Line data Source code
1 : // <optional> -*- C++ -*-
2 :
3 : // Copyright (C) 2013-2024 Free Software Foundation, Inc.
4 : // Copyright The GNU Toolchain Authors.
5 : //
6 : // This file is part of the GNU ISO C++ Library. This library is free
7 : // software; you can redistribute it and/or modify it under the
8 : // terms of the GNU General Public License as published by the
9 : // Free Software Foundation; either version 3, or (at your option)
10 : // any later version.
11 :
12 : // This library is distributed in the hope that it will be useful,
13 : // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 : // GNU General Public License for more details.
16 :
17 : // Under Section 7 of GPL version 3, you are granted additional
18 : // permissions described in the GCC Runtime Library Exception, version
19 : // 3.1, as published by the Free Software Foundation.
20 :
21 : // You should have received a copy of the GNU General Public License and
22 : // a copy of the GCC Runtime Library Exception along with this program;
23 : // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 : // <http://www.gnu.org/licenses/>.
25 :
26 : /** @file include/optional
27 : * This is a Standard C++ Library header.
28 : */
29 :
30 : #ifndef _GLIBCXX_OPTIONAL
31 : #define _GLIBCXX_OPTIONAL 1
32 :
33 : #pragma GCC system_header
34 :
35 : #define __glibcxx_want_freestanding_optional
36 : #define __glibcxx_want_optional
37 : #include <bits/version.h>
38 :
39 : #ifdef __cpp_lib_optional // C++ >= 17
40 :
41 : #include <type_traits>
42 : #include <exception>
43 : #include <new>
44 : #include <initializer_list>
45 : #include <bits/enable_special_members.h>
46 : #include <bits/exception_defines.h>
47 : #include <bits/functional_hash.h>
48 : #include <bits/stl_construct.h> // _Construct
49 : #include <bits/utility.h> // in_place_t
50 : #if __cplusplus > 201703L
51 : # include <compare>
52 : # include <bits/invoke.h> // std::__invoke
53 : #endif
54 : #if __cplusplus > 202002L
55 : # include <concepts>
56 : #endif
57 :
58 : namespace std _GLIBCXX_VISIBILITY(default)
59 : {
60 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
61 :
62 : /**
63 : * @addtogroup utilities
64 : * @{
65 : */
66 :
67 : template<typename _Tp>
68 : class optional;
69 :
70 : /// Tag type to disengage optional objects.
71 : struct nullopt_t
72 : {
73 : // Do not user-declare default constructor at all for
74 : // optional_value = {} syntax to work.
75 : // nullopt_t() = delete;
76 :
77 : // Used for constructing nullopt.
78 : enum class _Construct { _Token };
79 :
80 : // Must be constexpr for nullopt_t to be literal.
81 : explicit constexpr nullopt_t(_Construct) noexcept { }
82 : };
83 :
84 : /// Tag to disengage optional objects.
85 : inline constexpr nullopt_t nullopt { nullopt_t::_Construct::_Token };
86 :
87 : template<typename _Fn> struct _Optional_func { _Fn& _M_f; };
88 :
89 : /**
90 : * @brief Exception class thrown when a disengaged optional object is
91 : * dereferenced.
92 : * @ingroup exceptions
93 : */
94 : class bad_optional_access : public exception
95 : {
96 : public:
97 : bad_optional_access() = default;
98 : virtual ~bad_optional_access() = default;
99 :
100 : const char* what() const noexcept override
101 : { return "bad optional access"; }
102 : };
103 :
104 : // XXX Does not belong here.
105 : [[__noreturn__]] inline void
106 : __throw_bad_optional_access()
107 : { _GLIBCXX_THROW_OR_ABORT(bad_optional_access()); }
108 :
109 : // This class template manages construction/destruction of
110 : // the contained value for a std::optional.
111 : template <typename _Tp>
112 : struct _Optional_payload_base
113 : {
114 : using _Stored_type = remove_const_t<_Tp>;
115 :
116 45 : _Optional_payload_base() = default;
117 : ~_Optional_payload_base() = default;
118 :
119 : template<typename... _Args>
120 : constexpr
121 0 : _Optional_payload_base(in_place_t __tag, _Args&&... __args)
122 0 : : _M_payload(__tag, std::forward<_Args>(__args)...),
123 0 : _M_engaged(true)
124 0 : { }
125 :
126 : template<typename _Up, typename... _Args>
127 : constexpr
128 : _Optional_payload_base(std::initializer_list<_Up> __il,
129 : _Args&&... __args)
130 : : _M_payload(__il, std::forward<_Args>(__args)...),
131 : _M_engaged(true)
132 : { }
133 :
134 : // Constructor used by _Optional_base copy constructor when the
135 : // contained value is not trivially copy constructible.
136 : constexpr
137 : _Optional_payload_base(bool /* __engaged */,
138 : const _Optional_payload_base& __other)
139 : {
140 : if (__other._M_engaged)
141 : this->_M_construct(__other._M_get());
142 : }
143 :
144 : // Constructor used by _Optional_base move constructor when the
145 : // contained value is not trivially move constructible.
146 : constexpr
147 : _Optional_payload_base(bool /* __engaged */,
148 : _Optional_payload_base&& __other)
149 : {
150 : if (__other._M_engaged)
151 : this->_M_construct(std::move(__other._M_get()));
152 : }
153 :
154 : // Copy constructor is only used to when the contained value is
155 : // trivially copy constructible.
156 : _Optional_payload_base(const _Optional_payload_base&) = default;
157 :
158 : // Move constructor is only used to when the contained value is
159 : // trivially copy constructible.
160 : _Optional_payload_base(_Optional_payload_base&&) = default;
161 :
162 : _Optional_payload_base&
163 : operator=(const _Optional_payload_base&) = default;
164 :
165 : _Optional_payload_base&
166 : operator=(_Optional_payload_base&&) = default;
167 :
168 : // used to perform non-trivial copy assignment.
169 : constexpr void
170 : _M_copy_assign(const _Optional_payload_base& __other)
171 : {
172 : if (this->_M_engaged && __other._M_engaged)
173 : this->_M_get() = __other._M_get();
174 : else
175 : {
176 : if (__other._M_engaged)
177 : this->_M_construct(__other._M_get());
178 : else
179 : this->_M_reset();
180 : }
181 : }
182 :
183 : // used to perform non-trivial move assignment.
184 : constexpr void
185 : _M_move_assign(_Optional_payload_base&& __other)
186 : noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
187 : is_nothrow_move_assignable<_Tp>>)
188 : {
189 : if (this->_M_engaged && __other._M_engaged)
190 : this->_M_get() = std::move(__other._M_get());
191 : else
192 : {
193 : if (__other._M_engaged)
194 : this->_M_construct(std::move(__other._M_get()));
195 : else
196 : this->_M_reset();
197 : }
198 : }
199 :
200 : struct _Empty_byte { };
201 :
202 : template<typename _Up, bool = is_trivially_destructible_v<_Up>>
203 : union _Storage
204 : {
205 45 : constexpr _Storage() noexcept : _M_empty() { }
206 :
207 : template<typename... _Args>
208 : constexpr
209 0 : _Storage(in_place_t, _Args&&... __args)
210 0 : : _M_value(std::forward<_Args>(__args)...)
