2 //===------------------------------ variant -------------------------------===//
4 // The LLVM Compiler Infrastructure
6 // This file is dual licensed under the MIT and the University of Illinois Open
7 // Source Licenses. See LICENSE.TXT for details.
9 //===----------------------------------------------------------------------===//
11 #ifndef _LIBCPP_VARIANT
12 #define _LIBCPP_VARIANT
19 // 20.7.2, class template variant
20 template <class... Types>
24 // 20.7.2.1, constructors
25 constexpr variant() noexcept(see below);
26 variant(const variant&);
27 variant(variant&&) noexcept(see below);
29 template <class T> constexpr variant(T&&) noexcept(see below);
31 template <class T, class... Args>
32 constexpr explicit variant(in_place_type_t<T>, Args&&...);
34 template <class T, class U, class... Args>
35 constexpr explicit variant(
36 in_place_type_t<T>, initializer_list<U>, Args&&...);
38 template <size_t I, class... Args>
39 constexpr explicit variant(in_place_index_t<I>, Args&&...);
41 template <size_t I, class U, class... Args>
42 constexpr explicit variant(
43 in_place_index_t<I>, initializer_list<U>, Args&&...);
45 // 20.7.2.2, destructor
48 // 20.7.2.3, assignment
49 variant& operator=(const variant&);
50 variant& operator=(variant&&) noexcept(see below);
52 template <class T> variant& operator=(T&&) noexcept(see below);
54 // 20.7.2.4, modifiers
55 template <class T, class... Args>
56 T& emplace(Args&&...);
58 template <class T, class U, class... Args>
59 T& emplace(initializer_list<U>, Args&&...);
61 template <size_t I, class... Args>
62 variant_alternative_t<I, variant>& emplace(Args&&...);
64 template <size_t I, class U, class... Args>
65 variant_alternative_t<I, variant>& emplace(initializer_list<U>, Args&&...);
67 // 20.7.2.5, value status
68 constexpr bool valueless_by_exception() const noexcept;
69 constexpr size_t index() const noexcept;
72 void swap(variant&) noexcept(see below);
75 // 20.7.3, variant helper classes
76 template <class T> struct variant_size; // undefined
79 constexpr size_t variant_size_v = variant_size<T>::value;
81 template <class T> struct variant_size<const T>;
82 template <class T> struct variant_size<volatile T>;
83 template <class T> struct variant_size<const volatile T>;
85 template <class... Types>
86 struct variant_size<variant<Types...>>;
88 template <size_t I, class T> struct variant_alternative; // undefined
90 template <size_t I, class T>
91 using variant_alternative_t = typename variant_alternative<I, T>::type;
93 template <size_t I, class T> struct variant_alternative<I, const T>;
94 template <size_t I, class T> struct variant_alternative<I, volatile T>;
95 template <size_t I, class T> struct variant_alternative<I, const volatile T>;
97 template <size_t I, class... Types>
98 struct variant_alternative<I, variant<Types...>>;
100 constexpr size_t variant_npos = -1;
102 // 20.7.4, value access
103 template <class T, class... Types>
104 constexpr bool holds_alternative(const variant<Types...>&) noexcept;
106 template <size_t I, class... Types>
107 constexpr variant_alternative_t<I, variant<Types...>>&
108 get(variant<Types...>&);
110 template <size_t I, class... Types>
111 constexpr variant_alternative_t<I, variant<Types...>>&&
112 get(variant<Types...>&&);
114 template <size_t I, class... Types>
115 constexpr variant_alternative_t<I, variant<Types...>> const&
116 get(const variant<Types...>&);
118 template <size_t I, class... Types>
119 constexpr variant_alternative_t<I, variant<Types...>> const&&
120 get(const variant<Types...>&&);
122 template <class T, class... Types>
123 constexpr T& get(variant<Types...>&);
125 template <class T, class... Types>
126 constexpr T&& get(variant<Types...>&&);
128 template <class T, class... Types>
129 constexpr const T& get(const variant<Types...>&);
131 template <class T, class... Types>
132 constexpr const T&& get(const variant<Types...>&&);
134 template <size_t I, class... Types>
135 constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
136 get_if(variant<Types...>*) noexcept;
138 template <size_t I, class... Types>
139 constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
140 get_if(const variant<Types...>*) noexcept;
142 template <class T, class... Types>
143 constexpr add_pointer_t<T>
144 get_if(variant<Types...>*) noexcept;
146 template <class T, class... Types>
147 constexpr add_pointer_t<const T>
148 get_if(const variant<Types...>*) noexcept;
150 // 20.7.5, relational operators
151 template <class... Types>
152 constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
154 template <class... Types>
155 constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
157 template <class... Types>
158 constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
160 template <class... Types>
161 constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
163 template <class... Types>
164 constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
166 template <class... Types>
167 constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
169 // 20.7.6, visitation
170 template <class Visitor, class... Variants>
171 constexpr see below visit(Visitor&&, Variants&&...);
173 // 20.7.7, class monostate
176 // 20.7.8, monostate relational operators
177 constexpr bool operator<(monostate, monostate) noexcept;
178 constexpr bool operator>(monostate, monostate) noexcept;
179 constexpr bool operator<=(monostate, monostate) noexcept;
180 constexpr bool operator>=(monostate, monostate) noexcept;
181 constexpr bool operator==(monostate, monostate) noexcept;
182 constexpr bool operator!=(monostate, monostate) noexcept;
184 // 20.7.9, specialized algorithms
185 template <class... Types>
186 void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
188 // 20.7.10, class bad_variant_access
189 class bad_variant_access;
191 // 20.7.11, hash support
192 template <class T> struct hash;
193 template <class... Types> struct hash<variant<Types...>>;
194 template <> struct hash<monostate>;
204 #include <functional>
205 #include <initializer_list>
208 #include <type_traits>
211 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
212 #pragma GCC system_header
