Extra_visit_slot_needed { template <typename> struct _Variant_never_valueless; template <typename... _Types> struct _Variant_never_valueless<variant<_Types...>> : bool_constant<__variant::__never_valueless<_Types...>()> {}; static constexpr bool value = (is_same_v<_Maybe_variant_cookie, __variant_cookie> || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>) && !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value; }; // Used for storing a multi-dimensional vtable. template<typename _Tp, size_t... _Dimensions> struct _Multi_array; // Partial specialization with rank zero, stores a single _Tp element. template<typename _Tp> struct _Multi_array<_Tp> { template<typename> struct __untag_result : false_type { using element_type = _Tp; }; template <typename... _Args> struct __untag_result<const void(*)(_Args...)> : false_type { using element_type = void(*)(_Args...); }; template <typename... _Args> struct __untag_result<__variant_cookie(*)(_Args...)> : false_type { using element_type = void(*)(_Args...); }; template <typename... _Args> struct __untag_result<__variant_idx_cookie(*)(_Args...)> : false_type { using element_type = void(*)(_Args...); }; template <typename _Res, typename... _Args> struct __untag_result<__deduce_visit_result<_Res>(*)(_Args...)> : true_type { using element_type = _Res(*)(_Args...); }; using __result_is_deduced = __untag_result<_Tp>; constexpr const typename __untag_result<_Tp>::element_type& _M_access() const { return _M_data; } typename __untag_result<_Tp>::element_type _M_data; }; // Partial specialization with rank >= 1. template<typename _Ret, typename _Visitor, typename... _Variants, size_t __first, size_t... __rest> struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...> { static constexpr size_t __index = sizeof...(_Variants) - sizeof...(__rest) - 1; using _Variant = typename _Nth_type<__index, _Variants...>::type; static constexpr int __do_cookie = _Extra_visit_slot_needed<_Ret, _Variant>::value ? 1 : 0; using _Tp = _Ret(*)(_Visitor, _Variants...); template<typename... _Args> constexpr decltype(auto) _M_access(size_t __first_index, _Args... __rest_indices) const { return _M_arr[__first_index + __do_cookie] ._M_access(__rest_indices...); } _Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie]; }; // Creates a multi-dimensional vtable recursively. // // For example, // visit([](auto, auto){}, // variant<int, char>(), // typedef'ed as V1 // variant<float, double, long double>()) // typedef'ed as V2 // will trigger instantiations of: // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>, // tuple<V1&&, V2&&>, std::index_sequence<>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, // tuple<V1&&, V2&&>, std::index_sequence<0>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<0, 0>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<0, 1>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<0, 2>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, // tuple<V1&&, V2&&>, std::index_sequence<1>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<1, 0>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<1, 1>> // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, // tuple<V1&&, V2&&>, std::index_sequence<1, 2>> // The returned multi-dimensional vtable can be fast accessed by the visitor // using index calculation. template<typename _Array_type, typename _Index_seq> struct __gen_vtable_impl; // Defines the _S_apply() member that returns a _Multi_array populated // with function pointers that perform the visitation expressions e(m) // for each valid pack of indexes into the variant types _Variants. // // This partial specialization builds up the index sequences by recursively // calling _S_apply() on the next specialization of __gen_vtable_impl. // The base case of the recursion defines the actual function pointers. template<typename _Result_type, typename _Visitor, size_t... __dimensions, typename... _Variants, size_t... __indices> struct __gen_vtable_impl< _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, std::index_sequence<__indices...>> { using _Next = remove_reference_t<typename _Nth_type<sizeof...(__indices), _Variants...