source: Daodan/MSYS2/mingw32/include/c++/11.2.0/experimental/optional@ 1177

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1// <optional> -*- C++ -*-
2
3// Copyright (C) 2013-2021 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file experimental/optional
26 * This is a TS C++ Library header.
27 * @ingroup libfund-ts
28 */
29
30#ifndef _GLIBCXX_EXPERIMENTAL_OPTIONAL
31#define _GLIBCXX_EXPERIMENTAL_OPTIONAL 1
32
33#if __cplusplus >= 201402L
34
35#include <utility>
36#include <type_traits>
37#include <stdexcept>
38#include <new>
39#include <initializer_list>
40#include <bits/functexcept.h>
41#include <bits/functional_hash.h>
42#include <bits/enable_special_members.h>
43#include <experimental/bits/lfts_config.h>
44
45namespace std _GLIBCXX_VISIBILITY(default)
46{
47_GLIBCXX_BEGIN_NAMESPACE_VERSION
48
49namespace experimental
50{
51inline namespace fundamentals_v1
52{
53 /**
54 * @defgroup optional Optional values
55 * @ingroup libfund-ts
56 *
57 * Class template for optional values and surrounding facilities, as
58 * described in n3793 "A proposal to add a utility class to represent
59 * optional objects (Revision 5)".
60 *
61 * @{
62 */
63
64#define __cpp_lib_experimental_optional 201411
65
66 // All subsequent [X.Y.n] references are against n3793.
67
68 // [X.Y.4]
69 template<typename _Tp>
70 class optional;
71
72 // [X.Y.5]
73 /// Tag type for in-place construction.
74 struct in_place_t { };
75
76 /// Tag for in-place construction.
77 constexpr in_place_t in_place { };
78
79 // [X.Y.6]
80 /// Tag type to disengage optional objects.
81 struct nullopt_t
82 {
83 // Do not user-declare default constructor at all for
84 // optional_value = {} syntax to work.
85 // nullopt_t() = delete;
86
87 // Used for constructing nullopt.
88 enum class _Construct { _Token };
89
90 // Must be constexpr for nullopt_t to be literal.
91 explicit constexpr nullopt_t(_Construct) { }
92 };
93
94 // [X.Y.6]
95 /// Tag to disengage optional objects.
96 constexpr nullopt_t nullopt { nullopt_t::_Construct::_Token };
97
98 // [X.Y.7]
99 /**
100 * @brief Exception class thrown when a disengaged optional object is
101 * dereferenced.
102 * @ingroup exceptions
103 */
104 class bad_optional_access : public logic_error
105 {
106 public:
107 bad_optional_access() : logic_error("bad optional access") { }
108
109 // XXX This constructor is non-standard. Should not be inline
110 explicit bad_optional_access(const char* __arg) : logic_error(__arg) { }
111
112 virtual ~bad_optional_access() noexcept = default;
113 };
114
115 /// @cond undocumented
116
117 void
118 __throw_bad_optional_access(const char*)
119 __attribute__((__noreturn__));
120
121 // XXX Does not belong here.
122 inline void
123 __throw_bad_optional_access(const char* __s)
124 { _GLIBCXX_THROW_OR_ABORT(bad_optional_access(__s)); }
125
126 /**
127 * @brief Class template that holds the necessary state for @ref optional
128 * and that has the responsibility for construction and the special members.
129 *
130 * Such a separate base class template is necessary in order to
131 * conditionally enable the special members (e.g. copy/move constructors).
132 * Note that this means that @ref _Optional_base implements the
133 * functionality for copy and move assignment, but not for converting
134 * assignment.
135 *
136 * @see optional, _Enable_special_members
137 */
138 template<typename _Tp, bool _ShouldProvideDestructor =
139 !is_trivially_destructible<_Tp>::value>
140 class _Optional_base
141 {
142 private:
143 // Remove const to avoid prohibition of reusing object storage for
144 // const-qualified types in [3.8/9]. This is strictly internal
145 // and even optional itself is oblivious to it.
146 using _Stored_type = remove_const_t<_Tp>;
147
148 public:
149 // [X.Y.4.1] Constructors.
150
151 // Constructors for disengaged optionals.