215 namespace std { // explicitly not using versioning namespace
217 class _LIBCPP_EXCEPTION_ABI bad_variant_access : public exception {
219 virtual const char* what() const _NOEXCEPT;
224 _LIBCPP_BEGIN_NAMESPACE_STD
226 #if _LIBCPP_STD_VER > 14
229 inline _LIBCPP_INLINE_VISIBILITY
230 void __throw_bad_variant_access() {
231 #ifndef _LIBCPP_NO_EXCEPTIONS
232 throw bad_variant_access();
238 template <class... _Types>
239 class _LIBCPP_TEMPLATE_VIS variant;
242 struct _LIBCPP_TEMPLATE_VIS variant_size;
245 constexpr size_t variant_size_v = variant_size<_Tp>::value;
248 struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
251 struct _LIBCPP_TEMPLATE_VIS variant_size<volatile _Tp> : variant_size<_Tp> {};
254 struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp>
255 : variant_size<_Tp> {};
257 template <class... _Types>
258 struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>>
259 : integral_constant<size_t, sizeof...(_Types)> {};
261 template <size_t _Ip, class _Tp>
262 struct _LIBCPP_TEMPLATE_VIS variant_alternative;
264 template <size_t _Ip, class _Tp>
265 using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
267 template <size_t _Ip, class _Tp>
268 struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const _Tp>
269 : add_const<variant_alternative_t<_Ip, _Tp>> {};
271 template <size_t _Ip, class _Tp>
272 struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, volatile _Tp>
273 : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
275 template <size_t _Ip, class _Tp>
276 struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const volatile _Tp>
277 : add_cv<variant_alternative_t<_Ip, _Tp>> {};
279 template <size_t _Ip, class... _Types>
280 struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
281 static_assert(_Ip < sizeof...(_Types));
282 using type = __type_pack_element<_Ip, _Types...>;
285 constexpr size_t variant_npos = static_cast<size_t>(-1);
286 constexpr unsigned int __variant_npos = static_cast<unsigned int>(-1);
288 namespace __find_detail {
290 template <class _Tp, class... _Types>
291 inline _LIBCPP_INLINE_VISIBILITY
292 constexpr size_t __find_index() {
293 constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
294 size_t __result = __not_found;
295 for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
296 if (__matches[__i]) {
297 if (__result != __not_found) {
306 template <size_t _Index>
307 struct __find_unambiguous_index_sfinae_impl
308 : integral_constant<size_t, _Index> {};
311 struct __find_unambiguous_index_sfinae_impl<__not_found> {};
314 struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
316 template <class _Tp, class... _Types>
317 struct __find_unambiguous_index_sfinae
318 : __find_unambiguous_index_sfinae_impl<__find_index<_Tp, _Types...>()> {};
320 } // namespace __find_detail
322 namespace __variant_detail {
324 struct __valueless_t {};
326 enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
328 template <typename _Tp,
329 template <typename> class _IsTriviallyAvailable,
330 template <typename> class _IsAvailable>
331 constexpr _Trait __trait =
332 _IsTriviallyAvailable<_Tp>::value
333 ? _Trait::_TriviallyAvailable
334 : _IsAvailable<_Tp>::value ? _Trait::_Available : _Trait::_Unavailable;
336 inline _LIBCPP_INLINE_VISIBILITY
337 constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
338 _Trait __result = _Trait::_TriviallyAvailable;
339 for (_Trait __t : __traits) {
340 if (static_cast<int>(__t) > static_cast<int>(__result)) {
347 template <typename... _Types>
349 static constexpr _Trait __copy_constructible_trait =
350 __common_trait({__trait<_Types,
351 is_trivially_copy_constructible,
352 is_copy_constructible>...});
354 static constexpr _Trait __move_constructible_trait =
355 __common_trait({__trait<_Types,
356 is_trivially_move_constructible,
357 is_move_constructible>...});
359 static constexpr _Trait __copy_assignable_trait = __common_trait(
360 {__copy_constructible_trait,
361 __move_constructible_trait,
362 __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
364 static constexpr _Trait __move_assignable_trait = __common_trait(
365 {__move_constructible_trait,
366 __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
368 static constexpr _Trait __destructible_trait = __common_trait(
369 {__trait<_Types, is_trivially_destructible, is_destructible>...});
376 inline _LIBCPP_INLINE_VISIBILITY
377 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
378 return _VSTD::forward<_Vp>(__v).__head;
381 template <class _Vp, size_t _Ip>
382 inline _LIBCPP_INLINE_VISIBILITY
383 static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
384 return __get_alt(_VSTD::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
389 template <size_t _Ip, class _Vp>
390 inline _LIBCPP_INLINE_VISIBILITY
391 static constexpr auto&& __get_alt(_Vp&& __v) {
392 return __union::__get_alt(_VSTD::forward<_Vp>(__v).__data,
393 in_place_index<_Ip>);
398 template <size_t _Ip, class _Vp>
399 inline _LIBCPP_INLINE_VISIBILITY
400 static constexpr auto&& __get_alt(_Vp&& __v) {
401 return __base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v).__impl);
405 } // namespace __access
407 namespace __visitation {
410 template <class _Visitor, class... _Vs>
411 inline _LIBCPP_INLINE_VISIBILITY
412 static constexpr decltype(auto)
413 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
414 constexpr auto __fdiagonal =
415 __make_fdiagonal<_Visitor&&,
416 decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
417 return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
418 _VSTD::forward<_Vs>(__vs).__as_base()...);
421 template <class _Visitor, class... _Vs>
422 inline _LIBCPP_INLINE_VISIBILITY
423 static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
425 constexpr auto __fmatrix =
426 __make_fmatrix<_Visitor&&,
427 decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
428 const size_t __indices[] = {__vs.index()...};
429 return __at(__fmatrix, __indices)(_VSTD::forward<_Visitor>(__visitor),
430 _VSTD::forward<_Vs>(__vs).__as_base()...);
435 inline _LIBCPP_INLINE_VISIBILITY
436 static constexpr const _Tp& __at_impl(const _Tp& __elem, const size_t*) {
440 template <class _Tp, size_t _Np>