211 0 : { }
212 :
213 : template<typename _Vp, typename... _Args>
214 : constexpr
215 : _Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
216 : : _M_value(__il, std::forward<_Args>(__args)...)
217 : { }
218 :
219 : #if __cplusplus >= 202002L
220 : template<typename _Fn, typename _Arg>
221 : constexpr
222 : _Storage(_Optional_func<_Fn> __f, _Arg&& __arg)
223 : : _M_value(std::__invoke(std::forward<_Fn>(__f._M_f),
224 : std::forward<_Arg>(__arg)))
225 : { }
226 : #endif
227 :
228 : _Empty_byte _M_empty;
229 : _Up _M_value;
230 : };
231 :
232 : template<typename _Up>
233 : union _Storage<_Up, false>
234 : {
235 : constexpr _Storage() noexcept : _M_empty() { }
236 :
237 : template<typename... _Args>
238 : constexpr
239 : _Storage(in_place_t, _Args&&... __args)
240 : : _M_value(std::forward<_Args>(__args)...)
241 : { }
242 :
243 : template<typename _Vp, typename... _Args>
244 : constexpr
245 : _Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
246 : : _M_value(__il, std::forward<_Args>(__args)...)
247 : { }
248 :
249 : #if __cplusplus >= 202002L
250 : template<typename _Fn, typename _Arg>
251 : constexpr
252 : _Storage(_Optional_func<_Fn> __f, _Arg&& __arg)
253 : : _M_value(std::__invoke(std::forward<_Fn>(__f._M_f),
254 : std::forward<_Arg>(__arg)))
255 : { }
256 : #endif
257 :
258 : // User-provided destructor is needed when _Up has non-trivial dtor.
259 : _GLIBCXX20_CONSTEXPR ~_Storage() { }
260 :
261 : _Empty_byte _M_empty;
262 : _Up _M_value;
263 : };
264 :
265 : _Storage<_Stored_type> _M_payload;
266 :
267 : bool _M_engaged = false;
268 :
269 : template<typename... _Args>
270 : constexpr void
271 : _M_construct(_Args&&... __args)
272 : noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
273 : {
274 : std::_Construct(std::__addressof(this->_M_payload._M_value),
275 : std::forward<_Args>(__args)...);
276 : this->_M_engaged = true;
277 : }
278 :
279 : constexpr void
280 : _M_destroy() noexcept
281 : {
282 : _M_engaged = false;
283 : _M_payload._M_value.~_Stored_type();
284 : }
285 :
286 : #if __cplusplus >= 202002L
287 : template<typename _Fn, typename _Up>
288 : constexpr void
289 : _M_apply(_Optional_func<_Fn> __f, _Up&& __x)
290 : {
291 : std::construct_at(std::__addressof(this->_M_payload),
292 : __f, std::forward<_Up>(__x));
293 : _M_engaged = true;
294 : }
295 : #endif
296 :
297 : // The _M_get() operations have _M_engaged as a precondition.
298 : // They exist to access the contained value with the appropriate
299 : // const-qualification, because _M_payload has had the const removed.
300 :
301 : constexpr _Tp&
302 : _M_get() noexcept
303 : { return this->_M_payload._M_value; }
304 :
305 : constexpr const _Tp&
306 : _M_get() const noexcept
307 : { return this->_M_payload._M_value; }
308 :
309 : // _M_reset is a 'safe' operation with no precondition.
310 : constexpr void
311 : _M_reset() noexcept
312 : {
313 : if (this->_M_engaged)
314 : _M_destroy();
315 : else // This seems redundant but improves codegen, see PR 112480.
316 : this->_M_engaged = false;
317 : }
318 : };
319 :
320 : // Class template that manages the payload for optionals.
321 : template <typename _Tp,
322 : bool /*_HasTrivialDestructor*/ =
323 : is_trivially_destructible_v<_Tp>,
324 : bool /*_HasTrivialCopy */ =
325 : is_trivially_copy_assignable_v<_Tp>
326 : && is_trivially_copy_constructible_v<_Tp>,
327 : bool /*_HasTrivialMove */ =
328 : is_trivially_move_assignable_v<_Tp>
329 : && is_trivially_move_constructible_v<_Tp>>
330 : struct _Optional_payload;
331 :
332 : // Payload for potentially-constexpr optionals (trivial copy/move/destroy).
333 : template <typename _Tp>
334 : struct _Optional_payload<_Tp, true, true, true>
335 : : _Optional_payload_base<_Tp>
336 : {
337 : using _Optional_payload_base<_Tp>::_Optional_payload_base;
338 :
339 45 : _Optional_payload() = default;
340 : };
341 :
342 : // Payload for optionals with non-trivial copy construction/assignment.
343 : template <typename _Tp>
344 : struct _Optional_payload<_Tp, true, false, true>
345 : : _Optional_payload_base<_Tp>
346 : {
347 : using _Optional_payload_base<_Tp>::_Optional_payload_base;
348 :
349 : _Optional_payload() = default;
350 : ~_Optional_payload() = default;
351 : _Optional_payload(const _Optional_payload&) = default;
352 : _Optional_payload(_Optional_payload&&) = default;
353 : _Optional_payload& operator=(_Optional_payload&&) = default;
354 :
355 : // Non-trivial copy assignment.
356 : constexpr
357 : _Optional_payload&
358 : operator=(const _Optional_payload& __other)
359 : {
360 : this->_M_copy_assign(__other);
361 : return *this;
362 : }
363 : };
364 :
365 : // Payload for optionals with non-trivial move construction/assignment.
366 : template <typename _Tp>
367 : struct _Optional_payload<_Tp, true, true, false>
368 : : _Optional_payload_base<_Tp>
369 : {
370 : using _Optional_payload_base<_Tp>::_Optional_payload_base;
371 :
372 : _Optional_payload() = default;
373 : ~_Optional_payload() = default;
374 : _Optional_payload(const _Optional_payload&) = default;
375 : _Optional_payload(_Optional_payload&&) = default;
376 : _Optional_payload& operator=(const _Optional_payload&) = default;
377 :
378 : // Non-trivial move assignment.
379 : constexpr
380 : _Optional_payload&
381 : operator=(_Optional_payload&& __other)
382 : noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
383 : is_nothrow_move_assignable<_Tp>>)
384 : {
385 : this->_M_move_assign(std::move(__other));
386 : return *this;
387 : }
388 : };
389 :
390 : // Payload for optionals with non-trivial copy and move assignment.
391 : template <typename _Tp>
392 : struct _Optional_payload<_Tp, true, false, false>
393 : : _Optional_payload_base<_Tp>
394 : {
395 : using _Optional_payload_base<_Tp>::_Optional_payload_base;
396 :
397 : _Optional_payload() = default;
398 : ~_Optional_payload() = default;
399 : _Optional_payload(const _Optional_payload&) = default;
400 : _Optional_payload(_Optional_payload&&) = default;
401 :
402 : // Non-trivial copy assignment.
403 : constexpr
404 : _Optional_payload&
405 : operator=(const _Optional_payload& __other)
406 : {
407 : this->_M_copy_assign(__other);
408 : return *this;
409 : }
410 :
411 : // Non-trivial move assignment.