152 constexpr _Optional_base() noexcept
153 : _M_empty{} { }
154
155 constexpr _Optional_base(nullopt_t) noexcept
156 : _Optional_base{} { }
157
158 // Constructors for engaged optionals.
159 template<typename... _Args>
160 constexpr explicit _Optional_base(in_place_t, _Args&&... __args)
161 : _M_payload(std::forward<_Args>(__args)...), _M_engaged(true) { }
162
163 template<typename _Up, typename... _Args,
164 enable_if_t<is_constructible<_Tp,
165 initializer_list<_Up>&,
166 _Args&&...>::value,
167 int>...>
168 constexpr explicit _Optional_base(in_place_t,
169 initializer_list<_Up> __il,
170 _Args&&... __args)
171 : _M_payload(__il, std::forward<_Args>(__args)...),
172 _M_engaged(true) { }
173
174 // Copy and move constructors.
175 _Optional_base(const _Optional_base& __other)
176 {
177 if (__other._M_engaged)
178 this->_M_construct(__other._M_get());
179 }
180
181 _Optional_base(_Optional_base&& __other)
182 noexcept(is_nothrow_move_constructible<_Tp>())
183 {
184 if (__other._M_engaged)
185 this->_M_construct(std::move(__other._M_get()));
186 }
187
188 // [X.Y.4.3] (partly) Assignment.
189 _Optional_base&
190 operator=(const _Optional_base& __other)
191 {
192 if (this->_M_engaged && __other._M_engaged)
193 this->_M_get() = __other._M_get();
194 else
195 {
196 if (__other._M_engaged)
197 this->_M_construct(__other._M_get());
198 else
199 this->_M_reset();
200 }
201
202 return *this;
203 }
204
205 _Optional_base&
206 operator=(_Optional_base&& __other)
207 noexcept(__and_<is_nothrow_move_constructible<_Tp>,
208 is_nothrow_move_assignable<_Tp>>())
209 {
210 if (this->_M_engaged && __other._M_engaged)
211 this->_M_get() = std::move(__other._M_get());
212 else
213 {
214 if (__other._M_engaged)
215 this->_M_construct(std::move(__other._M_get()));
216 else
217 this->_M_reset();
218 }
219 return *this;
220 }
221
222 // [X.Y.4.2] Destructor.
223 ~_Optional_base()
224 {
225 if (this->_M_engaged)
226 this->_M_payload.~_Stored_type();
227 }
228
229 // The following functionality is also needed by optional, hence the
230 // protected accessibility.
231 protected:
232 constexpr bool _M_is_engaged() const noexcept
233 { return this->_M_engaged; }
234
235 // The _M_get operations have _M_engaged as a precondition.
236 constexpr _Tp&
237 _M_get() noexcept
238 { return _M_payload; }
239
240 constexpr const _Tp&
241 _M_get() const noexcept
242 { return _M_payload; }
243
244 // The _M_construct operation has !_M_engaged as a precondition
245 // while _M_destruct has _M_engaged as a precondition.
246 template<typename... _Args>
247 void
248 _M_construct(_Args&&... __args)
249 noexcept(is_nothrow_constructible<_Stored_type, _Args...>())
250 {
251 ::new (std::__addressof(this->_M_payload))
252 _Stored_type(std::forward<_Args>(__args)...);
253 this->_M_engaged = true;
254 }
255
256 void
257 _M_destruct()
258 {
259 this->_M_engaged = false;
260 this->_M_payload.~_Stored_type();
261 }
262
263 // _M_reset is a 'safe' operation with no precondition.
264 void
265 _M_reset()
266 {
267 if (this->_M_engaged)
268 this->_M_destruct();
269 }
270
271 private:
272 struct _Empty_byte { };
273 union {
274 _Empty_byte _M_empty;
275 _Stored_type _M_payload;
276 };
277 bool _M_engaged = false;
278 };
279
280 /// Partial specialization that is exactly identical to the primary template
281 /// save for not providing a destructor, to fulfill triviality requirements.