441 inline _LIBCPP_INLINE_VISIBILITY
442 static constexpr auto&& __at_impl(const array<_Tp, _Np>& __elems,
443 const size_t* __index) {
444 return __at_impl(__elems[*__index], __index + 1);
447 template <class _Tp, size_t _Np, size_t _Ip>
448 inline _LIBCPP_INLINE_VISIBILITY
449 static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
450 const size_t (&__indices)[_Ip]) {
451 return __at_impl(__elems, begin(__indices));
454 template <class _Fp, class... _Fs>
455 static constexpr void __std_visit_visitor_return_type_check() {
457 __all<is_same_v<_Fp, _Fs>...>::value,
458 "`std::visit` requires the visitor to have a single return type.");
461 template <class... _Fs>
462 inline _LIBCPP_INLINE_VISIBILITY
463 static constexpr auto __make_farray(_Fs&&... __fs) {
464 __std_visit_visitor_return_type_check<decay_t<_Fs>...>();
465 using __result = array<common_type_t<decay_t<_Fs>...>, sizeof...(_Fs)>;
466 return __result{{_VSTD::forward<_Fs>(__fs)...}};
469 template <std::size_t... _Is>
470 struct __dispatcher {
471 template <class _Fp, class... _Vs>
472 inline _LIBCPP_INLINE_VISIBILITY
473 static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
474 return __invoke_constexpr(
475 static_cast<_Fp>(__f),
476 __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
480 template <class _Fp, class... _Vs, size_t... _Is>
481 inline _LIBCPP_INLINE_VISIBILITY
482 static constexpr auto __make_dispatch(index_sequence<_Is...>) {
483 return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
486 template <size_t _Ip, class _Fp, class... _Vs>
487 inline _LIBCPP_INLINE_VISIBILITY
488 static constexpr auto __make_fdiagonal_impl() {
489 return __make_dispatch<_Fp, _Vs...>(
490 index_sequence<(__identity<_Vs>{}, _Ip)...>{});
493 template <class _Fp, class... _Vs, size_t... _Is>
494 inline _LIBCPP_INLINE_VISIBILITY
495 static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
496 return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
499 template <class _Fp, class _Vp, class... _Vs>
500 inline _LIBCPP_INLINE_VISIBILITY
501 static constexpr auto __make_fdiagonal() {
502 constexpr size_t _Np = decay_t<_Vp>::__size();
503 static_assert(__all<(_Np == decay_t<_Vs>::__size())...>::value);
504 return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
507 template <class _Fp, class... _Vs, size_t... _Is>
508 inline _LIBCPP_INLINE_VISIBILITY
509 static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
510 return __make_dispatch<_Fp, _Vs...>(__is);
513 template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
514 inline _LIBCPP_INLINE_VISIBILITY
515 static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
516 index_sequence<_Js...>,
518 return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
519 index_sequence<_Is..., _Js>{}, __ls...)...);
522 template <class _Fp, class... _Vs>
523 inline _LIBCPP_INLINE_VISIBILITY
524 static constexpr auto __make_fmatrix() {
525 return __make_fmatrix_impl<_Fp, _Vs...>(
526 index_sequence<>{}, make_index_sequence<decay_t<_Vs>::__size()>{}...);
531 template <class _Visitor, class... _Vs>
532 inline _LIBCPP_INLINE_VISIBILITY
533 static constexpr decltype(auto)
534 __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
535 return __base::__visit_alt_at(__index,
536 _VSTD::forward<_Visitor>(__visitor),
537 _VSTD::forward<_Vs>(__vs).__impl...);
540 template <class _Visitor, class... _Vs>
541 inline _LIBCPP_INLINE_VISIBILITY
542 static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
544 return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
545 _VSTD::forward<_Vs>(__vs).__impl...);
548 template <class _Visitor, class... _Vs>
549 inline _LIBCPP_INLINE_VISIBILITY
550 static constexpr decltype(auto)
551 __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
552 return __visit_alt_at(
554 __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
555 _VSTD::forward<_Vs>(__vs)...);
558 template <class _Visitor, class... _Vs>
559 inline _LIBCPP_INLINE_VISIBILITY
560 static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
563 __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
564 _VSTD::forward<_Vs>(__vs)...);
568 template <class _Visitor, class... _Values>
569 static constexpr void __std_visit_exhaustive_visitor_check() {
570 static_assert(is_callable_v<_Visitor(_Values...)>,
571 "`std::visit` requires the visitor to be exhaustive.");
574 template <class _Visitor>
575 struct __value_visitor {
576 template <class... _Alts>
577 inline _LIBCPP_INLINE_VISIBILITY
578 constexpr decltype(auto) operator()(_Alts&&... __alts) const {
579 __std_visit_exhaustive_visitor_check<
581 decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
582 return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
583 _VSTD::forward<_Alts>(__alts).__value...);
585 _Visitor&& __visitor;
588 template <class _Visitor>
589 inline _LIBCPP_INLINE_VISIBILITY
590 static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
591 return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
595 } // namespace __visitation
597 template <size_t _Index, class _Tp>
598 struct _LIBCPP_TEMPLATE_VIS __alt {
599 using __value_type = _Tp;
601 template <class... _Args>
602 inline _LIBCPP_INLINE_VISIBILITY
603 explicit constexpr __alt(in_place_t, _Args&&... __args)
604 : __value(_VSTD::forward<_Args>(__args)...) {}
606 __value_type __value;
609 template <_Trait _DestructibleTrait, size_t _Index, class... _Types>
610 union _LIBCPP_TEMPLATE_VIS __union;
612 template <_Trait _DestructibleTrait, size_t _Index>
613 union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {};
615 #define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
616 template <size_t _Index, class _Tp, class... _Types> \
617 union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
622 inline _LIBCPP_INLINE_VISIBILITY \
623 explicit constexpr __union(__valueless_t) noexcept : __dummy{} {} \
625 template <class... _Args> \
626 inline _LIBCPP_INLINE_VISIBILITY \
627 explicit constexpr __union(in_place_index_t<0>, _Args&&... __args) \
628 : __head(in_place, _VSTD::forward<_Args>(__args)...) {} \
630 template <size_t _Ip, class... _Args> \
631 inline _LIBCPP_INLINE_VISIBILITY \