412 : constexpr
413 : _Optional_payload&
414 : operator=(_Optional_payload&& __other)
415 : noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
416 : is_nothrow_move_assignable<_Tp>>)
417 : {
418 : this->_M_move_assign(std::move(__other));
419 : return *this;
420 : }
421 : };
422 :
423 : // Payload for optionals with non-trivial destructors.
424 : template <typename _Tp, bool _Copy, bool _Move>
425 : struct _Optional_payload<_Tp, false, _Copy, _Move>
426 : : _Optional_payload<_Tp, true, false, false>
427 : {
428 : // Base class implements all the constructors and assignment operators:
429 : using _Optional_payload<_Tp, true, false, false>::_Optional_payload;
430 : _Optional_payload() = default;
431 : _Optional_payload(const _Optional_payload&) = default;
432 : _Optional_payload(_Optional_payload&&) = default;
433 : _Optional_payload& operator=(const _Optional_payload&) = default;
434 : _Optional_payload& operator=(_Optional_payload&&) = default;
435 :
436 : // Destructor needs to destroy the contained value:
437 : _GLIBCXX20_CONSTEXPR ~_Optional_payload() { this->_M_reset(); }
438 : };
439 :
440 : // Common base class for _Optional_base<T> to avoid repeating these
441 : // member functions in each specialization.
442 : template<typename _Tp, typename _Dp>
443 : class _Optional_base_impl
444 : {
445 : protected:
446 : using _Stored_type = remove_const_t<_Tp>;
447 :
448 : // The _M_construct operation has !_M_engaged as a precondition
449 : // while _M_destruct has _M_engaged as a precondition.
450 : template<typename... _Args>
451 : constexpr void
452 : _M_construct(_Args&&... __args)
453 : noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
454 : {
455 : static_cast<_Dp*>(this)->_M_payload._M_construct(
456 : std::forward<_Args>(__args)...);
457 : }
458 :
459 : constexpr void
460 : _M_destruct() noexcept
461 : { static_cast<_Dp*>(this)->_M_payload._M_destroy(); }
462 :
463 : // _M_reset is a 'safe' operation with no precondition.
464 : constexpr void
465 : _M_reset() noexcept
466 : { static_cast<_Dp*>(this)->_M_payload._M_reset(); }
467 :
468 : constexpr bool _M_is_engaged() const noexcept
469 : { return static_cast<const _Dp*>(this)->_M_payload._M_engaged; }
470 :
471 : // The _M_get operations have _M_engaged as a precondition.
472 : constexpr _Tp&
473 : _M_get() noexcept
474 : {
475 : __glibcxx_assert(this->_M_is_engaged());
476 : return static_cast<_Dp*>(this)->_M_payload._M_get();
477 : }
478 :
479 : constexpr const _Tp&
480 : _M_get() const noexcept
481 : {
482 : __glibcxx_assert(this->_M_is_engaged());
483 : return static_cast<const _Dp*>(this)->_M_payload._M_get();
484 : }
485 : };
486 :
487 : /**
488 : * @brief Class template that provides copy/move constructors of optional.
489 : *
490 : * Such a separate base class template is necessary in order to
491 : * conditionally make copy/move constructors trivial.
492 : *
493 : * When the contained value is trivially copy/move constructible,
494 : * the copy/move constructors of _Optional_base will invoke the
495 : * trivial copy/move constructor of _Optional_payload. Otherwise,
496 : * they will invoke _Optional_payload(bool, const _Optional_payload&)
497 : * or _Optional_payload(bool, _Optional_payload&&) to initialize
498 : * the contained value, if copying/moving an engaged optional.
499 : *
500 : * Whether the other special members are trivial is determined by the
501 : * _Optional_payload<_Tp> specialization used for the _M_payload member.
502 : *
503 : * @see optional, _Enable_special_members
504 : */
505 : template<typename _Tp,
506 : bool = is_trivially_copy_constructible_v<_Tp>,
507 : bool = is_trivially_move_constructible_v<_Tp>>
508 : struct _Optional_base
509 : : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
510 : {
511 : // Constructors for disengaged optionals.
512 : constexpr _Optional_base() = default;
513 :
514 : // Constructors for engaged optionals.
515 : template<typename... _Args,
516 : enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
517 : constexpr explicit
518 : _Optional_base(in_place_t, _Args&&... __args)
519 : : _M_payload(in_place, std::forward<_Args>(__args)...)
520 : { }
521 :
522 : template<typename _Up, typename... _Args,
523 : enable_if_t<is_constructible_v<_Tp,
524 : initializer_list<_Up>&,
525 : _Args...>, bool> = false>
526 : constexpr explicit
527 : _Optional_base(in_place_t,
528 : initializer_list<_Up> __il,
529 : _Args&&... __args)
530 : : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
531 : { }
532 :
533 : // Copy and move constructors.
534 : constexpr
535 : _Optional_base(const _Optional_base& __other)
536 : : _M_payload(__other._M_payload._M_engaged, __other._M_payload)
537 : { }
538 :
539 : constexpr
540 : _Optional_base(_Optional_base&& __other)
541 : noexcept(is_nothrow_move_constructible_v<_Tp>)
542 : : _M_payload(__other._M_payload._M_engaged,
543 : std::move(__other._M_payload))
544 : { }
545 :
546 : // Assignment operators.
547 : _Optional_base& operator=(const _Optional_base&) = default;
548 : _Optional_base& operator=(_Optional_base&&) = default;
549 :
550 : _Optional_payload<_Tp> _M_payload;
551 : };
552 :
553 : template<typename _Tp>
554 : struct _Optional_base<_Tp, false, true>
555 : : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
556 : {
557 : // Constructors for disengaged optionals.
558 : constexpr _Optional_base() = default;
559 :
560 : // Constructors for engaged optionals.
561 : template<typename... _Args,
562 : enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
563 : constexpr explicit
564 : _Optional_base(in_place_t, _Args&&... __args)
565 : : _M_payload(in_place, std::forward<_Args>(__args)...)
566 : { }
567 :
568 : template<typename _Up, typename... _Args,
569 : enable_if_t<is_constructible_v<_Tp,
570 : initializer_list<_Up>&,
571 : _Args...>, bool> = false>
572 : constexpr explicit
573 : _Optional_base(in_place_t,
574 : initializer_list<_Up> __il,
575 : _Args... __args)
576 : : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
577 : { }
578 :
579 : // Copy and move constructors.
580 : constexpr _Optional_base(const _Optional_base& __other)
581 : : _M_payload(__other._M_payload._M_engaged, __other._M_payload)
582 : { }
583 :
584 : constexpr _Optional_base(_Optional_base&& __other) = default;
585 :
586 : // Assignment operators.
587 : _Optional_base& operator=(const _Optional_base&) = default;
588 : _Optional_base& operator=(_Optional_base&&) = default;
589 :
590 : _Optional_payload<_Tp> _M_payload;
591 : };
592 :
593 : template<typename _Tp>
594 : struct _Optional_base<_Tp, true, false>
595 : : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
596 : {
597 : // Constructors for disengaged optionals.
598 : constexpr _Optional_base() = default;
599 :
600 : // Constructors for engaged optionals.