282 template<typename _Tp>
283 class _Optional_base<_Tp, false>
284 {
285 private:
286 using _Stored_type = remove_const_t<_Tp>;
287
288 public:
289 constexpr _Optional_base() noexcept
290 : _M_empty{} { }
291
292 constexpr _Optional_base(nullopt_t) noexcept
293 : _Optional_base{} { }
294
295 template<typename... _Args>
296 constexpr explicit _Optional_base(in_place_t, _Args&&... __args)
297 : _M_payload(std::forward<_Args>(__args)...), _M_engaged(true) { }
298
299 template<typename _Up, typename... _Args,
300 enable_if_t<is_constructible<_Tp,
301 initializer_list<_Up>&,
302 _Args&&...>::value,
303 int>...>
304 constexpr explicit _Optional_base(in_place_t,
305 initializer_list<_Up> __il,
306 _Args&&... __args)
307 : _M_payload(__il, std::forward<_Args>(__args)...),
308 _M_engaged(true) { }
309
310 _Optional_base(const _Optional_base& __other)
311 {
312 if (__other._M_engaged)
313 this->_M_construct(__other._M_get());
314 }
315
316 _Optional_base(_Optional_base&& __other)
317 noexcept(is_nothrow_move_constructible<_Tp>())
318 {
319 if (__other._M_engaged)
320 this->_M_construct(std::move(__other._M_get()));
321 }
322
323 _Optional_base&
324 operator=(const _Optional_base& __other)
325 {
326 if (this->_M_engaged && __other._M_engaged)
327 this->_M_get() = __other._M_get();
328 else
329 {
330 if (__other._M_engaged)
331 this->_M_construct(__other._M_get());
332 else
333 this->_M_reset();
334 }
335 return *this;
336 }
337
338 _Optional_base&
339 operator=(_Optional_base&& __other)
340 noexcept(__and_<is_nothrow_move_constructible<_Tp>,
341 is_nothrow_move_assignable<_Tp>>())
342 {
343 if (this->_M_engaged && __other._M_engaged)
344 this->_M_get() = std::move(__other._M_get());
345 else
346 {
347 if (__other._M_engaged)
348 this->_M_construct(std::move(__other._M_get()));
349 else
350 this->_M_reset();
351 }
352 return *this;
353 }
354
355 // Sole difference
356 // ~_Optional_base() noexcept = default;
357
358 protected:
359 constexpr bool _M_is_engaged() const noexcept
360 { return this->_M_engaged; }
361
362 _Tp&
363 _M_get() noexcept
364 { return _M_payload; }
365
366 constexpr const _Tp&
367 _M_get() const noexcept
368 { return _M_payload; }
369
370 template<typename... _Args>
371 void
372 _M_construct(_Args&&... __args)
373 noexcept(is_nothrow_constructible<_Stored_type, _Args...>())
374 {
375 ::new (std::__addressof(this->_M_payload))
376 _Stored_type(std::forward<_Args>(__args)...);
377 this->_M_engaged = true;
378 }
379
380 void
381 _M_destruct()
382 {
383 this->_M_engaged = false;
384 this->_M_payload.~_Stored_type();
385 }
386
387 void
388 _M_reset()
389 {
390 if (this->_M_engaged)
391 this->_M_destruct();
392 }
393
394 private:
395 struct _Empty_byte { };
396 union
397 {
398 _Empty_byte _M_empty;
399 _Stored_type _M_payload;
400 };
401 bool _M_engaged = false;
402 };
403
404 template<typename _Tp, typename _Up>
405 using __converts_from_optional =
406 __or_<is_constructible<_Tp, const optional<_Up>&>,
407 is_constructible<_Tp, optional<_Up>&>,
408 is_constructible<_Tp, const optional<_Up>&&>,
409 is_constructible<_Tp, optional<_Up>&&>,
410 is_convertible<const optional<_Up>&, _Tp>,
411 is_convertible<optional<_Up>&, _Tp>,
412 is_convertible<const optional<_Up>&&, _Tp>,
413 is_convertible<optional<_Up>&&, _Tp>>;
414
415 template<typename _Tp, typename _Up>
416 using __assigns_from_optional =
417 __or_<is_assignable<_Tp&, const optional<_Up>&>,
418 is_assignable<_Tp&, optional<_Up>&>,
419 is_assignable<_Tp&, const optional<_Up>&&>,
420 is_assignable<_Tp&, optional<_Up>&&>>;
421
422 /// @endcond
423
424 /**
425 * @brief Class template for optional values.