632 explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args) \
633 : __tail(in_place_index<_Ip - 1>, _VSTD::forward<_Args>(__args)...) {} \
635 __union(const __union&) = default; \
636 __union(__union&&) = default; \
640 __union& operator=(const __union&) = default; \
641 __union& operator=(__union&&) = default; \
645 __alt<_Index, _Tp> __head; \
646 __union<destructible_trait, _Index + 1, _Types...> __tail; \
648 friend struct __access::__union; \
651 _LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable, ~__union() = default;);
652 _LIBCPP_VARIANT_UNION(_Trait::_Available, ~__union() {});
653 _LIBCPP_VARIANT_UNION(_Trait::_Unavailable, ~__union() = delete;);
655 #undef _LIBCPP_VARIANT_UNION
657 template <_Trait _DestructibleTrait, class... _Types>
658 class _LIBCPP_TEMPLATE_VIS __base {
660 inline _LIBCPP_INLINE_VISIBILITY
661 explicit constexpr __base(__valueless_t tag) noexcept
662 : __data(tag), __index(__variant_npos) {}
664 template <size_t _Ip, class... _Args>
665 inline _LIBCPP_INLINE_VISIBILITY
666 explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
668 __data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...),
671 inline _LIBCPP_INLINE_VISIBILITY
672 constexpr bool valueless_by_exception() const noexcept {
673 return index() == variant_npos;
676 inline _LIBCPP_INLINE_VISIBILITY
677 constexpr size_t index() const noexcept {
678 return __index == __variant_npos ? variant_npos : __index;
682 inline _LIBCPP_INLINE_VISIBILITY
683 constexpr auto&& __as_base() & { return *this; }
685 inline _LIBCPP_INLINE_VISIBILITY
686 constexpr auto&& __as_base() && { return _VSTD::move(*this); }
688 inline _LIBCPP_INLINE_VISIBILITY
689 constexpr auto&& __as_base() const & { return *this; }
691 inline _LIBCPP_INLINE_VISIBILITY
692 constexpr auto&& __as_base() const && { return _VSTD::move(*this); }
694 inline _LIBCPP_INLINE_VISIBILITY
695 static constexpr size_t __size() { return sizeof...(_Types); }
697 __union<_DestructibleTrait, 0, _Types...> __data;
698 unsigned int __index;
700 friend struct __access::__base;
701 friend struct __visitation::__base;
704 template <class _Traits, _Trait = _Traits::__destructible_trait>
705 class _LIBCPP_TEMPLATE_VIS __destructor;
707 #define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy) \
708 template <class... _Types> \
709 class _LIBCPP_TEMPLATE_VIS __destructor<__traits<_Types...>, \
710 destructible_trait> \
711 : public __base<destructible_trait, _Types...> { \
712 using __base_type = __base<destructible_trait, _Types...>; \
715 using __base_type::__base_type; \
716 using __base_type::operator=; \
718 __destructor(const __destructor&) = default; \
719 __destructor(__destructor&&) = default; \
721 __destructor& operator=(const __destructor&) = default; \
722 __destructor& operator=(__destructor&&) = default; \
725 inline _LIBCPP_INLINE_VISIBILITY \
729 _LIBCPP_VARIANT_DESTRUCTOR(
730 _Trait::_TriviallyAvailable,
731 ~__destructor() = default;,
732 void __destroy() noexcept { this->__index = __variant_npos; });
734 _LIBCPP_VARIANT_DESTRUCTOR(
736 ~__destructor() { __destroy(); },
737 void __destroy() noexcept {
738 if (!this->valueless_by_exception()) {
739 __visitation::__base::__visit_alt(
740 [](auto& __alt) noexcept {
741 using __alt_type = decay_t<decltype(__alt)>;
746 this->__index = __variant_npos;
749 _LIBCPP_VARIANT_DESTRUCTOR(
750 _Trait::_Unavailable,
751 ~__destructor() = delete;,
752 void __destroy() noexcept = delete;);
754 #undef _LIBCPP_VARIANT_DESTRUCTOR
756 template <class _Traits>
757 class _LIBCPP_TEMPLATE_VIS __constructor : public __destructor<_Traits> {
758 using __base_type = __destructor<_Traits>;
761 using __base_type::__base_type;
762 using __base_type::operator=;
765 template <size_t _Ip, class _Tp, class... _Args>
766 inline _LIBCPP_INLINE_VISIBILITY
767 static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
768 ::new ((void*)_VSTD::addressof(__a))
769 __alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
773 template <class _Rhs>
774 inline _LIBCPP_INLINE_VISIBILITY
775 static void __generic_construct(__constructor& __lhs, _Rhs&& __rhs) {
777 if (!__rhs.valueless_by_exception()) {
778 __visitation::__base::__visit_alt_at(
780 [](auto& __lhs_alt, auto&& __rhs_alt) {
783 _VSTD::forward<decltype(__rhs_alt)>(__rhs_alt).__value);
785 __lhs, _VSTD::forward<_Rhs>(__rhs));
786 __lhs.__index = __rhs.index();
791 template <class _Traits, _Trait = _Traits::__move_constructible_trait>
792 class _LIBCPP_TEMPLATE_VIS __move_constructor;
794 #define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
796 template <class... _Types> \
797 class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
798 move_constructible_trait> \
799 : public __constructor<__traits<_Types...>> { \
800 using __base_type = __constructor<__traits<_Types...>>; \
803 using __base_type::__base_type; \
804 using __base_type::operator=; \
806 __move_constructor(const __move_constructor&) = default; \
808 ~__move_constructor() = default; \
809 __move_constructor& operator=(const __move_constructor&) = default; \
810 __move_constructor& operator=(__move_constructor&&) = default; \
813 _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
814 _Trait::_TriviallyAvailable,
815 __move_constructor(__move_constructor&& __that) = default;);
817 _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
819 __move_constructor(__move_constructor&& __that) noexcept(
820 __all<is_nothrow_move_constructible_v<_Types>...>::value)
821 : __move_constructor(__valueless_t{}) {
822 this->__generic_construct(*this, _VSTD::move(__that));
825 _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
826 _Trait::_Unavailable,
827 __move_constructor(__move_constructor&&) = delete;);
829 #undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR
831 template <class _Traits, _Trait = _Traits::__copy_constructible_trait>
832 class _LIBCPP_TEMPLATE_VIS __copy_constructor;
834 #define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
836 template <class... _Types> \
837 class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
838 copy_constructible_trait> \
839 : public __move_constructor<__traits<_Types...>> { \
