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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 //
. /** @file variant * This is the `
` C++ Library header. */ #ifndef _GLIBCXX_VARIANT #define _GLIBCXX_VARIANT 1 #pragma GCC system_header #if __cplusplus >= 201703L #include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#if __cplusplus > 201703L # include
#endif namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace __detail { namespace __variant { template
struct _Nth_type; template
struct _Nth_type<_Np, _First, _Rest...> : _Nth_type<_Np-1, _Rest...> { }; template
struct _Nth_type<0, _First, _Rest...> { using type = _First; }; } // namespace __variant } // namespace __detail #define __cpp_lib_variant 202102L template
class tuple; template
class variant; template
struct hash; template
struct variant_size; template
struct variant_size
: variant_size<_Variant> {}; template
struct variant_size
: variant_size<_Variant> {}; template
struct variant_size
: variant_size<_Variant> {}; template
struct variant_size
> : std::integral_constant
{}; template
inline constexpr size_t variant_size_v = variant_size<_Variant>::value; template
struct variant_alternative; template
struct variant_alternative<_Np, variant<_First, _Rest...>> : variant_alternative<_Np-1, variant<_Rest...>> {}; template
struct variant_alternative<0, variant<_First, _Rest...>> { using type = _First; }; template
using variant_alternative_t = typename variant_alternative<_Np, _Variant>::type; template
struct variant_alternative<_Np, const _Variant> { using type = add_const_t
>; }; template
struct variant_alternative<_Np, volatile _Variant> { using type = add_volatile_t
>; }; template
struct variant_alternative<_Np, const volatile _Variant> { using type = add_cv_t
>; }; inline constexpr size_t variant_npos = -1; template
constexpr variant_alternative_t<_Np, variant<_Types...>>& get(variant<_Types...>&); template
constexpr variant_alternative_t<_Np, variant<_Types...>>&& get(variant<_Types...>&&); template
constexpr variant_alternative_t<_Np, variant<_Types...>> const& get(const variant<_Types...>&); template
constexpr variant_alternative_t<_Np, variant<_Types...>> const&& get(const variant<_Types...>&&); template
constexpr decltype(auto) __do_visit(_Visitor&& __visitor, _Variants&&... __variants); template
decltype(auto) __variant_cast(_Tp&& __rhs) { if constexpr (is_lvalue_reference_v<_Tp>) { if constexpr (is_const_v
>) return static_cast
&>(__rhs); else return static_cast
&>(__rhs); } else return static_cast
&&>(__rhs); } namespace __detail { namespace __variant { // Returns the first appearance of _Tp in _Types. // Returns sizeof...(_Types) if _Tp is not in _Types. template
struct __index_of : std::integral_constant
{}; template
inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value; template
struct __index_of<_Tp, _First, _Rest...> : std::integral_constant
? 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
struct __deduce_visit_result { using type = _Tp; }; // Visit variants that might be valueless. template
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
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
constexpr std::variant<_Types...>& __as(std::variant<_Types...>& __v) noexcept { return __v; } template
constexpr const std::variant<_Types...>& __as(const std::variant<_Types...>& __v) noexcept { return __v; } template
constexpr std::variant<_Types...>&& __as(std::variant<_Types...>&& __v) noexcept { return std::move(__v); } template
constexpr const std::variant<_Types...>&& __as(const std::variant<_Types...>&& __v) noexcept { return std::move(__v); } // _Uninitialized
is guaranteed to be a trivially destructible type, // even if T is not. template
> struct _Uninitialized; template
struct _Uninitialized<_Type, true> { template
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
struct _Uninitialized<_Type, false> { template
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
constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u) noexcept { return std::forward<_Union>(__u)._M_first._M_get(); } template
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
constexpr decltype(auto) __get(_Variant&& __v) noexcept { return __variant::__get(std::in_place_index<_Np>, std::forward<_Variant>(__v)._M_u); } template
struct _Traits { static constexpr bool _S_default_ctor = is_default_constructible_v
::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
union _Variadic_union { }; template
union _Variadic_union<_First, _Rest...> { constexpr _Variadic_union() : _M_rest() { } template
constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args) : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) { } template
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
struct _Never_valueless_alt : __and_
, 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
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
constexpr bool __never_valueless() { return _Traits<_Types...>::_S_move_assign && (_Never_valueless_alt<_Types>::value && ...); } // Defines index and the dtor, possibly trivial. template
struct _Variant_storage; template
using __select_index = typename __select_int::_Select_int_base
::type::value_type; template
struct _Variant_storage
{ constexpr _Variant_storage() : _M_index(static_cast<__index_type>(variant_npos)) { } template
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
([](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
struct _Variant_storage
{ constexpr _Variant_storage() : _M_index(static_cast<__index_type>(variant_npos)) { } template
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
using _Variant_storage_alias = _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; template
void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem) { void* __storage = std::addressof(__lhs._M_u); using _Type = remove_reference_t
; if constexpr (!is_same_v<_Type, __variant_cookie>) ::new (__storage) _Type(std::forward
(__rhs_mem)); } template
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
(__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
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
struct _Copy_ctor_base
: _Variant_storage_alias<_Types...> { using _Base = _Variant_storage_alias<_Types...>; using _Base::_Base; }; template
using _Copy_ctor_alias = _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; template
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
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
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
struct _Move_ctor_base
: _Copy_ctor_alias<_Types...> { using _Base = _Copy_ctor_alias<_Types...>; using _Base::_Base; template
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
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
using _Move_ctor_alias = _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; template
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
; 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
struct _Copy_assign_base
: _Move_ctor_alias<_Types...> { using _Base = _Move_ctor_alias<_Types...>; using _Base::_Base; }; template
using _Copy_assign_alias = _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>; template
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
struct _Move_assign_base
: _Copy_assign_alias<_Types...> { using _Base = _Copy_assign_alias<_Types...>; using _Base::_Base; }; template
using _Move_assign_alias = _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>; template
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
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
struct __tuple_count; template
inline constexpr size_t __tuple_count_v = __tuple_count<_Tp, _Tuple>::value; template