>::type>; using _Array_type = _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>; static constexpr _Array_type _S_apply() { _Array_type __vtable{}; _S_apply_all_alts( __vtable, make_index_sequence<variant_size_v<_Next>>()); return __vtable; } template<size_t... __var_indices> static constexpr void _S_apply_all_alts(_Array_type& __vtable, std::index_sequence<__var_indices...>) { if constexpr (_Extra_visit_slot_needed<_Result_type, _Next>::value) (_S_apply_single_alt<true, __var_indices>( __vtable._M_arr[__var_indices + 1], &(__vtable._M_arr[0])), ...); else (_S_apply_single_alt<false, __var_indices>( __vtable._M_arr[__var_indices]), ...); } template<bool __do_cookie, size_t __index, typename _Tp> static constexpr void _S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr) { if constexpr (__do_cookie) { __element = __gen_vtable_impl< _Tp, std::index_sequence<__indices..., __index>>::_S_apply(); *__cookie_element = __gen_vtable_impl< _Tp, std::index_sequence<__indices..., variant_npos>>::_S_apply(); } else { auto __tmp_element = __gen_vtable_impl< remove_reference_t<decltype(__element)>, std::index_sequence<__indices..., __index>>::_S_apply(); static_assert(is_same_v<_Tp, decltype(__tmp_element)>, "std::visit requires the visitor to have the same " "return type for all alternatives of a variant"); __element = __tmp_element; } } }; // This partial specialization is the base case for the recursion. // It populates a _Multi_array element with the address of a function // that invokes the visitor with the alternatives specified by __indices. template<typename _Result_type, typename _Visitor, typename... _Variants, size_t... __indices> struct __gen_vtable_impl< _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, std::index_sequence<__indices...>> { using _Array_type = _Multi_array<_Result_type (*)(_Visitor, _Variants...)>; template<size_t __index, typename _Variant> static constexpr decltype(auto) __element_by_index_or_cookie(_Variant&& __var) noexcept { if constexpr (__index != variant_npos) return __variant::__get<__index>(std::forward<_Variant>(__var)); else return __variant_cookie{}; } static constexpr decltype(auto) __visit_invoke(_Visitor&& __visitor, _Variants... __vars) { if constexpr (is_same_v<_Result_type, __variant_idx_cookie>) // For raw visitation using indices, pass the indices to the visitor // and discard the return value: std::__invoke(std::forward<_Visitor>(__visitor), __element_by_index_or_cookie<__indices>( std::forward<_Variants>(__vars))..., integral_constant<size_t, __indices>()...); else if constexpr (is_same_v<_Result_type, __variant_cookie>) // For raw visitation without indices, and discard the return value: std::__invoke(std::forward<_Visitor>(__visitor), __element_by_index_or_cookie<__indices>( std::forward<_Variants>(__vars))...); else if constexpr (_Array_type::__result_is_deduced::value) // For the usual std::visit case deduce the return value: return std::__invoke(std::forward<_Visitor>(__visitor), __element_by_index_or_cookie<__indices>( std::forward<_Variants>(__vars))...); else // for std::visit<R> use INVOKE<R> return std::__invoke_r<_Result_type>( std::forward<_Visitor>(__visitor), __variant::__get<__indices>(std::forward<_Variants>(__vars))...); } static constexpr auto _S_apply() { if constexpr (_Array_type::__result_is_deduced::value) { constexpr bool __visit_ret_type_mismatch = !is_same_v<typename _Result_type::type, decltype(__visit_invoke(std::declval<_Visitor>(), std::declval<_Variants>()...))>; if constexpr (__visit_ret_type_mismatch) { struct __cannot_match {}; return __cannot_match{}; } else return _Array_type{&__visit_invoke}; } else return _Array_type{&__visit_invoke}; } }; template<typename _Result_type, typename _Visitor, typename... _Variants> struct __gen_vtable { using _Array_type = _Multi_array<_Result_type (*)(_Visitor, _Variants...), variant_size_v<remove_reference_t<_Variants>>...>; static constexpr _Array_type _S_vtable = __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply(); }; template<size_t _Np, typename _Tp> struct _Base_dedup : public _Tp { }; template<typename _Variant, typename __indices> struct _Variant_hash_base; template<typename... _Types, size_t... __indices> struct _Variant_hash_base<variant<_Types...>, std::index_sequence<__indices...>> : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { }; // Equivalent to decltype(get<_Np>(as-variant(declval<_Variant>()))) template<size_t _Np, typename _Variant, typename _AsV = decltype(__variant::__as(std::declval<_Variant>())), typename _Tp = variant_alternative_t<_Np, remove_reference_t<_AsV>>> using __get_t = conditional_t<is_lvalue_reference_v<_Variant>, _Tp&, _Tp&&>; // Return type of std::visit. template<typename _Visitor, typename... _Variants> using __visit_result_t = invoke_result_t<_Visitor, __get_t<0, _Variants>...>; template<typename _Tp, typename... _Types> constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...); template <typename _Visitor, typename _Variant, size_t... _Idxs> constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>) { return __same_types< invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>... >; } template<size_t _Np, typename _Variant, typename... _Args> inline void __construct_by_index(_Variant& __v, _Args&&... __args) { auto&& __storage = __detail::__variant::__get<_Np>(__v); ::new ((void*)std::addressof(__storage)) remove_reference_t<decltype(__storage)> (std::forward<_Args>(__args)...); // Construction didn't throw, so can set the new index now: __v._M_index = _Np; } } // namespace __variant } // namespace __detail template<typename _Tp, typename... _Types> constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>; } template<typename _Tp, typename... _Types> constexpr _Tp& get(variant<_Types...>& __v) { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); } template<typename _Tp, typename... _Types> constexpr _Tp&& get(variant<_Types...>&& __v) { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( std::move(__v)); } template<typename _Tp, typename... _Types> constexpr const _Tp& get(const variant<_Types...>& __v) { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); } template<typename _Tp, typename... _Types> constexpr const _Tp&& get(const variant<_Types...>&& __v) { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( std::move(__v)); } template<size_t _Np, typename... _Types> constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>> get_if(variant<_Types...>* __ptr) noexcept { using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); if (__ptr && __ptr->index() == _Np) return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); return nullptr; } template<size_t _Np, typename... _Types> constexpr add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>> get_if(const variant<_Types...>* __ptr) noexcept { using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); if (__ptr && __ptr->index() == _Np) return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); return nullptr; } template<typename _Tp, typename... _Types> constexpr add_pointer_t<_Tp> get_if(variant<_Types...>* __ptr) noexcept { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( __ptr); } template<typename _Tp, typename... _Types> constexpr add_pointer_t<const _Tp> get_if(const variant<_Types...>* __ptr) noexcept { static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, "T must occur exactly once in alternatives"); static_assert(!is_void_v<_Tp>, "_Tp must not be void"); return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( __ptr); } struct monostate { }; #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ template<typename... _Types> \ constexpr bool operator __OP(const variant<_Types...>& __lhs, \ const variant<_Types...>& __rhs) \ { \ bool __ret = true; \ __detail::__variant::__raw_idx_visit( \ [&__ret, &__lhs] (auto&& __rhs_mem, auto __rhs_index) mutable \ { \ if constexpr (__rhs_index != variant_npos) \ { \ if (__lhs.index() == __rhs_index) \ { \ auto& __this_mem = std::get<__rhs_index>(__lhs); \ __ret = __this_mem __OP __rhs_mem; \ } \ else \ __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ } \ else \ __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ }, __rhs); \ return __ret; \ } _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) #undef _VARIANT_RELATION_FUNCTION_TEMPLATE constexpr bool operator==(monostate, monostate) noexcept { return true; } #ifdef __cpp_lib_three_way_comparison template<typename... _Types> requires (three_way_comparable<_Types> && ...) constexpr common_comparison_category_t<compare_three_way_result_t<_Types>...> operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w) { common_comparison_category_t<compare_three_way_result_t<_Types>...