840 using __base_type = __move_constructor<__traits<_Types...>>; \
843 using __base_type::__base_type; \
844 using __base_type::operator=; \
847 __copy_constructor(__copy_constructor&&) = default; \
848 ~__copy_constructor() = default; \
849 __copy_constructor& operator=(const __copy_constructor&) = default; \
850 __copy_constructor& operator=(__copy_constructor&&) = default; \
853 _LIBCPP_VARIANT_COPY_CONSTRUCTOR(
854 _Trait::_TriviallyAvailable,
855 __copy_constructor(const __copy_constructor& __that) = default;);
857 _LIBCPP_VARIANT_COPY_CONSTRUCTOR(
859 __copy_constructor(const __copy_constructor& __that)
860 : __copy_constructor(__valueless_t{}) {
861 this->__generic_construct(*this, __that);
864 _LIBCPP_VARIANT_COPY_CONSTRUCTOR(
865 _Trait::_Unavailable,
866 __copy_constructor(const __copy_constructor&) = delete;);
868 #undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR
870 template <class _Traits>
871 class _LIBCPP_TEMPLATE_VIS __assignment : public __copy_constructor<_Traits> {
872 using __base_type = __copy_constructor<_Traits>;
875 using __base_type::__base_type;
876 using __base_type::operator=;
878 template <size_t _Ip, class... _Args>
879 inline _LIBCPP_INLINE_VISIBILITY
880 auto& __emplace(_Args&&... __args) {
882 auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
883 _VSTD::forward<_Args>(__args)...);
889 template <bool _CopyAssign, size_t _Ip, class _Tp, class _Arg>
890 inline _LIBCPP_INLINE_VISIBILITY
891 void __assign_alt(__alt<_Ip, _Tp>& __a,
893 bool_constant<_CopyAssign> __tag) {
894 if (this->index() == _Ip) {
895 __a.__value = _VSTD::forward<_Arg>(__arg);
898 void operator()(true_type) const {
899 __this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg)));
901 void operator()(false_type) const {
902 __this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg));
904 __assignment* __this;
906 } __impl{this, _VSTD::forward<_Arg>(__arg)};
911 template <class _That>
912 inline _LIBCPP_INLINE_VISIBILITY
913 void __generic_assign(_That&& __that) {
914 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
916 } else if (__that.valueless_by_exception()) {
919 __visitation::__base::__visit_alt_at(
921 [this](auto& __this_alt, auto&& __that_alt) {
924 _VSTD::forward<decltype(__that_alt)>(__that_alt).__value,
925 is_lvalue_reference<_That>{});
927 *this, _VSTD::forward<_That>(__that));
932 template <class _Traits, _Trait = _Traits::__move_assignable_trait>
933 class _LIBCPP_TEMPLATE_VIS __move_assignment;
935 #define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
937 template <class... _Types> \
938 class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
939 move_assignable_trait> \
940 : public __assignment<__traits<_Types...>> { \
941 using __base_type = __assignment<__traits<_Types...>>; \
944 using __base_type::__base_type; \
945 using __base_type::operator=; \
947 __move_assignment(const __move_assignment&) = default; \
948 __move_assignment(__move_assignment&&) = default; \
949 ~__move_assignment() = default; \
950 __move_assignment& operator=(const __move_assignment&) = default; \
954 _LIBCPP_VARIANT_MOVE_ASSIGNMENT(
955 _Trait::_TriviallyAvailable,
956 __move_assignment& operator=(__move_assignment&& __that) = default;);
958 _LIBCPP_VARIANT_MOVE_ASSIGNMENT(
960 __move_assignment& operator=(__move_assignment&& __that) noexcept(
961 __all<(is_nothrow_move_constructible_v<_Types> &&
962 is_nothrow_move_assignable_v<_Types>)...>::value) {
963 this->__generic_assign(_VSTD::move(__that));
967 _LIBCPP_VARIANT_MOVE_ASSIGNMENT(
968 _Trait::_Unavailable,
969 __move_assignment& operator=(__move_assignment&&) = delete;);
971 #undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
973 template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
974 class _LIBCPP_TEMPLATE_VIS __copy_assignment;
976 #define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
978 template <class... _Types> \
979 class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
980 copy_assignable_trait> \
981 : public __move_assignment<__traits<_Types...>> { \
982 using __base_type = __move_assignment<__traits<_Types...>>; \
985 using __base_type::__base_type; \
986 using __base_type::operator=; \
988 __copy_assignment(const __copy_assignment&) = default; \
989 __copy_assignment(__copy_assignment&&) = default; \
990 ~__copy_assignment() = default; \
992 __copy_assignment& operator=(__copy_assignment&&) = default; \
995 _LIBCPP_VARIANT_COPY_ASSIGNMENT(
996 _Trait::_TriviallyAvailable,
997 __copy_assignment& operator=(const __copy_assignment& __that) = default;);
999 _LIBCPP_VARIANT_COPY_ASSIGNMENT(
1001 __copy_assignment& operator=(const __copy_assignment& __that) {
1002 this->__generic_assign(__that);
1006 _LIBCPP_VARIANT_COPY_ASSIGNMENT(
1007 _Trait::_Unavailable,
1008 __copy_assignment& operator=(const __copy_assignment&) = delete;);
1010 #undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
1012 template <class... _Types>
1013 class _LIBCPP_TEMPLATE_VIS __impl
1014 : public __copy_assignment<__traits<_Types...>> {
1015 using __base_type = __copy_assignment<__traits<_Types...>>;
1018 using __base_type::__base_type;
1019 using __base_type::operator=;
1021 template <size_t _Ip, class _Arg>
1022 inline _LIBCPP_INLINE_VISIBILITY
1023 void __assign(_Arg&& __arg) {
1024 this->__assign_alt(__access::__base::__get_alt<_Ip>(*this),
1025 _VSTD::forward<_Arg>(__arg),
1029 inline _LIBCPP_INLINE_VISIBILITY
1030 void __swap(__impl& __that) {
1031 if (this->valueless_by_exception() && __that.valueless_by_exception()) {
1033 } else if (this->index() == __that.index()) {
1034 __visitation::__base::__visit_alt_at(
1036 [](auto& __this_alt, auto& __that_alt) {
1038 swap(__this_alt.__value, __that_alt.__value);
1043 __impl* __lhs = this;
1044 __impl* __rhs = _VSTD::addressof(__that);
1045 if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
1046 _VSTD::swap(__lhs, __rhs);
1048 __impl __tmp(_VSTD::move(*__rhs));
1049 #ifndef _LIBCPP_NO_EXCEPTIONS
1050 // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
1051 // and `__tmp` is nothrow move constructible then we move `__tmp` back
1052 // into `__rhs` and provide the strong exception safety guarentee.