601 : template<typename... _Args,
602 : enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
603 : constexpr explicit
604 : _Optional_base(in_place_t, _Args&&... __args)
605 : : _M_payload(in_place, std::forward<_Args>(__args)...)
606 : { }
607 :
608 : template<typename _Up, typename... _Args,
609 : enable_if_t<is_constructible_v<_Tp,
610 : initializer_list<_Up>&,
611 : _Args...>, bool> = false>
612 : constexpr explicit
613 : _Optional_base(in_place_t,
614 : initializer_list<_Up> __il,
615 : _Args&&... __args)
616 : : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
617 : { }
618 :
619 : // Copy and move constructors.
620 : constexpr _Optional_base(const _Optional_base& __other) = default;
621 :
622 : constexpr
623 : _Optional_base(_Optional_base&& __other)
624 : noexcept(is_nothrow_move_constructible_v<_Tp>)
625 : : _M_payload(__other._M_payload._M_engaged,
626 : std::move(__other._M_payload))
627 : { }
628 :
629 : // Assignment operators.
630 : _Optional_base& operator=(const _Optional_base&) = default;
631 : _Optional_base& operator=(_Optional_base&&) = default;
632 :
633 : _Optional_payload<_Tp> _M_payload;
634 : };
635 :
636 : template<typename _Tp>
637 : struct _Optional_base<_Tp, true, true>
638 : : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
639 : {
640 : // Constructors for disengaged optionals.
641 45 : constexpr _Optional_base() = default;
642 :
643 : // Constructors for engaged optionals.
644 : template<typename... _Args,
645 : enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
646 : constexpr explicit
647 0 : _Optional_base(in_place_t, _Args&&... __args)
648 0 : : _M_payload(in_place, std::forward<_Args>(__args)...)
649 0 : { }
650 :
651 : template<typename _Up, typename... _Args,
652 : enable_if_t<is_constructible_v<_Tp,
653 : initializer_list<_Up>&,
654 : _Args...>, bool> = false>
655 : constexpr explicit
656 : _Optional_base(in_place_t,
657 : initializer_list<_Up> __il,
658 : _Args&&... __args)
659 : : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
660 : { }
661 :
662 : // Copy and move constructors.
663 : constexpr _Optional_base(const _Optional_base& __other) = default;
664 : constexpr _Optional_base(_Optional_base&& __other) = default;
665 :
666 : // Assignment operators.
667 : _Optional_base& operator=(const _Optional_base&) = default;
668 : _Optional_base& operator=(_Optional_base&&) = default;
669 :
670 : _Optional_payload<_Tp> _M_payload;
671 : };
672 :
673 : template<typename _Tp>
674 : class optional;
675 :
676 : template<typename _Tp>
677 : inline constexpr bool __is_optional_v = false;
678 : template<typename _Tp>
679 : inline constexpr bool __is_optional_v<optional<_Tp>> = true;
680 :
681 : template<typename _Tp, typename _Up>
682 : using __converts_from_optional =
683 : __or_<is_constructible<_Tp, const optional<_Up>&>,
684 : is_constructible<_Tp, optional<_Up>&>,
685 : is_constructible<_Tp, const optional<_Up>&&>,
686 : is_constructible<_Tp, optional<_Up>&&>,
687 : is_convertible<const optional<_Up>&, _Tp>,
688 : is_convertible<optional<_Up>&, _Tp>,
689 : is_convertible<const optional<_Up>&&, _Tp>,
690 : is_convertible<optional<_Up>&&, _Tp>>;
691 :
692 : template<typename _Tp, typename _Up>
693 : using __assigns_from_optional =
694 : __or_<is_assignable<_Tp&, const optional<_Up>&>,
695 : is_assignable<_Tp&, optional<_Up>&>,
696 : is_assignable<_Tp&, const optional<_Up>&&>,
697 : is_assignable<_Tp&, optional<_Up>&&>>;
698 :
699 : /**
700 : * @brief Class template for optional values.
701 : */
702 : template<typename _Tp>
703 : class optional
704 : : private _Optional_base<_Tp>,
705 : private _Enable_copy_move<
706 : // Copy constructor.
707 : is_copy_constructible_v<_Tp>,
708 : // Copy assignment.
709 : __and_v<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>,
710 : // Move constructor.
711 : is_move_constructible_v<_Tp>,
712 : // Move assignment.
713 : __and_v<is_move_constructible<_Tp>, is_move_assignable<_Tp>>,
714 : // Unique tag type.
715 : optional<_Tp>>
716 : {
717 : static_assert(!is_same_v<remove_cv_t<_Tp>, nullopt_t>);
718 : static_assert(!is_same_v<remove_cv_t<_Tp>, in_place_t>);
719 : static_assert(is_object_v<_Tp> && !is_array_v<_Tp>);
720 :
721 : private:
722 : using _Base = _Optional_base<_Tp>;
723 :
724 : // SFINAE helpers
725 : template<typename _Up>
726 : using __not_self = __not_<is_same<optional, __remove_cvref_t<_Up>>>;
727 : template<typename _Up>
728 : using __not_tag = __not_<is_same<in_place_t, __remove_cvref_t<_Up>>>;
729 : template<typename... _Cond>
730 : using _Requires = enable_if_t<__and_v<_Cond...>, bool>;
731 :
732 : public:
733 : using value_type = _Tp;
734 :
735 : constexpr optional() noexcept { }
736 :
737 45 : constexpr optional(nullopt_t) noexcept { }
738 :
739 : // Converting constructors for engaged optionals.
740 : template<typename _Up = _Tp,
741 : _Requires<__not_self<_Up>, __not_tag<_Up>,
742 : is_constructible<_Tp, _Up>,
743 : is_convertible<_Up, _Tp>> = true>
744 : constexpr
745 : optional(_Up&& __t)
746 : noexcept(is_nothrow_constructible_v<_Tp, _Up>)
747 : : _Base(std::in_place, std::forward<_Up>(__t)) { }
748 :
749 : template<typename _Up = _Tp,
750 : _Requires<__not_self<_Up>, __not_tag<_Up>,
751 : is_constructible<_Tp, _Up>,
752 : __not_<is_convertible<_Up, _Tp>>> = false>
753 : explicit constexpr
754 : optional(_Up&& __t)
755 : noexcept(is_nothrow_constructible_v<_Tp, _Up>)
756 : : _Base(std::in_place, std::forward<_Up>(__t)) { }
757 :
758 : template<typename _Up,
759 : _Requires<__not_<is_same<_Tp, _Up>>,
760 : is_constructible<_Tp, const _Up&>,
761 : is_convertible<const _Up&, _Tp>,
762 : __not_<__converts_from_optional<_Tp, _Up>>> = true>
763 : constexpr
764 : optional(const optional<_Up>& __t)
765 : noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
766 : {
767 : if (__t)
768 : emplace(*__t);
769 : }
770 :
771 : template<typename _Up,
772 : _Requires<__not_<is_same<_Tp, _Up>>,
773 : is_constructible<_Tp, const _Up&>,
774 : __not_<is_convertible<const _Up&, _Tp>>,
775 : __not_<__converts_from_optional<_Tp, _Up>>> = false>
776 : explicit constexpr
777 : optional(const optional<_Up>& __t)
778 : noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
779 : {
780 : if (__t)
781 : emplace(*__t);
782 : }
783 :
784 : template<typename _Up,
785 : _Requires<__not_<is_same<_Tp, _Up>>,
786 : is_constructible<_Tp, _Up>,
787 : is_convertible<_Up, _Tp>,
788 : __not_<__converts_from_optional<_Tp, _Up>>> = true>
789 : constexpr
790 : optional(optional<_Up>&& __t)
791 : noexcept(is_nothrow_constructible_v<_Tp, _Up>)
792 : {
793 : if (__t)
794 : emplace(std::move(*__t));
795 : }
796 :
797 : template<typename _Up,
798 : _Requires<__not_<is_same<_Tp, _Up>>,
799 : is_constructible<_Tp, _Up>,
800 : __not_<is_convertible<_Up, _Tp>>,
801 : __not_<__converts_from_optional<_Tp, _Up>>> = false>
802 : explicit constexpr
803 : optional(optional<_Up>&& __t)
804 : noexcept(is_nothrow_constructible_v<_Tp, _Up>)
805 : {
806 : if (__t)
807 : emplace(std::move(*__t));
808 : }
809 :
810 : template<typename... _Args,
811 : _Requires<is_constructible<_Tp, _Args...>> = false>
812 : explicit constexpr
813 0 : optional(in_place_t, _Args&&... __args)
814 : noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
815 0 : : _Base(std::in_place, std::forward<_Args>(__args)...) { }
816 :
817 : template<typename _Up, typename... _Args,
818 : _Requires<is_constructible<_Tp,
819 : initializer_list<_Up>&,
820 : _Args...>> = false>
821 : explicit constexpr
822 : optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
823 : noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
824 : _Args...>)
825 : : _Base(std::in_place, __il, std::forward<_Args>(__args)...) { }
826 :
827 :
828 : // Assignment operators.