> __ret = strong_ordering::equal; __detail::__variant::__raw_idx_visit( [&__ret, &__v] (auto&& __w_mem, auto __w_index) mutable { if constexpr (__w_index != variant_npos) { if (__v.index() == __w_index) { auto& __this_mem = std::get<__w_index>(__v); __ret = __this_mem <=> __w_mem; return; } } __ret = (__v.index() + 1) <=> (__w_index + 1); }, __w); return __ret; } constexpr strong_ordering operator<=>(monostate, monostate) noexcept { return strong_ordering::equal; } #else constexpr bool operator!=(monostate, monostate) noexcept { return false; } constexpr bool operator<(monostate, monostate) noexcept { return false; } constexpr bool operator>(monostate, monostate) noexcept { return false; } constexpr bool operator<=(monostate, monostate) noexcept { return true; } constexpr bool operator>=(monostate, monostate) noexcept { return true; } #endif template<typename _Visitor, typename... _Variants> constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> visit(_Visitor&&, _Variants&&...); template<typename... _Types> inline enable_if_t<(is_move_constructible_v<_Types> && ...) && (is_swappable_v<_Types> && ...)> swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs))) { __lhs.swap(__rhs); } template<typename... _Types> enable_if_t<!((is_move_constructible_v<_Types> && ...) && (is_swappable_v<_Types> && ...))> swap(variant<_Types...>&, variant<_Types...>&) = delete; class bad_variant_access : public exception { public: bad_variant_access() noexcept { } const char* what() const noexcept override { return _M_reason; } private: bad_variant_access(const char* __reason) noexcept : _M_reason(__reason) { } // Must point to a string with static storage duration: const char* _M_reason = "bad variant access"; friend void __throw_bad_variant_access(const char* __what); }; // Must only be called with a string literal inline void __throw_bad_variant_access(const char* __what) { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); } inline void __throw_bad_variant_access(bool __valueless) { if (__valueless) [[__unlikely__]] __throw_bad_variant_access("std::get: variant is valueless"); else __throw_bad_variant_access("std::get: wrong index for variant"); } template<typename... _Types> class variant : private __detail::__variant::_Variant_base<_Types...>, private _Enable_default_constructor< __detail::__variant::_Traits<_Types...>::_S_default_ctor, variant<_Types...>>, private _Enable_copy_move< __detail::__variant::_Traits<_Types...>::_S_copy_ctor, __detail::__variant::_Traits<_Types...>::_S_copy_assign, __detail::__variant::_Traits<_Types...>::_S_move_ctor, __detail::__variant::_Traits<_Types...>::_S_move_assign, variant<_Types...>> { private: template <typename... _UTypes, typename _Tp> friend decltype(auto) __variant_cast(_Tp&&); template<size_t _Np, typename _Variant, typename... _Args> friend void __detail::__variant::__construct_by_index(_Variant& __v, _Args&&... __args); static_assert(sizeof...(_Types) > 0, "variant must have at least one alternative"); static_assert(!(std::is_reference_v<_Types> || ...), "variant must have no reference alternative"); static_assert(!(std::is_void_v<_Types> || ...), "variant must have no void alternative"); using _Base = __detail::__variant::_Variant_base<_Types...>; using _Default_ctor_enabler = _Enable_default_constructor< __detail::__variant::_Traits<_Types...>::_S_default_ctor, variant<_Types...>>; template<typename _Tp> static constexpr bool __not_self = !is_same_v<__remove_cvref_t<_Tp>, variant>; template<typename _Tp> static constexpr bool __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; template<typename _Tp> static constexpr size_t __accepted_index = __detail::__variant::__accepted_index<_Tp, variant>::value; template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>> using __to_type = variant_alternative_t<_Np, variant>; template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>> using __accepted_type = __to_type<__accepted_index<_Tp>>; template<typename _Tp> static constexpr size_t __index_of = __detail::__variant::__index_of_v<_Tp, _Types...>; using _Traits = __detail::__variant::_Traits<_Types...>; template<typename _Tp> struct __is_in_place_tag : false_type { }; template<typename _Tp> struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { }; template<size_t _Np> struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { }; template<typename _Tp> static constexpr bool __not_in_place_tag = !