1054 this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
1056 if (__tmp.__move_nothrow()) {
1057 this->__generic_construct(*__rhs, _VSTD::move(__tmp));
1062 this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
1064 this->__generic_construct(*__lhs, _VSTD::move(__tmp));
1069 inline _LIBCPP_INLINE_VISIBILITY
1070 bool __move_nothrow() const {
1071 constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
1072 return this->valueless_by_exception() || __results[this->index()];
1076 template <class... _Types>
1080 struct __overload<> { void operator()() const; };
1082 template <class _Tp, class... _Types>
1083 struct __overload<_Tp, _Types...> : __overload<_Types...> {
1084 using __overload<_Types...>::operator();
1085 __identity<_Tp> operator()(_Tp) const;
1088 template <class _Tp, class... _Types>
1089 using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type;
1091 } // __variant_detail
1093 template <class... _Types>
1094 class _LIBCPP_TEMPLATE_VIS variant
1095 : private __sfinae_ctor_base<
1096 __all<is_copy_constructible_v<_Types>...>::value,
1097 __all<is_move_constructible_v<_Types>...>::value>,
1098 private __sfinae_assign_base<
1099 __all<(is_copy_constructible_v<_Types> &&
1100 is_move_constructible_v<_Types> &&
1101 is_copy_assignable_v<_Types>)...>::value,
1102 __all<(is_move_constructible_v<_Types> &&
1103 is_move_assignable_v<_Types>)...>::value> {
1104 static_assert(0 < sizeof...(_Types),
1105 "variant must consist of at least one alternative.");
1107 static_assert(__all<!is_array_v<_Types>...>::value,
1108 "variant can not have an array type as an alternative.");
1110 static_assert(__all<!is_reference_v<_Types>...>::value,
1111 "variant can not have a reference type as an alternative.");
1113 static_assert(__all<!is_void_v<_Types>...>::value,
1114 "variant can not have a void type as an alternative.");
1116 using __first_type = variant_alternative_t<0, variant>;
1119 template <bool _Dummy = true,
1120 enable_if_t<__dependent_type<is_default_constructible<__first_type>,
1123 inline _LIBCPP_INLINE_VISIBILITY
1124 constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
1125 : __impl(in_place_index<0>) {}
1127 variant(const variant&) = default;
1128 variant(variant&&) = default;
1132 enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
1133 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1135 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1136 enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
1137 inline _LIBCPP_INLINE_VISIBILITY
1138 constexpr variant(_Arg&& __arg) noexcept(
1139 is_nothrow_constructible_v<_Tp, _Arg>)
1140 : __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {}
1142 template <size_t _Ip, class... _Args,
1143 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1144 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1145 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1146 inline _LIBCPP_INLINE_VISIBILITY
1147 explicit constexpr variant(
1148 in_place_index_t<_Ip>,
1149 _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
1150 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
1156 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1157 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1158 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1160 inline _LIBCPP_INLINE_VISIBILITY
1161 explicit constexpr variant(
1162 in_place_index_t<_Ip>,
1163 initializer_list<_Up> __il,
1164 _Args&&... __args) noexcept(
1165 is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1166 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
1172 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1173 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1174 inline _LIBCPP_INLINE_VISIBILITY
1175 explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
1176 is_nothrow_constructible_v<_Tp, _Args...>)
1177 : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
1184 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1185 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1187 inline _LIBCPP_INLINE_VISIBILITY
1188 explicit constexpr variant(
1189 in_place_type_t<_Tp>,
1190 initializer_list<_Up> __il,
1191 _Args&&... __args) noexcept(
1192 is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
1193 : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
1195 ~variant() = default;
1197 variant& operator=(const variant&) = default;
1198 variant& operator=(variant&&) = default;
1202 enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
1203 class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
1205 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1206 enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>,
1208 inline _LIBCPP_INLINE_VISIBILITY
1209 variant& operator=(_Arg&& __arg) noexcept(
1210 is_nothrow_assignable_v<_Tp&, _Arg> &&
1211 is_nothrow_constructible_v<_Tp, _Arg>) {
1212 __impl.template __assign<_Ip>(_VSTD::forward<_Arg>(__arg));
1219 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1220 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1221 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1222 inline _LIBCPP_INLINE_VISIBILITY
1223 _Tp& emplace(_Args&&... __args) {
1224 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
1231 enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
1232 class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
1233 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1235 inline _LIBCPP_INLINE_VISIBILITY
1236 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1237 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
1244 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1245 enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