829 : _GLIBCXX20_CONSTEXPR optional&
830 : operator=(nullopt_t) noexcept
831 : {
832 : this->_M_reset();
833 : return *this;
834 : }
835 :
836 : template<typename _Up = _Tp>
837 : _GLIBCXX20_CONSTEXPR
838 : enable_if_t<__and_v<__not_self<_Up>,
839 : __not_<__and_<is_scalar<_Tp>,
840 : is_same<_Tp, decay_t<_Up>>>>,
841 : is_constructible<_Tp, _Up>,
842 : is_assignable<_Tp&, _Up>>,
843 : optional&>
844 : operator=(_Up&& __u)
845 : noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
846 : is_nothrow_assignable<_Tp&, _Up>>)
847 : {
848 : if (this->_M_is_engaged())
849 : this->_M_get() = std::forward<_Up>(__u);
850 : else
851 : this->_M_construct(std::forward<_Up>(__u));
852 :
853 : return *this;
854 : }
855 :
856 : template<typename _Up>
857 : _GLIBCXX20_CONSTEXPR
858 : enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
859 : is_constructible<_Tp, const _Up&>,
860 : is_assignable<_Tp&, const _Up&>,
861 : __not_<__converts_from_optional<_Tp, _Up>>,
862 : __not_<__assigns_from_optional<_Tp, _Up>>>,
863 : optional&>
864 : operator=(const optional<_Up>& __u)
865 : noexcept(__and_v<is_nothrow_constructible<_Tp, const _Up&>,
866 : is_nothrow_assignable<_Tp&, const _Up&>>)
867 : {
868 : if (__u)
869 : {
870 : if (this->_M_is_engaged())
871 : this->_M_get() = *__u;
872 : else
873 : this->_M_construct(*__u);
874 : }
875 : else
876 : {
877 : this->_M_reset();
878 : }
879 : return *this;
880 : }
881 :
882 : template<typename _Up>
883 : _GLIBCXX20_CONSTEXPR
884 : enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
885 : is_constructible<_Tp, _Up>,
886 : is_assignable<_Tp&, _Up>,
887 : __not_<__converts_from_optional<_Tp, _Up>>,
888 : __not_<__assigns_from_optional<_Tp, _Up>>>,
889 : optional&>
890 : operator=(optional<_Up>&& __u)
891 : noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
892 : is_nothrow_assignable<_Tp&, _Up>>)
893 : {
894 : if (__u)
895 : {
896 : if (this->_M_is_engaged())
897 : this->_M_get() = std::move(*__u);
898 : else
899 : this->_M_construct(std::move(*__u));
900 : }
901 : else
902 : {
903 : this->_M_reset();
904 : }
905 :
906 : return *this;
907 : }
908 :
909 : template<typename... _Args>
910 : _GLIBCXX20_CONSTEXPR
911 : enable_if_t<is_constructible_v<_Tp, _Args...>, _Tp&>
912 : emplace(_Args&&... __args)
913 : noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
914 : {
915 : this->_M_reset();
916 : this->_M_construct(std::forward<_Args>(__args)...);
917 : return this->_M_get();
918 : }
919 :
920 : template<typename _Up, typename... _Args>
921 : _GLIBCXX20_CONSTEXPR
922 : enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
923 : _Tp&>
924 : emplace(initializer_list<_Up> __il, _Args&&... __args)
925 : noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
926 : _Args...>)
927 : {
928 : this->_M_reset();
929 : this->_M_construct(__il, std::forward<_Args>(__args)...);
930 : return this->_M_get();
931 : }
932 :
933 : // Destructor is implicit, implemented in _Optional_base.
934 :
935 : // Swap.
936 : _GLIBCXX20_CONSTEXPR void
937 : swap(optional& __other)
938 : noexcept(is_nothrow_move_constructible_v<_Tp>
939 : && is_nothrow_swappable_v<_Tp>)
940 : {
941 : using std::swap;
942 :
943 : if (this->_M_is_engaged() && __other._M_is_engaged())
944 : swap(this->_M_get(), __other._M_get());
945 : else if (this->_M_is_engaged())
946 : {
947 : __other._M_construct(std::move(this->_M_get()));
948 : this->_M_destruct();
949 : }
950 : else if (__other._M_is_engaged())
951 : {
952 : this->_M_construct(std::move(__other._M_get()));
953 : __other._M_destruct();
954 : }
955 : }
956 :
957 : // Observers.