426 */
427 template<typename _Tp>
428 class optional
429 : private _Optional_base<_Tp>,
430 private _Enable_copy_move<
431 // Copy constructor.
432 is_copy_constructible<_Tp>::value,
433 // Copy assignment.
434 __and_<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>::value,
435 // Move constructor.
436 is_move_constructible<_Tp>::value,
437 // Move assignment.
438 __and_<is_move_constructible<_Tp>, is_move_assignable<_Tp>>::value,
439 // Unique tag type.
440 optional<_Tp>>
441 {
442 static_assert(__and_<__not_<is_same<remove_cv_t<_Tp>, nullopt_t>>,
443 __not_<is_same<remove_cv_t<_Tp>, in_place_t>>,
444 __not_<is_reference<_Tp>>>(),
445 "Invalid instantiation of optional<T>");
446
447 private:
448 using _Base = _Optional_base<_Tp>;
449
450 public:
451 using value_type = _Tp;
452
453 // _Optional_base has the responsibility for construction.
454 using _Base::_Base;
455
456 constexpr optional() = default;
457 // Converting constructors for engaged optionals.
458 template <typename _Up = _Tp,
459 enable_if_t<__and_<
460 __not_<is_same<optional<_Tp>, decay_t<_Up>>>,
461 is_constructible<_Tp, _Up&&>,
462 is_convertible<_Up&&, _Tp>
463 >::value, bool> = true>
464 constexpr optional(_Up&& __t)
465 : _Base(in_place, std::forward<_Up>(__t)) { }
466
467 template <typename _Up = _Tp,
468 enable_if_t<__and_<
469 __not_<is_same<optional<_Tp>, decay_t<_Up>>>,
470 is_constructible<_Tp, _Up&&>,
471 __not_<is_convertible<_Up&&, _Tp>>
472 >::value, bool> = false>
473 explicit constexpr optional(_Up&& __t)
474 : _Base(in_place, std::forward<_Up>(__t)) { }
475
476 template <typename _Up,
477 enable_if_t<__and_<
478 __not_<is_same<_Tp, _Up>>,
479 is_constructible<_Tp, const _Up&>,
480 is_convertible<const _Up&, _Tp>,
481 __not_<__converts_from_optional<_Tp, _Up>>
482 >::value, bool> = true>
483 constexpr optional(const optional<_Up>& __t)
484 {
485 if (__t)
486 emplace(*__t);
487 }
488
489 template <typename _Up,
490 enable_if_t<__and_<
491 __not_<is_same<_Tp, _Up>>,
492 is_constructible<_Tp, const _Up&>,
493 __not_<is_convertible<const _Up&, _Tp>>,
494 __not_<__converts_from_optional<_Tp, _Up>>
495 >::value, bool> = false>
496 explicit constexpr optional(const optional<_Up>& __t)
497 {
498 if (__t)
499 emplace(*__t);
500 }
501
502 template <typename _Up,
503 enable_if_t<__and_<
504 __not_<is_same<_Tp, _Up>>,
505 is_constructible<_Tp, _Up&&>,
506 is_convertible<_Up&&, _Tp>,
507 __not_<__converts_from_optional<_Tp, _Up>>
508 >::value, bool> = true>
509 constexpr optional(optional<_Up>&& __t)
510 {
511 if (__t)
512 emplace(std::move(*__t));
513 }
514
515 template <typename _Up,
516 enable_if_t<__and_<
517 __not_<is_same<_Tp, _Up>>,
518 is_constructible<_Tp, _Up&&>,
519 __not_<is_convertible<_Up&&, _Tp>>,
520 __not_<__converts_from_optional<_Tp, _Up>>
521 >::value, bool> = false>
522 explicit constexpr optional(optional<_Up>&& __t)
523 {
524 if (__t)
525 emplace(std::move(*__t));
526 }
527
528 // [X.Y.4.3] (partly) Assignment.