__is_in_place_tag<__remove_cvref_t<_Tp>>::value; public: variant() = default; variant(const variant& __rhs) = default; variant(variant&&) = default; variant& operator=(const variant&) = default; variant& operator=(variant&&) = default; ~variant() = default; template<typename _Tp, typename = enable_if_t<sizeof...(_Types) != 0>, typename = enable_if_t<__not_in_place_tag<_Tp>>, typename _Tj = __accepted_type<_Tp&&>, typename = enable_if_t<__exactly_once<_Tj> && is_constructible_v<_Tj, _Tp>>> constexpr variant(_Tp&& __t) noexcept(is_nothrow_constructible_v<_Tj, _Tp>) : variant(in_place_index<__accepted_index<_Tp>>, std::forward<_Tp>(__t)) { } template<typename _Tp, typename... _Args, typename = enable_if_t<__exactly_once<_Tp> && is_constructible_v<_Tp, _Args...>>> constexpr explicit variant(in_place_type_t<_Tp>, _Args&&... __args) : variant(in_place_index<__index_of<_Tp>>, std::forward<_Args>(__args)...) { } template<typename _Tp, typename _Up, typename... _Args, typename = enable_if_t<__exactly_once<_Tp> && is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>>> constexpr explicit variant(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args) : variant(in_place_index<__index_of<_Tp>>, __il, std::forward<_Args>(__args)...) { } template<size_t _Np, typename... _Args, typename _Tp = __to_type<_Np>, typename = enable_if_t<is_constructible_v<_Tp, _Args...>>> constexpr explicit variant(in_place_index_t<_Np>, _Args&&... __args) : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...), _Default_ctor_enabler(_Enable_default_constructor_tag{}) { } template<size_t _Np, typename _Up, typename... _Args, typename _Tp = __to_type<_Np>, typename = enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>>> constexpr explicit variant(in_place_index_t<_Np>, initializer_list<_Up> __il, _Args&&... __args) : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...), _Default_ctor_enabler(_Enable_default_constructor_tag{}) { } template<typename _Tp> enable_if_t<__exactly_once<__accepted_type<_Tp&&>> && is_constructible_v<__accepted_type<_Tp&&>, _Tp> && is_assignable_v<__accepted_type<_Tp&&>&, _Tp>, variant&> operator=(_Tp&& __rhs) noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp> && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>) { constexpr auto __index = __accepted_index<_Tp>; if (index() == __index) std::get<__index>(*this) = std::forward<_Tp>(__rhs); else { using _Tj = __accepted_type<_Tp&&>; if constexpr (is_nothrow_constructible_v<_Tj, _Tp> || !is_nothrow_move_constructible_v<_Tj>) this->emplace<__index>(std::forward<_Tp>(__rhs)); else // _GLIBCXX_RESOLVE_LIB_DEFECTS // 3585. converting assignment with immovable alternative this->emplace<__index>(_Tj(std::forward<_Tp>(__rhs))); } return *this; } template<typename _Tp, typename... _Args> enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>, _Tp&> emplace(_Args&&... __args) { constexpr size_t __index = __index_of<_Tp>; return this->emplace<__index>(std::forward<_Args>(__args)...); } template<typename _Tp, typename _Up, typename... _Args> enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...> && __exactly_once<_Tp>, _Tp&> emplace(initializer_list<_Up> __il, _Args&&... __args) { constexpr size_t __index = __index_of<_Tp>; return this->emplace<__index>(__il, std::forward<_Args>(__args)...); } template<size_t _Np, typename... _Args> enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, _Args...>, variant_alternative_t<_Np, variant>&> emplace(_Args&&... __args) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); using type = variant_alternative_t<_Np, variant>; namespace __variant = std::__detail::__variant; // Provide the strong exception-safety guarantee when possible, // to avoid becoming valueless. if constexpr (is_nothrow_constructible_v<type, _Args...>) { this->_M_reset(); __variant::__construct_by_index<_Np>(*this, std::forward<_Args>(__args)...); } else if constexpr (is_scalar_v<type>) { // This might invoke a potentially-throwing conversion operator: const type __tmp(std::forward<_Args>(__args)...); // But these steps won't throw: this->_M_reset(); __variant::__construct_by_index<_Np>(*this, __tmp); } else if constexpr (__variant::_Never_valueless_alt<type>() && _Traits::_S_move_assign) { // This construction might throw: variant __tmp(in_place_index<_Np>, std::forward<_Args>(__args)...); // But _Never_valueless_alt<type> means this won't: *this = std::move(__tmp); } else { // This case only provides the basic exception-safety guarantee, // i.e. the variant can become valueless. this->_M_reset(); __variant::__construct_by_index<_Np>(*this, std::forward<_Args>(__args)...); } return std::get<_Np>(*this); } template<size_t _Np, typename _Up, typename... _Args> enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, initializer_list<_Up>&, _Args...