1246 inline _LIBCPP_INLINE_VISIBILITY
1247 _Tp& emplace(_Args&&... __args) {
1248 return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
1256 __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
1257 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1259 inline _LIBCPP_INLINE_VISIBILITY
1260 _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
1261 return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
1264 inline _LIBCPP_INLINE_VISIBILITY
1265 constexpr bool valueless_by_exception() const noexcept {
1266 return __impl.valueless_by_exception();
1269 inline _LIBCPP_INLINE_VISIBILITY
1270 constexpr size_t index() const noexcept { return __impl.index(); }
1276 __dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
1277 __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
1279 inline _LIBCPP_INLINE_VISIBILITY
1280 void swap(variant& __that) noexcept(
1281 __all<(is_nothrow_move_constructible_v<_Types> &&
1282 is_nothrow_swappable_v<_Types>)...>::value) {
1283 __impl.__swap(__that.__impl);
1287 __variant_detail::__impl<_Types...> __impl;
1289 friend struct __variant_detail::__access::__variant;
1290 friend struct __variant_detail::__visitation::__variant;
1293 template <size_t _Ip, class... _Types>
1294 inline _LIBCPP_INLINE_VISIBILITY
1295 constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
1296 return __v.index() == _Ip;
1299 template <class _Tp, class... _Types>
1300 inline _LIBCPP_INLINE_VISIBILITY
1301 constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
1302 return __holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1305 template <size_t _Ip, class _Vp>
1306 inline _LIBCPP_INLINE_VISIBILITY
1307 static constexpr auto&& __generic_get(_Vp&& __v) {
1308 using __variant_detail::__access::__variant;
1309 if (!__holds_alternative<_Ip>(__v)) {
1310 __throw_bad_variant_access();
1312 return __variant::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)).__value;
1315 template <size_t _Ip, class... _Types>
1316 inline _LIBCPP_INLINE_VISIBILITY
1317 constexpr variant_alternative_t<_Ip, variant<_Types...>>& get(
1318 variant<_Types...>& __v) {
1319 static_assert(_Ip < sizeof...(_Types));
1320 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1321 return __generic_get<_Ip>(__v);
1324 template <size_t _Ip, class... _Types>
1325 inline _LIBCPP_INLINE_VISIBILITY
1326 constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get(
1327 variant<_Types...>&& __v) {
1328 static_assert(_Ip < sizeof...(_Types));
1329 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1330 return __generic_get<_Ip>(_VSTD::move(__v));
1333 template <size_t _Ip, class... _Types>
1334 inline _LIBCPP_INLINE_VISIBILITY
1335 constexpr const variant_alternative_t<_Ip, variant<_Types...>>& get(
1336 const variant<_Types...>& __v) {
1337 static_assert(_Ip < sizeof...(_Types));
1338 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1339 return __generic_get<_Ip>(__v);
1342 template <size_t _Ip, class... _Types>
1343 inline _LIBCPP_INLINE_VISIBILITY
1344 constexpr const variant_alternative_t<_Ip, variant<_Types...>>&& get(
1345 const variant<_Types...>&& __v) {
1346 static_assert(_Ip < sizeof...(_Types));
1347 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1348 return __generic_get<_Ip>(_VSTD::move(__v));
1351 template <class _Tp, class... _Types>
1352 inline _LIBCPP_INLINE_VISIBILITY
1353 constexpr _Tp& get(variant<_Types...>& __v) {
1354 static_assert(!is_void_v<_Tp>);
1355 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1358 template <class _Tp, class... _Types>
1359 inline _LIBCPP_INLINE_VISIBILITY
1360 constexpr _Tp&& get(variant<_Types...>&& __v) {
1361 static_assert(!is_void_v<_Tp>);
1362 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
1366 template <class _Tp, class... _Types>
1367 inline _LIBCPP_INLINE_VISIBILITY
1368 constexpr const _Tp& get(const variant<_Types...>& __v) {
1369 static_assert(!is_void_v<_Tp>);
1370 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1373 template <class _Tp, class... _Types>
1374 inline _LIBCPP_INLINE_VISIBILITY
1375 constexpr const _Tp&& get(const variant<_Types...>&& __v) {
1376 static_assert(!is_void_v<_Tp>);
1377 return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
1381 template <size_t _Ip, class _Vp>
1382 inline _LIBCPP_INLINE_VISIBILITY
1383 constexpr auto* __generic_get_if(_Vp* __v) noexcept {
1384 using __variant_detail::__access::__variant;
1385 return __v && __holds_alternative<_Ip>(*__v)
1386 ? _VSTD::addressof(__variant::__get_alt<_Ip>(*__v).__value)
1390 template <size_t _Ip, class... _Types>
1391 inline _LIBCPP_INLINE_VISIBILITY
1392 constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
1393 get_if(variant<_Types...>* __v) noexcept {
1394 static_assert(_Ip < sizeof...(_Types));
1395 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1396 return __generic_get_if<_Ip>(__v);
1399 template <size_t _Ip, class... _Types>
1400 inline _LIBCPP_INLINE_VISIBILITY
1401 constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
1402 get_if(const variant<_Types...>* __v) noexcept {
1403 static_assert(_Ip < sizeof...(_Types));
1404 static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
1405 return __generic_get_if<_Ip>(__v);
1408 template <class _Tp, class... _Types>
1409 inline _LIBCPP_INLINE_VISIBILITY
1410 constexpr add_pointer_t<_Tp>
1411 get_if(variant<_Types...>* __v) noexcept {
1412 static_assert(!is_void_v<_Tp>);
1413 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1416 template <class _Tp, class... _Types>
1417 inline _LIBCPP_INLINE_VISIBILITY
1418 constexpr add_pointer_t<const _Tp>
1419 get_if(const variant<_Types...>* __v) noexcept {