958 : constexpr const _Tp*
959 : operator->() const noexcept
960 : { return std::__addressof(this->_M_get()); }
961 :
962 : constexpr _Tp*
963 : operator->() noexcept
964 : { return std::__addressof(this->_M_get()); }
965 :
966 : constexpr const _Tp&
967 : operator*() const& noexcept
968 : { return this->_M_get(); }
969 :
970 : constexpr _Tp&
971 : operator*()& noexcept
972 : { return this->_M_get(); }
973 :
974 : constexpr _Tp&&
975 : operator*()&& noexcept
976 : { return std::move(this->_M_get()); }
977 :
978 : constexpr const _Tp&&
979 : operator*() const&& noexcept
980 : { return std::move(this->_M_get()); }
981 :
982 : constexpr explicit operator bool() const noexcept
983 : { return this->_M_is_engaged(); }
984 :
985 : constexpr bool has_value() const noexcept
986 : { return this->_M_is_engaged(); }
987 :
988 : constexpr const _Tp&
989 : value() const&
990 : {
991 : if (this->_M_is_engaged())
992 : return this->_M_get();
993 : __throw_bad_optional_access();
994 : }
995 :
996 : constexpr _Tp&
997 : value()&
998 : {
999 : if (this->_M_is_engaged())
1000 : return this->_M_get();
1001 : __throw_bad_optional_access();
1002 : }
1003 :
1004 : constexpr _Tp&&
1005 : value()&&
1006 : {
1007 : if (this->_M_is_engaged())
1008 : return std::move(this->_M_get());
1009 : __throw_bad_optional_access();
1010 : }
1011 :
1012 : constexpr const _Tp&&
1013 : value() const&&
1014 : {
1015 : if (this->_M_is_engaged())
1016 : return std::move(this->_M_get());
1017 : __throw_bad_optional_access();
1018 : }
1019 :
1020 : template<typename _Up>
1021 : constexpr _Tp
1022 : value_or(_Up&& __u) const&
1023 : {
1024 : static_assert(is_copy_constructible_v<_Tp>);
1025 : static_assert(is_convertible_v<_Up&&, _Tp>);
1026 :
1027 : if (this->_M_is_engaged())
1028 : return this->_M_get();
1029 : else
1030 : return static_cast<_Tp>(std::forward<_Up>(__u));
1031 : }
1032 :
1033 : template<typename _Up>
1034 : constexpr _Tp
1035 : value_or(_Up&& __u) &&
1036 : {
1037 : static_assert(is_move_constructible_v<_Tp>);
1038 : static_assert(is_convertible_v<_Up&&, _Tp>);
1039 :
1040 : if (this->_M_is_engaged())
1041 : return std::move(this->_M_get());
1042 : else
1043 : return static_cast<_Tp>(std::forward<_Up>(__u));
1044 : }
1045 :
1046 : #if __cpp_lib_optional >= 202110L
1047 : // [optional.monadic]
1048 :
1049 : template<typename _Fn>
1050 : constexpr auto
1051 : and_then(_Fn&& __f) &
1052 : {
1053 : using _Up = remove_cvref_t<invoke_result_t<_Fn, _Tp&>>;
1054 : static_assert(__is_optional_v<remove_cvref_t<_Up>>,
1055 : "the function passed to std::optional<T>::and_then "
1056 : "must return a std::optional");
1057 : if (has_value())
1058 : return std::__invoke(std::forward<_Fn>(__f), **this);
1059 : else
1060 : return _Up();
1061 : }
1062 :
1063 : template<typename _Fn>
1064 : constexpr auto
1065 : and_then(_Fn&& __f) const &
1066 : {
1067 : using _Up = remove_cvref_t<invoke_result_t<_Fn, const _Tp&>>;
1068 : static_assert(__is_optional_v<_Up>,
1069 : "the function passed to std::optional<T>::and_then "
1070 : "must return a std::optional");
1071 : if (has_value())
1072 : return std::__invoke(std::forward<_Fn>(__f), **this);
1073 : else
1074 : return _Up();
1075 : }
1076 :
1077 : template<typename _Fn>
1078 : constexpr auto
1079 : and_then(_Fn&& __f) &&
1080 : {
1081 : using _Up = remove_cvref_t<invoke_result_t<_Fn, _Tp>>;
1082 : static_assert(__is_optional_v<remove_cvref_t<_Up>>,
1083 : "the function passed to std::optional<T>::and_then "
1084 : "must return a std::optional");
1085 : if (has_value())
1086 : return std::__invoke(std::forward<_Fn>(__f), std::move(**this));
1087 : else
1088 : return _Up();
1089 : }
1090 :
1091 : template<typename _Fn>
1092 : constexpr auto
1093 : and_then(_Fn&& __f) const &&
1094 : {
1095 : using _Up = remove_cvref_t<invoke_result_t<_Fn, const _Tp>>;
1096 : static_assert(__is_optional_v<remove_cvref_t<_Up>>,
1097 : "the function passed to std::optional<T>::and_then "
1098 : "must return a std::optional");
1099 : if (has_value())
1100 : return std::__invoke(std::forward<_Fn>(__f), std::move(**this));
1101 : else
1102 : return _Up();
1103 : }
1104 :
1105 : template<typename _Fn>
1106 : constexpr auto
1107 : transform(_Fn&& __f) &
1108 : {
1109 : using _Up = remove_cv_t<invoke_result_t<_Fn, _Tp&>>;
1110 : if (has_value())
1111 : return optional<_Up>(_Optional_func<_Fn>{__f}, **this);
1112 : else
1113 : return optional<_Up>();
1114 : }
1115 :
1116 : template<typename _Fn>
1117 : constexpr auto
1118 : transform(_Fn&& __f) const &
1119 : {
1120 : using _Up = remove_cv_t<invoke_result_t<_Fn, const _Tp&>>;
1121 : if (has_value())
1122 : return optional<_Up>(_Optional_func<_Fn>{__f}, **this);
1123 : else
1124 : return optional<_Up>();
1125 : }
1126 :
1127 : template<typename _Fn>
1128 : constexpr auto
1129 : transform(_Fn&& __f) &&
1130 : {
1131 : using _Up = remove_cv_t<invoke_result_t<_Fn, _Tp>>;
1132 : if (has_value())
1133 : return optional<_Up>(_Optional_func<_Fn>{__f}, std::move(**this));
1134 : else
1135 : return optional<_Up>();
1136 : }
1137 :
1138 : template<typename _Fn>
1139 : constexpr auto
1140 : transform(_Fn&& __f) const &&
1141 : {
1142 : using _Up = remove_cv_t<invoke_result_t<_Fn, const _Tp>>;
1143 : if (has_value())
1144 : return optional<_Up>(_Optional_func<_Fn>{__f}, std::move(**this));
1145 : else
1146 : return optional<_Up>();
1147 : }
1148 :
1149 : template<typename _Fn> requires invocable<_Fn> && copy_constructible<_Tp>
1150 : constexpr optional
1151 : or_else(_Fn&& __f) const&
1152 : {
1153 : using _Up = invoke_result_t<_Fn>;
1154 : static_assert(is_same_v<remove_cvref_t<_Up>, optional>,
1155 : "the function passed to std::optional<T>::or_else "
1156 : "must return a std::optional<T>");
1157 :
1158 : if (has_value())
1159 : return *this;
1160 : else
1161 : return std::forward<_Fn>(__f)();
1162 : }
1163 :
1164 : template<typename _Fn> requires invocable<_Fn> && move_constructible<_Tp>
1165 : constexpr optional
1166 : or_else(_Fn&& __f) &&
1167 : {
1168 : using _Up = invoke_result_t<_Fn>;
1169 : static_assert(is_same_v<remove_cvref_t<_Up>, optional>,
1170 : "the function passed to std::optional<T>::or_else "
1171 : "must return a std::optional<T>");
1172 :
1173 : if (has_value())
1174 : return std::move(*this);
1175 : else
1176 : return std::forward<_Fn>(__f)();
1177 : }
1178 : #endif
1179 :
1180 : _GLIBCXX20_CONSTEXPR void reset() noexcept { this->_M_reset(); }
1181 :
1182 : private:
1183 : #if __cplusplus >= 202002L
1184 : template<typename _Up> friend class optional;
1185 :
1186 : template<typename _Fn, typename _Value>
1187 : explicit constexpr
1188 : optional(_Optional_func<_Fn> __f, _Value&& __v)
1189 : {
1190 : this->_M_payload._M_apply(__f, std::forward<_Value>(__v));
1191 : }
1192 : #endif
1193 : };
1194 :
1195 : template<typename _Tp>
1196 : using __optional_relop_t =
1197 : enable_if_t<is_convertible<_Tp, bool>::value, bool>;
1198 :
1199 : template<typename _Tp, typename _Up>
1200 : using __optional_eq_t = __optional_relop_t<
1201 : decltype(std::declval<const _Tp&>() == std::declval<const _Up&>())
1202 : >;
1203 :
1204 : template<typename _Tp, typename _Up>
1205 : using __optional_ne_t = __optional_relop_t<
1206 : decltype(std::declval<const _Tp&>() != std::declval<const _Up&>())
1207 : >;
1208 :
1209 : template<typename _Tp, typename _Up>
1210 : using __optional_lt_t = __optional_relop_t<
1211 : decltype(std::declval<const _Tp&>() < std::declval<const _Up&>())
1212 : >;
1213 :
1214 : template<typename _Tp, typename _Up>
1215 : using __optional_gt_t = __optional_relop_t<
1216 : decltype(std::declval<const _Tp&>() > std::declval<const _Up&>())
1217 : >;
1218 :
1219 : template<typename _Tp, typename _Up>
1220 : using __optional_le_t = __optional_relop_t<
1221 : decltype(std::declval<const _Tp&>() <= std::declval<const _Up&>())
1222 : >;
1223 :
1224 : template<typename _Tp, typename _Up>
1225 : using __optional_ge_t = __optional_relop_t<
1226 : decltype(std::declval<const _Tp&>() >= std::declval<const _Up&>())
1227 : >;
1228 :
1229 : // Comparisons between optional values.