>, variant_alternative_t<_Np, variant>&> emplace(initializer_list<_Up> __il, _Args&&... __args) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); using type = variant_alternative_t<_Np, variant>; namespace __variant = std::__detail::__variant; // Provide the strong exception-safety guarantee when possible, // to avoid becoming valueless. if constexpr (is_nothrow_constructible_v<type, initializer_list<_Up>&, _Args...>) { this->_M_reset(); __variant::__construct_by_index<_Np>(*this, __il, std::forward<_Args>(__args)...); } else if constexpr (__variant::_Never_valueless_alt<type>() && _Traits::_S_move_assign) { // This construction might throw: variant __tmp(in_place_index<_Np>, __il, std::forward<_Args>(__args)...); // But _Never_valueless_alt<type> means this won't: *this = std::move(__tmp); } else { // This case only provides the basic exception-safety guarantee, // i.e. the variant can become valueless. this->_M_reset(); __variant::__construct_by_index<_Np>(*this, __il, std::forward<_Args>(__args)...); } return std::get<_Np>(*this); } constexpr bool valueless_by_exception() const noexcept { return !this->_M_valid(); } constexpr size_t index() const noexcept { using __index_type = typename _Base::__index_type; if constexpr (__detail::__variant::__never_valueless<_Types...>()) return this->_M_index; else if constexpr (sizeof...(_Types) <= __index_type(-1) / 2) return make_signed_t<__index_type>(this->_M_index); else return size_t(__index_type(this->_M_index + 1)) - 1; } void swap(variant& __rhs) noexcept((__is_nothrow_swappable<_Types>::value && ...) && is_nothrow_move_constructible_v<variant>) { __detail::__variant::__raw_idx_visit( [this, &__rhs](auto&& __rhs_mem, auto __rhs_index) mutable { if constexpr (__rhs_index != variant_npos) { if (this->index() == __rhs_index) { auto& __this_mem = std::get<__rhs_index>(*this); using std::swap; swap(__this_mem, __rhs_mem); } else { if (!this->valueless_by_exception()) [[__likely__]] { auto __tmp(std::move(__rhs_mem)); __rhs = std::move(*this); this->_M_destructive_move(__rhs_index, std::move(__tmp)); } else { this->_M_destructive_move(__rhs_index, std::move(__rhs_mem)); __rhs._M_reset(); } } } else { if (!this->valueless_by_exception()) [[__likely__]] { __rhs = std::move(*this); this->_M_reset(); } } }, __rhs); } private: #if defined(__clang__) && __clang_major__ <= 7 public: using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852 private: #endif template<size_t _Np, typename _Vp> friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v) noexcept; #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \ template<typename... _Tp> \ friend constexpr bool \ operator __OP(const variant<_Tp...>& __lhs, \ const variant<_Tp...>& __rhs); _VARIANT_RELATION_FUNCTION_TEMPLATE(<) _VARIANT_RELATION_FUNCTION_TEMPLATE(<=) _VARIANT_RELATION_FUNCTION_TEMPLATE(==) _VARIANT_RELATION_FUNCTION_TEMPLATE(!=) _VARIANT_RELATION_FUNCTION_TEMPLATE(>=) _VARIANT_RELATION_FUNCTION_TEMPLATE(>) #undef _VARIANT_RELATION_FUNCTION_TEMPLATE }; template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>>& get(variant<_Types...>& __v) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); if (__v.index() != _Np) __throw_bad_variant_access(__v.valueless_by_exception()); return __detail::__variant::__get<_Np>(__v); } template<size_t _Np, typename... _Types> constexpr variant_alternative_t<_Np, variant<_Types...>>&& get(variant<_Types...>&& __v) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); if (__v.index() != _Np) __throw_bad_variant_access(__v.valueless_by_exception()); return __detail::__variant::__get<_Np>(std::move(__v)); } template<size_t _Np, typename... _Types> constexpr const variant_alternative_t<_Np, variant<_Types...>>& get(const variant<_Types...