1420 static_assert(!is_void_v<_Tp>);
1421 return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
1424 template <class... _Types>
1425 inline _LIBCPP_INLINE_VISIBILITY
1426 constexpr bool operator==(const variant<_Types...>& __lhs,
1427 const variant<_Types...>& __rhs) {
1428 using __variant_detail::__visitation::__variant;
1429 if (__lhs.index() != __rhs.index()) return false;
1430 if (__lhs.valueless_by_exception()) return true;
1431 return __variant::__visit_value_at(__lhs.index(), equal_to<>{}, __lhs, __rhs);
1434 template <class... _Types>
1435 inline _LIBCPP_INLINE_VISIBILITY
1436 constexpr bool operator!=(const variant<_Types...>& __lhs,
1437 const variant<_Types...>& __rhs) {
1438 using __variant_detail::__visitation::__variant;
1439 if (__lhs.index() != __rhs.index()) return true;
1440 if (__lhs.valueless_by_exception()) return false;
1441 return __variant::__visit_value_at(
1442 __lhs.index(), not_equal_to<>{}, __lhs, __rhs);
1445 template <class... _Types>
1446 inline _LIBCPP_INLINE_VISIBILITY
1447 constexpr bool operator<(const variant<_Types...>& __lhs,
1448 const variant<_Types...>& __rhs) {
1449 using __variant_detail::__visitation::__variant;
1450 if (__rhs.valueless_by_exception()) return false;
1451 if (__lhs.valueless_by_exception()) return true;
1452 if (__lhs.index() < __rhs.index()) return true;
1453 if (__lhs.index() > __rhs.index()) return false;
1454 return __variant::__visit_value_at(__lhs.index(), less<>{}, __lhs, __rhs);
1457 template <class... _Types>
1458 inline _LIBCPP_INLINE_VISIBILITY
1459 constexpr bool operator>(const variant<_Types...>& __lhs,
1460 const variant<_Types...>& __rhs) {
1461 using __variant_detail::__visitation::__variant;
1462 if (__lhs.valueless_by_exception()) return false;
1463 if (__rhs.valueless_by_exception()) return true;
1464 if (__lhs.index() > __rhs.index()) return true;
1465 if (__lhs.index() < __rhs.index()) return false;
1466 return __variant::__visit_value_at(__lhs.index(), greater<>{}, __lhs, __rhs);
1469 template <class... _Types>
1470 inline _LIBCPP_INLINE_VISIBILITY
1471 constexpr bool operator<=(const variant<_Types...>& __lhs,
1472 const variant<_Types...>& __rhs) {
1473 using __variant_detail::__visitation::__variant;
1474 if (__lhs.valueless_by_exception()) return true;
1475 if (__rhs.valueless_by_exception()) return false;
1476 if (__lhs.index() < __rhs.index()) return true;
1477 if (__lhs.index() > __rhs.index()) return false;
1478 return __variant::__visit_value_at(
1479 __lhs.index(), less_equal<>{}, __lhs, __rhs);
1482 template <class... _Types>
1483 inline _LIBCPP_INLINE_VISIBILITY
1484 constexpr bool operator>=(const variant<_Types...>& __lhs,
1485 const variant<_Types...>& __rhs) {
1486 using __variant_detail::__visitation::__variant;
1487 if (__rhs.valueless_by_exception()) return true;
1488 if (__lhs.valueless_by_exception()) return false;
1489 if (__lhs.index() > __rhs.index()) return true;
1490 if (__lhs.index() < __rhs.index()) return false;
1491 return __variant::__visit_value_at(
1492 __lhs.index(), greater_equal<>{}, __lhs, __rhs);
1495 template <class _Visitor, class... _Vs>
1496 inline _LIBCPP_INLINE_VISIBILITY
1497 constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
1498 using __variant_detail::__visitation::__variant;
1499 bool __results[] = {__vs.valueless_by_exception()...};
1500 for (bool __result : __results) {
1502 __throw_bad_variant_access();
1505 return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
1506 _VSTD::forward<_Vs>(__vs)...);
1509 struct _LIBCPP_TEMPLATE_VIS monostate {};
1511 inline _LIBCPP_INLINE_VISIBILITY
1512 constexpr bool operator<(monostate, monostate) noexcept { return false; }
1514 inline _LIBCPP_INLINE_VISIBILITY
1515 constexpr bool operator>(monostate, monostate) noexcept { return false; }
1517 inline _LIBCPP_INLINE_VISIBILITY
1518 constexpr bool operator<=(monostate, monostate) noexcept { return true; }
1520 inline _LIBCPP_INLINE_VISIBILITY
1521 constexpr bool operator>=(monostate, monostate) noexcept { return true; }
1523 inline _LIBCPP_INLINE_VISIBILITY
1524 constexpr bool operator==(monostate, monostate) noexcept { return true; }
1526 inline _LIBCPP_INLINE_VISIBILITY
1527 constexpr bool operator!=(monostate, monostate) noexcept { return false; }
1529 template <class... _Types>
1530 inline _LIBCPP_INLINE_VISIBILITY
1531 auto swap(variant<_Types...>& __lhs,
1532 variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
1533 -> decltype(__lhs.swap(__rhs)) {
1537 template <class... _Types>
1538 struct _LIBCPP_TEMPLATE_VIS hash<
1539 __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
1540 using argument_type = variant<_Types...>;
1541 using result_type = size_t;
1543 inline _LIBCPP_INLINE_VISIBILITY
1544 result_type operator()(const argument_type& __v) const {
1545 using __variant_detail::__visitation::__variant;
1547 __v.valueless_by_exception()
1548 ? 299792458 // Random value chosen by the universe upon creation
1549 : __variant::__visit_alt(
1550 [](const auto& __alt) {
1551 using __alt_type = decay_t<decltype(__alt)>;
1552 using __value_type = remove_const_t<
1553 typename __alt_type::__value_type>;
1554 return hash<__value_type>{}(__alt.__value);
1557 return __hash_combine(__res, hash<size_t>{}(__v.index()));
1562 struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
1563 using argument_type = monostate;
1564 using result_type = size_t;
1566 inline _LIBCPP_INLINE_VISIBILITY
1567 result_type operator()(const argument_type&) const _NOEXCEPT {
1568 return 66740831; // return a fundamentally attractive random value.
1572 #endif // _LIBCPP_STD_VER > 14
1574 _LIBCPP_END_NAMESPACE_STD
1576 #endif // _LIBCPP_VARIANT