1230 : template<typename _Tp, typename _Up>
1231 : constexpr auto
1232 : operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1233 : -> __optional_eq_t<_Tp, _Up>
1234 : {
1235 : return static_cast<bool>(__lhs) == static_cast<bool>(__rhs)
1236 : && (!__lhs || *__lhs == *__rhs);
1237 : }
1238 :
1239 : template<typename _Tp, typename _Up>
1240 : constexpr auto
1241 : operator!=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1242 : -> __optional_ne_t<_Tp, _Up>
1243 : {
1244 : return static_cast<bool>(__lhs) != static_cast<bool>(__rhs)
1245 : || (static_cast<bool>(__lhs) && *__lhs != *__rhs);
1246 : }
1247 :
1248 : template<typename _Tp, typename _Up>
1249 : constexpr auto
1250 : operator<(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1251 : -> __optional_lt_t<_Tp, _Up>
1252 : {
1253 : return static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs);
1254 : }
1255 :
1256 : template<typename _Tp, typename _Up>
1257 : constexpr auto
1258 : operator>(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1259 : -> __optional_gt_t<_Tp, _Up>
1260 : {
1261 : return static_cast<bool>(__lhs) && (!__rhs || *__lhs > *__rhs);
1262 : }
1263 :
1264 : template<typename _Tp, typename _Up>
1265 : constexpr auto
1266 : operator<=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1267 : -> __optional_le_t<_Tp, _Up>
1268 : {
1269 : return !__lhs || (static_cast<bool>(__rhs) && *__lhs <= *__rhs);
1270 : }
1271 :
1272 : template<typename _Tp, typename _Up>
1273 : constexpr auto
1274 : operator>=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1275 : -> __optional_ge_t<_Tp, _Up>
1276 : {
1277 : return !__rhs || (static_cast<bool>(__lhs) && *__lhs >= *__rhs);
1278 : }
1279 :
1280 : #ifdef __cpp_lib_three_way_comparison
1281 : template<typename _Tp, three_way_comparable_with<_Tp> _Up>
1282 : constexpr compare_three_way_result_t<_Tp, _Up>
1283 : operator<=>(const optional<_Tp>& __x, const optional<_Up>& __y)
1284 : {
1285 : return __x && __y ? *__x <=> *__y : bool(__x) <=> bool(__y);
1286 : }
1287 : #endif
1288 :
1289 : // Comparisons with nullopt.
1290 : template<typename _Tp>
1291 : constexpr bool
1292 : operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
1293 : { return !__lhs; }
1294 :
1295 : #ifdef __cpp_lib_three_way_comparison
1296 : template<typename _Tp>
1297 : constexpr strong_ordering
1298 : operator<=>(const optional<_Tp>& __x, nullopt_t) noexcept
1299 : { return bool(__x) <=> false; }
1300 : #else
1301 : template<typename _Tp>
1302 : constexpr bool
1303 : operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
1304 : { return !__rhs; }
1305 :
1306 : template<typename _Tp>
1307 : constexpr bool
1308 : operator!=(const optional<_Tp>& __lhs, nullopt_t) noexcept
1309 : { return static_cast<bool>(__lhs); }
1310 :
1311 : template<typename _Tp>
1312 : constexpr bool
1313 : operator!=(nullopt_t, const optional<_Tp>& __rhs) noexcept
1314 : { return static_cast<bool>(__rhs); }
1315 :
1316 : template<typename _Tp>
1317 : constexpr bool
1318 : operator<(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
1319 : { return false; }
1320 :
1321 : template<typename _Tp>
1322 : constexpr bool
1323 : operator<(nullopt_t, const optional<_Tp>& __rhs) noexcept
1324 : { return static_cast<bool>(__rhs); }
1325 :
1326 : template<typename _Tp>
1327 : constexpr bool
1328 : operator>(const optional<_Tp>& __lhs, nullopt_t) noexcept
1329 : { return static_cast<bool>(__lhs); }
1330 :
1331 : template<typename _Tp>
1332 : constexpr bool
1333 : operator>(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
1334 : { return false; }
1335 :
1336 : template<typename _Tp>
1337 : constexpr bool
1338 : operator<=(const optional<_Tp>& __lhs, nullopt_t) noexcept
1339 : { return !__lhs; }
1340 :
1341 : template<typename _Tp>
1342 : constexpr bool
1343 : operator<=(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
1344 : { return true; }
1345 :
1346 : template<typename _Tp>
1347 : constexpr bool
1348 : operator>=(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
1349 : { return true; }
1350 :
1351 : template<typename _Tp>
1352 : constexpr bool
1353 : operator>=(nullopt_t, const optional<_Tp>& __rhs) noexcept
1354 : { return !__rhs; }
1355 : #endif // three-way-comparison
1356 :
1357 : // Comparisons with value type.