>& __v) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); if (__v.index() != _Np) __throw_bad_variant_access(__v.valueless_by_exception()); return __detail::__variant::__get<_Np>(__v); } template<size_t _Np, typename... _Types> constexpr const variant_alternative_t<_Np, variant<_Types...>>&& get(const variant<_Types...>&& __v) { static_assert(_Np < sizeof...(_Types), "The index must be in [0, number of alternatives)"); if (__v.index() != _Np) __throw_bad_variant_access(__v.valueless_by_exception()); return __detail::__variant::__get<_Np>(std::move(__v)); } /// @cond undocumented template<typename _Result_type, typename _Visitor, typename... _Variants> constexpr decltype(auto) __do_visit(_Visitor&& __visitor, _Variants&&... __variants) { constexpr auto& __vtable = __detail::__variant::__gen_vtable< _Result_type, _Visitor&&, _Variants&&...>::_S_vtable; auto __func_ptr = __vtable._M_access(__variants.index()...); return (*__func_ptr)(std::forward<_Visitor>(__visitor), std::forward<_Variants>(__variants)...); } /// @endcond template<typename _Visitor, typename... _Variants> constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> visit(_Visitor&& __visitor, _Variants&&... __variants) { namespace __variant = std::__detail::__variant; if ((__variant::__as(__variants).valueless_by_exception() || ...)) __throw_bad_variant_access("std::visit: variant is valueless"); using _Result_type = __detail::__variant::__visit_result_t<_Visitor, _Variants...>; using _Tag = __detail::__variant::__deduce_visit_result<_Result_type>; if constexpr (sizeof...(_Variants) == 1) { using _Vp = decltype(__variant::__as(std::declval<_Variants>()...)); constexpr bool __visit_rettypes_match = __detail::__variant:: __check_visitor_results<_Visitor, _Vp>( make_index_sequence<variant_size_v<remove_reference_t<_Vp>>>()); if constexpr (!__visit_rettypes_match) { static_assert(__visit_rettypes_match, "std::visit requires the visitor to have the same " "return type for all alternatives of a variant"); return; } else return std::__do_visit<_Tag>( std::forward<_Visitor>(__visitor), static_cast<_Vp>(__variants)...); } else return std::__do_visit<_Tag>( std::forward<_Visitor>(__visitor), __variant::__as(std::forward<_Variants>(__variants))...); } #if __cplusplus > 201703L template<typename _Res, typename _Visitor, typename... _Variants> constexpr _Res visit(_Visitor&& __visitor, _Variants&&... __variants) { namespace __variant = std::__detail::__variant; if ((__variant::__as(__variants).valueless_by_exception() || ...)) __throw_bad_variant_access("std::visit<R>: variant is valueless"); return std::__do_visit<_Res>(std::forward<_Visitor>(__visitor), __variant::__as(std::forward<_Variants>(__variants))...); } #endif /// @cond undocumented template<bool, typename... _Types> struct __variant_hash_call_base_impl { size_t operator()(const variant<_Types...>& __t) const noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...)) { size_t __ret; __detail::__variant::__raw_visit( [&__t, &__ret](auto&& __t_mem) mutable { using _Type = __remove_cvref_t<decltype(__t_mem)>; if constexpr (!is_same_v<_Type, __detail::__variant::__variant_cookie>) __ret = std::hash<size_t>{}(__t.index()) + std::hash<_Type>{}(__t_mem); else __ret = std::hash<size_t>{}(__t.index()); }, __t); return __ret; } }; template<typename... _Types> struct __variant_hash_call_base_impl<false, _Types...> {}; template<typename... _Types> using __variant_hash_call_base = __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>:: __enable_hash_call &&...), _Types...>; /// @endcond template<typename... _Types> struct hash<variant<_Types...>> : private __detail::__variant::_Variant_hash_base< variant<_Types...>, std::index_sequence_for<_Types...>>, public __variant_hash_call_base<_Types...> { using result_type [[__deprecated__]] = size_t; using argument_type [[__deprecated__]] = variant<_Types...>; }; template<> struct hash<monostate> { using result_type [[__deprecated__]] = size_t; using argument_type [[__deprecated__]] = monostate; size_t operator()(const monostate&) const noexcept { constexpr size_t __magic_monostate_hash = -7777; return __magic_monostate_hash; } }; template<typename... _Types> struct __is_fast_hash<hash<variant<_Types...>>> : bool_constant<(__is_fast_hash<_Types>::value && ...)> { }; _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif // C++17 #endif // _GLIBCXX_VARIANT