529 optional&
530 operator=(nullopt_t) noexcept
531 {
532 this->_M_reset();
533 return *this;
534 }
535
536 template<typename _Up = _Tp>
537 enable_if_t<__and_<
538 __not_<is_same<optional<_Tp>, decay_t<_Up>>>,
539 is_constructible<_Tp, _Up>,
540 __not_<__and_<is_scalar<_Tp>,
541 is_same<_Tp, decay_t<_Up>>>>,
542 is_assignable<_Tp&, _Up>>::value,
543 optional&>
544 operator=(_Up&& __u)
545 {
546 if (this->_M_is_engaged())
547 this->_M_get() = std::forward<_Up>(__u);
548 else
549 this->_M_construct(std::forward<_Up>(__u));
550
551 return *this;
552 }
553
554 template<typename _Up>
555 enable_if_t<__and_<
556 __not_<is_same<_Tp, _Up>>,
557 is_constructible<_Tp, const _Up&>,
558 is_assignable<_Tp&, _Up>,
559 __not_<__converts_from_optional<_Tp, _Up>>,
560 __not_<__assigns_from_optional<_Tp, _Up>>
561 >::value,
562 optional&>
563 operator=(const optional<_Up>& __u)
564 {
565 if (__u)
566 {
567 if (this->_M_is_engaged())
568 this->_M_get() = *__u;
569 else
570 this->_M_construct(*__u);
571 }
572 else
573 {
574 this->_M_reset();
575 }
576 return *this;
577 }
578
579 template<typename _Up>
580 enable_if_t<__and_<
581 __not_<is_same<_Tp, _Up>>,
582 is_constructible<_Tp, _Up>,
583 is_assignable<_Tp&, _Up>,
584 __not_<__converts_from_optional<_Tp, _Up>>,
585 __not_<__assigns_from_optional<_Tp, _Up>>
586 >::value,
587 optional&>
588 operator=(optional<_Up>&& __u)
589 {
590 if (__u)
591 {
592 if (this->_M_is_engaged())
593 this->_M_get() = std::move(*__u);
594 else
595 this->_M_construct(std::move(*__u));
596 }
597 else
598 {
599 this->_M_reset();
600 }
601
602 return *this;
603 }
604
605 template<typename... _Args>
606 enable_if_t<is_constructible<_Tp, _Args&&...>::value>
607 emplace(_Args&&... __args)
608 {
609 this->_M_reset();
610 this->_M_construct(std::forward<_Args>(__args)...);
611 }
612
613 template<typename _Up, typename... _Args>
614 enable_if_t<is_constructible<_Tp, initializer_list<_Up>&,
615 _Args&&...>::value>
616 emplace(initializer_list<_Up> __il, _Args&&... __args)
617 {
618 this->_M_reset();
619 this->_M_construct(__il, std::forward<_Args>(__args)...);
620 }
621
622 // [X.Y.4.2] Destructor is implicit, implemented in _Optional_base.
623
624 // [X.Y.4.4] Swap.
625 void
626 swap(optional& __other)
627 noexcept(is_nothrow_move_constructible<_Tp>()
628 && __is_nothrow_swappable<_Tp>::value)
629 {
630 using std::swap;
631
632 if (this->_M_is_engaged() && __other._M_is_engaged())
633 swap(this->_M_get(), __other._M_get());
634 else if (this->_M_is_engaged())
635 {
636 __other._M_construct(std::move(this->_M_get()));
637 this->_M_destruct();
638 }
639 else if (__other._M_is_engaged())
640 {
641 this->_M_construct(std::move(__other._M_get()));
642 __other._M_destruct();
643 }
644 }
645
646 // [X.Y.4.5] Observers.