1358 : template<typename _Tp, typename _Up>
1359 : constexpr auto
1360 : operator==(const optional<_Tp>& __lhs, const _Up& __rhs)
1361 : -> __optional_eq_t<_Tp, _Up>
1362 : { return __lhs && *__lhs == __rhs; }
1363 :
1364 : template<typename _Tp, typename _Up>
1365 : constexpr auto
1366 : operator==(const _Up& __lhs, const optional<_Tp>& __rhs)
1367 : -> __optional_eq_t<_Up, _Tp>
1368 : { return __rhs && __lhs == *__rhs; }
1369 :
1370 : template<typename _Tp, typename _Up>
1371 : constexpr auto
1372 : operator!=(const optional<_Tp>& __lhs, const _Up& __rhs)
1373 : -> __optional_ne_t<_Tp, _Up>
1374 : { return !__lhs || *__lhs != __rhs; }
1375 :
1376 : template<typename _Tp, typename _Up>
1377 : constexpr auto
1378 : operator!=(const _Up& __lhs, const optional<_Tp>& __rhs)
1379 : -> __optional_ne_t<_Up, _Tp>
1380 : { return !__rhs || __lhs != *__rhs; }
1381 :
1382 : template<typename _Tp, typename _Up>
1383 : constexpr auto
1384 : operator<(const optional<_Tp>& __lhs, const _Up& __rhs)
1385 : -> __optional_lt_t<_Tp, _Up>
1386 : { return !__lhs || *__lhs < __rhs; }
1387 :
1388 : template<typename _Tp, typename _Up>
1389 : constexpr auto
1390 : operator<(const _Up& __lhs, const optional<_Tp>& __rhs)
1391 : -> __optional_lt_t<_Up, _Tp>
1392 : { return __rhs && __lhs < *__rhs; }
1393 :
1394 : template<typename _Tp, typename _Up>
1395 : constexpr auto
1396 : operator>(const optional<_Tp>& __lhs, const _Up& __rhs)
1397 : -> __optional_gt_t<_Tp, _Up>
1398 : { return __lhs && *__lhs > __rhs; }
1399 :
1400 : template<typename _Tp, typename _Up>
1401 : constexpr auto
1402 : operator>(const _Up& __lhs, const optional<_Tp>& __rhs)
1403 : -> __optional_gt_t<_Up, _Tp>
1404 : { return !__rhs || __lhs > *__rhs; }
1405 :
1406 : template<typename _Tp, typename _Up>
1407 : constexpr auto
1408 : operator<=(const optional<_Tp>& __lhs, const _Up& __rhs)
1409 : -> __optional_le_t<_Tp, _Up>
1410 : { return !__lhs || *__lhs <= __rhs; }
1411 :
1412 : template<typename _Tp, typename _Up>
1413 : constexpr auto
1414 : operator<=(const _Up& __lhs, const optional<_Tp>& __rhs)
1415 : -> __optional_le_t<_Up, _Tp>
1416 : { return __rhs && __lhs <= *__rhs; }
1417 :
1418 : template<typename _Tp, typename _Up>
1419 : constexpr auto
1420 : operator>=(const optional<_Tp>& __lhs, const _Up& __rhs)
1421 : -> __optional_ge_t<_Tp, _Up>
1422 : { return __lhs && *__lhs >= __rhs; }
1423 :
1424 : template<typename _Tp, typename _Up>
1425 : constexpr auto
1426 : operator>=(const _Up& __lhs, const optional<_Tp>& __rhs)
1427 : -> __optional_ge_t<_Up, _Tp>
1428 : { return !__rhs || __lhs >= *__rhs; }
1429 :
1430 : #ifdef __cpp_lib_three_way_comparison
1431 : template<typename _Tp, typename _Up>
1432 : requires (!__is_optional_v<_Up>)
1433 : && three_way_comparable_with<_Up, _Tp>
1434 : constexpr compare_three_way_result_t<_Tp, _Up>
1435 : operator<=>(const optional<_Tp>& __x, const _Up& __v)
1436 : { return bool(__x) ? *__x <=> __v : strong_ordering::less; }
1437 : #endif
1438 :
1439 : // Swap and creation functions.
1440 :
1441 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
1442 : // 2748. swappable traits for optionals
1443 : template<typename _Tp>
1444 : _GLIBCXX20_CONSTEXPR
1445 : inline enable_if_t<is_move_constructible_v<_Tp> && is_swappable_v<_Tp>>
1446 : swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs)
1447 : noexcept(noexcept(__lhs.swap(__rhs)))
1448 : { __lhs.swap(__rhs); }
1449 :
1450 : template<typename _Tp>
1451 : enable_if_t<!(is_move_constructible_v<_Tp> && is_swappable_v<_Tp>)>
1452 : swap(optional<_Tp>&, optional<_Tp>&) = delete;
1453 :
1454 : template<typename _Tp>
1455 : constexpr
1456 : enable_if_t<is_constructible_v<decay_t<_Tp>, _Tp>,
1457 : optional<decay_t<_Tp>>>
1458 : make_optional(_Tp&& __t)
1459 : noexcept(is_nothrow_constructible_v<optional<decay_t<_Tp>>, _Tp>)
1460 : { return optional<decay_t<_Tp>>{ std::forward<_Tp>(__t) }; }
1461 :
1462 : template<typename _Tp, typename... _Args>
1463 : constexpr
1464 : enable_if_t<is_constructible_v<_Tp, _Args...>,
1465 : optional<_Tp>>
1466 : make_optional(_Args&&... __args)
1467 : noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
1468 : { return optional<_Tp>{ in_place, std::forward<_Args>(__args)... }; }
1469 :
1470 : template<typename _Tp, typename _Up, typename... _Args>
1471 : constexpr
1472 : enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1473 : optional<_Tp>>
1474 : make_optional(initializer_list<_Up> __il, _Args&&... __args)
1475 : noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1476 : { return optional<_Tp>{ in_place, __il, std::forward<_Args>(__args)... }; }
1477 :
1478 : // Hash.
1479 :
1480 : template<typename _Tp, typename _Up = remove_const_t<_Tp>,
1481 : bool = __poison_hash<_Up>::__enable_hash_call>
1482 : struct __optional_hash_call_base
1483 : {
1484 : size_t
1485 : operator()(const optional<_Tp>& __t) const
1486 : noexcept(noexcept(hash<_Up>{}(*__t)))
1487 : {
1488 : // We pick an arbitrary hash for disengaged optionals which hopefully
1489 : // usual values of _Tp won't typically hash to.
1490 : constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333);
1491 : return __t ? hash<_Up>{}(*__t) : __magic_disengaged_hash;
1492 : }
1493 : };
1494 :
1495 : template<typename _Tp, typename _Up>
1496 : struct __optional_hash_call_base<_Tp, _Up, false> {};
1497 :
1498 : template<typename _Tp>
1499 : struct hash<optional<_Tp>>
1500 : : private __poison_hash<remove_const_t<_Tp>>,
1501 : public __optional_hash_call_base<_Tp>
1502 : {
1503 : using result_type [[__deprecated__]] = size_t;
1504 : using argument_type [[__deprecated__]] = optional<_Tp>;
1505 : };
1506 :
1507 : template<typename _Tp>
1508 : struct __is_fast_hash<hash<optional<_Tp>>> : __is_fast_hash<hash<_Tp>>
1509 : { };
1510 :
1511 : /// @}
1512 :
1513 : #if __cpp_deduction_guides >= 201606
1514 : template <typename _Tp> optional(_Tp) -> optional<_Tp>;
1515 : #endif
1516 :
1517 : _GLIBCXX_END_NAMESPACE_VERSION
1518 : } // namespace std
1519 :
1520 : #endif // __cpp_lib_optional
1521 :
1522 : #endif // _GLIBCXX_OPTIONAL
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