struct __tuple_count<_Tp, tuple<_Types...>> : integral_constant
{ }; template
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
? template
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
struct _Arr { _Ti _M_x[1]; }; // "Build an imaginary function FUN(Ti) for each alternative type Ti" template
struct _Build_FUN { // This function means 'using _Build_FUN
::_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)}; is well-formed." template
struct _Build_FUN<_Ind, _Tp, _Ti, void_t
{{std::declval<_Tp>()}})>> { // This is the FUN function for type _Ti, with index _Ind static integral_constant
_S_fun(_Ti); }; template
>> struct _Build_FUNs; template
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
using _FUN_type = decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>())); // The index selected for FUN(std::forward
(t)), or variant_npos if none. template
struct __accepted_index : integral_constant
{ }; template
struct __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>> : _FUN_type<_Tp, _Variant> { }; template
struct _Extra_visit_slot_needed { template
struct _Variant_never_valueless; template
struct _Variant_never_valueless
> : 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
struct _Multi_array; // Partial specialization with rank zero, stores a single _Tp element. template
struct _Multi_array<_Tp> { template
struct __untag_result : false_type { using element_type = _Tp; }; template
struct __untag_result
: false_type { using element_type = void(*)(_Args...); }; template
struct __untag_result<__variant_cookie(*)(_Args...)> : false_type { using element_type = void(*)(_Args...); }; template
struct __untag_result<__variant_idx_cookie(*)(_Args...)> : false_type { using element_type = void(*)(_Args...); }; template
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
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
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
(), // typedef'ed as V1 // variant
()) // typedef'ed as V2 // will trigger instantiations of: // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<0>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<0, 0>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<0, 1>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<0, 2>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<1>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<1, 0>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<1, 1>> // __gen_vtable_impl<_Multi_array
, // tuple
, std::index_sequence<1, 2>> // The returned multi-dimensional vtable can be fast accessed by the visitor // using index calculation. template
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
struct __gen_vtable_impl< _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, std::index_sequence<__indices...>> { using _Next = remove_reference_t
::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
>()); return __vtable; } template
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
( __vtable._M_arr[__var_indices + 1], &(__vtable._M_arr[0])), ...); else (_S_apply_single_alt
( __vtable._M_arr[__var_indices]), ...); } template
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
, 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
struct __gen_vtable_impl< _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, std::index_sequence<__indices...>> { using _Array_type = _Multi_array<_Result_type (*)(_Visitor, _Variants...)>; template
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
()...); 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
use INVOKE
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
(), 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
struct __gen_vtable { using _Array_type = _Multi_array<_Result_type (*)(_Visitor, _Variants...), variant_size_v
>...>; static constexpr _Array_type _S_vtable = __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply(); }; template
struct _Base_dedup : public _Tp { }; template
struct _Variant_hash_base; template
struct _Variant_hash_base
, std::index_sequence<__indices...>> : _Base_dedup<__indices, __poison_hash
>>... { }; // Equivalent to decltype(get<_Np>(as-variant(declval<_Variant>()))) template
())), typename _Tp = variant_alternative_t<_Np, remove_reference_t<_AsV>>> using __get_t = conditional_t
, _Tp&, _Tp&&>; // Return type of std::visit. template
using __visit_result_t = invoke_result_t<_Visitor, __get_t<0, _Variants>...>; template
constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...); template
constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>) { return __same_types< invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>... >; } template
inline void __construct_by_index(_Variant& __v, _Args&&... __args) { auto&& __storage = __detail::__variant::__get<_Np>(__v); ::new ((void*)std::addressof(__storage)) remove_reference_t
(std::forward<_Args>(__args)...); // Construction didn't throw, so can set the new index now: __v._M_index = _Np; } } // namespace __variant } // namespace __detail template
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
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
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
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
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
constexpr add_pointer_t
>> 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
constexpr add_pointer_t
>> 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
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
constexpr add_pointer_t
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
\ 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
requires (three_way_comparable<_Types> && ...) constexpr common_comparison_category_t
...> operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w) { common_comparison_category_t
...> __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
constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> visit(_Visitor&&, _Variants&&...); template
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
enable_if_t && ...) && (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
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
friend decltype(auto) __variant_cast(_Tp&&); template
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
static constexpr bool __not_self = !is_same_v<__remove_cvref_t<_Tp>, variant>; template
static constexpr bool __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; template
static constexpr size_t __accepted_index = __detail::__variant::__accepted_index<_Tp, variant>::value; template
> using __to_type = variant_alternative_t<_Np, variant>; template
>> using __accepted_type = __to_type<__accepted_index<_Tp>>; template
static constexpr size_t __index_of = __detail::__variant::__index_of_v<_Tp, _Types...>; using _Traits = __detail::__variant::_Traits<_Types...>; template
struct __is_in_place_tag : false_type { }; template
struct __is_in_place_tag
> : true_type { }; template
struct __is_in_place_tag
> : true_type { }; template
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 = 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
&& 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
&& 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
, typename = enable_if_t
>> 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
, typename = enable_if_t
&, _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
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
enable_if_t
&& __exactly_once<_Tp>, _Tp&> emplace(_Args&&... __args) { constexpr size_t __index = __index_of<_Tp>; return this->emplace<__index>(std::forward<_Args>(__args)...); } template
enable_if_t
&, _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