647 constexpr const _Tp*
648 operator->() const
649 { return std::__addressof(this->_M_get()); }
650
651 _Tp*
652 operator->()
653 { return std::__addressof(this->_M_get()); }
654
655 constexpr const _Tp&
656 operator*() const&
657 { return this->_M_get(); }
658
659 constexpr _Tp&
660 operator*()&
661 { return this->_M_get(); }
662
663 constexpr _Tp&&
664 operator*()&&
665 { return std::move(this->_M_get()); }
666
667 constexpr const _Tp&&
668 operator*() const&&
669 { return std::move(this->_M_get()); }
670
671 constexpr explicit operator bool() const noexcept
672 { return this->_M_is_engaged(); }
673
674 constexpr const _Tp&
675 value() const&
676 {
677 return this->_M_is_engaged()
678 ? this->_M_get()
679 : (__throw_bad_optional_access("Attempt to access value of a "
680 "disengaged optional object"),
681 this->_M_get());
682 }
683
684 constexpr _Tp&
685 value()&
686 {
687 return this->_M_is_engaged()
688 ? this->_M_get()
689 : (__throw_bad_optional_access("Attempt to access value of a "
690 "disengaged optional object"),
691 this->_M_get());
692 }
693
694 constexpr _Tp&&
695 value()&&
696 {
697 return this->_M_is_engaged()
698 ? std::move(this->_M_get())
699 : (__throw_bad_optional_access("Attempt to access value of a "
700 "disengaged optional object"),
701 std::move(this->_M_get()));
702 }
703
704 constexpr const _Tp&&
705 value() const&&
706 {
707 return this->_M_is_engaged()
708 ? std::move(this->_M_get())
709 : (__throw_bad_optional_access("Attempt to access value of a "
710 "disengaged optional object"),
711 std::move(this->_M_get()));
712 }
713
714 template<typename _Up>
715 constexpr _Tp
716 value_or(_Up&& __u) const&
717 {
718 static_assert(__and_<is_copy_constructible<_Tp>,
719 is_convertible<_Up&&, _Tp>>(),
720 "Cannot return value");
721
722 return this->_M_is_engaged()
723 ? this->_M_get()
724 : static_cast<_Tp>(std::forward<_Up>(__u));
725 }
726
727 template<typename _Up>
728 _Tp
729 value_or(_Up&& __u) &&
730 {
731 static_assert(__and_<is_move_constructible<_Tp>,
732 is_convertible<_Up&&, _Tp>>(),
733 "Cannot return value" );
734
735 return this->_M_is_engaged()
736 ? std::move(this->_M_get())
737 : static_cast<_Tp>(std::forward<_Up>(__u));
738 }
739 };
740
741 /// @relates experimental::optional @{
742
743 // [X.Y.8] Comparisons between optional values.
744 template<typename _Tp>
745 constexpr bool
746 operator==(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
747 {
748 return static_cast<bool>(__lhs) == static_cast<bool>(__rhs)
749 && (!__lhs || *__lhs == *__rhs);
750 }
751
752 template<typename _Tp>
753 constexpr bool
754 operator!=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
755 { return !(__lhs == __rhs); }
756
757 template<typename _Tp>
758 constexpr bool
759 operator<(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
760 {
761 return static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs);
762 }
763
764 template<typename _Tp>
765 constexpr bool
766 operator>(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
767 { return __rhs < __lhs; }
768
769 template<typename _Tp>
770 constexpr bool
771 operator<=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
772 { return !(__rhs < __lhs); }
773
774 template<typename _Tp>
775 constexpr bool
776 operator>=(const optional<_Tp>& __lhs, const optional<_Tp>& __rhs)
777 { return !(__lhs < __rhs); }
778
779 // [X.Y.9] Comparisons with nullopt.
780 template<typename _Tp>
781 constexpr bool
782 operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
783 { return !__lhs; }
784
785 template<typename _Tp>
786 constexpr bool
787 operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
788 { return !__rhs; }
789
790 template<typename _Tp>
791 constexpr bool
792 operator!=(const optional<_Tp>& __lhs, nullopt_t) noexcept
793 { return static_cast<bool>(__lhs); }
794
795 template<typename _Tp>
796 constexpr bool
797 operator!=(nullopt_t, const optional<_Tp>& __rhs) noexcept
798 { return static_cast<bool>(__rhs); }
799
800 template<typename _Tp>
801 constexpr bool
802 operator<(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
803 { return false; }
804
805 template<typename _Tp>
806 constexpr bool
807 operator<(nullopt_t, const optional<_Tp>& __rhs) noexcept
808 { return static_cast<bool>(__rhs); }
809
810 template<typename _Tp>
811 constexpr bool
812 operator>(const optional<_Tp>& __lhs, nullopt_t) noexcept
813 { return static_cast<bool>(__lhs); }
814
815 template<typename _Tp>
816 constexpr bool
817 operator>(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
818 { return false; }
819
820 template<typename _Tp>
821 constexpr bool
822 operator<=(const optional<_Tp>& __lhs, nullopt_t) noexcept
823 { return !__lhs; }
824
825 template<typename _Tp>
826 constexpr bool
827 operator<=(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
828 { return true; }
829
830 template<typename _Tp>
831 constexpr bool
832 operator>=(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
833 { return true; }
834
835 template<typename _Tp>
836 constexpr bool
837 operator>=(nullopt_t, const optional<_Tp>& __rhs) noexcept
838 { return !__rhs; }
839
840 // [X.Y.10] Comparisons with value type.
841 template<typename _Tp>
842 constexpr bool
843 operator==(const optional<_Tp>& __lhs, const _Tp& __rhs)
844 { return __lhs && *__lhs == __rhs; }
845
846 template<typename _Tp>
847 constexpr bool
848 operator==(const _Tp& __lhs, const optional<_Tp>& __rhs)
849 { return __rhs && __lhs == *__rhs; }
850
851 template<typename _Tp>
852 constexpr bool
853 operator!=(const optional<_Tp>& __lhs, _Tp const& __rhs)
854 { return !__lhs || !(*__lhs == __rhs); }
855
856 template<typename _Tp>
857 constexpr bool
858 operator!=(const _Tp& __lhs, const optional<_Tp>& __rhs)
859 { return !__rhs || !(__lhs == *__rhs); }
860
861 template<typename _Tp>
862 constexpr bool
863 operator<(const optional<_Tp>& __lhs, const _Tp& __rhs)
864 { return !__lhs || *__lhs < __rhs; }
865
866 template<typename _Tp>
867 constexpr bool
868 operator<(const _Tp& __lhs, const optional<_Tp>& __rhs)
869 { return __rhs && __lhs < *__rhs; }
870
871 template<typename _Tp>
872 constexpr bool
873 operator>(const optional<_Tp>& __lhs, const _Tp& __rhs)
874 { return __lhs && __rhs < *__lhs; }
875
876 template<typename _Tp>
877 constexpr bool
878 operator>(const _Tp& __lhs, const optional<_Tp>& __rhs)
879 { return !__rhs || *__rhs < __lhs; }
880
881 template<typename _Tp>
882 constexpr bool
883 operator<=(const optional<_Tp>& __lhs, const _Tp& __rhs)
884 { return !__lhs || !(__rhs < *__lhs); }
885
886 template<typename _Tp>
887 constexpr bool
888 operator<=(const _Tp& __lhs, const optional<_Tp>& __rhs)
889 { return __rhs && !(*__rhs < __lhs); }
890
891 template<typename _Tp>
892 constexpr bool
893 operator>=(const optional<_Tp>& __lhs, const _Tp& __rhs)
894 { return __lhs && !(*__lhs < __rhs); }
895
896 template<typename _Tp>
897 constexpr bool
898 operator>=(const _Tp& __lhs, const optional<_Tp>& __rhs)
899 { return !__rhs || !(__lhs < *__rhs); }
900
901 // [X.Y.11]
902 template<typename _Tp>
903 inline void
904 swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs)
905 noexcept(noexcept(__lhs.swap(__rhs)))
906 { __lhs.swap(__rhs); }
907
908 template<typename _Tp>
909 constexpr optional<decay_t<_Tp>>
910 make_optional(_Tp&& __t)
911 { return optional<decay_t<_Tp>> { std::forward<_Tp>(__t) }; }
912
913 /// @} relates experimental::optional
914 /// @} group optional
915} // namespace fundamentals_v1
916} // namespace experimental
917
918 // [X.Y.12]
919 /// std::hash partial specialization for experimental::optional
920 /// @relates experimental::optional
921 template<typename _Tp>
922 struct hash<experimental::optional<_Tp>>
923 {
924 using result_type = size_t;
925 using argument_type = experimental::optional<_Tp>;
926
927 size_t
928 operator()(const experimental::optional<_Tp>& __t) const
929 noexcept(noexcept(hash<_Tp> {}(*__t)))
930 {
931 // We pick an arbitrary hash for disengaged optionals which hopefully
932 // usual values of _Tp won't typically hash to.
933 constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333);
934 return __t ? hash<_Tp> {}(*__t) : __magic_disengaged_hash;
935 }
936 };
937
938_GLIBCXX_END_NAMESPACE_VERSION
939} // namespace std
940
941#endif // C++14
942
943#endif // _GLIBCXX_EXPERIMENTAL_OPTIONAL
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