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optional
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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 include/optional
26  * This is a Standard C++ Library header.
27  */
28 
29 #ifndef _GLIBCXX_OPTIONAL
30 #define _GLIBCXX_OPTIONAL 1
31 
32 #pragma GCC system_header
33 
34 #if __cplusplus >= 201703L
35 
36 #include <utility>
37 #include <type_traits>
38 #include <exception>
39 #include <new>
40 #include <initializer_list>
41 #include <bits/enable_special_members.h>
42 #include <bits/exception_defines.h>
43 #include <bits/functional_hash.h>
44 #include <bits/stl_construct.h> // _Construct
45 #if __cplusplus > 201703L
46 # include <compare>
47 #endif
48 
49 namespace std _GLIBCXX_VISIBILITY(default)
50 {
51 _GLIBCXX_BEGIN_NAMESPACE_VERSION
52 
53  /**
54  * @addtogroup utilities
55  * @{
56  */
57 
58 #if __cplusplus == 201703L
59 # define __cpp_lib_optional 201606L
60 #else
61 # define __cpp_lib_optional 202106L
62 #endif
63 
64  template<typename _Tp>
65  class optional;
66 
67  /// Tag type to disengage optional objects.
68  struct nullopt_t
69  {
70  // Do not user-declare default constructor at all for
71  // optional_value = {} syntax to work.
72  // nullopt_t() = delete;
73 
74  // Used for constructing nullopt.
75  enum class _Construct { _Token };
76 
77  // Must be constexpr for nullopt_t to be literal.
78  explicit constexpr nullopt_t(_Construct) noexcept { }
79  };
80 
81  /// Tag to disengage optional objects.
82  inline constexpr nullopt_t nullopt { nullopt_t::_Construct::_Token };
83 
84  /**
85  * @brief Exception class thrown when a disengaged optional object is
86  * dereferenced.
87  * @ingroup exceptions
88  */
89  class bad_optional_access : public exception
90  {
91  public:
92  bad_optional_access() = default;
93  virtual ~bad_optional_access() = default;
94 
95  const char* what() const noexcept override
96  { return "bad optional access"; }
97  };
98 
99  // XXX Does not belong here.
100  [[__noreturn__]] inline void
101  __throw_bad_optional_access()
102  { _GLIBCXX_THROW_OR_ABORT(bad_optional_access()); }
103 
104  // This class template manages construction/destruction of
105  // the contained value for a std::optional.
106  template <typename _Tp>
107  struct _Optional_payload_base
108  {
109  using _Stored_type = remove_const_t<_Tp>;
110 
111  _Optional_payload_base() = default;
112  ~_Optional_payload_base() = default;
113 
114  template<typename... _Args>
115  constexpr
116  _Optional_payload_base(in_place_t __tag, _Args&&... __args)
117  : _M_payload(__tag, std::forward<_Args>(__args)...),
118  _M_engaged(true)
119  { }
120 
121  template<typename _Up, typename... _Args>
122  constexpr
123  _Optional_payload_base(std::initializer_list<_Up> __il,
124  _Args&&... __args)
125  : _M_payload(__il, std::forward<_Args>(__args)...),
126  _M_engaged(true)
127  { }
128 
129  // Constructor used by _Optional_base copy constructor when the
130  // contained value is not trivially copy constructible.
131  constexpr
132  _Optional_payload_base(bool __engaged,
133  const _Optional_payload_base& __other)
134  {
135  if (__other._M_engaged)
136  this->_M_construct(__other._M_get());
137  }
138 
139  // Constructor used by _Optional_base move constructor when the
140  // contained value is not trivially move constructible.
141  constexpr
142  _Optional_payload_base(bool __engaged,
143  _Optional_payload_base&& __other)
144  {
145  if (__other._M_engaged)
146  this->_M_construct(std::move(__other._M_get()));
147  }
148 
149  // Copy constructor is only used to when the contained value is
150  // trivially copy constructible.
151  _Optional_payload_base(const _Optional_payload_base&) = default;
152 
153  // Move constructor is only used to when the contained value is
154  // trivially copy constructible.
155  _Optional_payload_base(_Optional_payload_base&&) = default;
156 
157  _Optional_payload_base&
158  operator=(const _Optional_payload_base&) = default;
159 
160  _Optional_payload_base&
161  operator=(_Optional_payload_base&&) = default;
162 
163  // used to perform non-trivial copy assignment.
164  constexpr void
165  _M_copy_assign(const _Optional_payload_base& __other)
166  {
167  if (this->_M_engaged && __other._M_engaged)
168  this->_M_get() = __other._M_get();
169  else
170  {
171  if (__other._M_engaged)
172  this->_M_construct(__other._M_get());
173  else
174  this->_M_reset();
175  }
176  }
177 
178  // used to perform non-trivial move assignment.
179  constexpr void
180  _M_move_assign(_Optional_payload_base&& __other)
181  noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
182  is_nothrow_move_assignable<_Tp>>)
183  {
184  if (this->_M_engaged && __other._M_engaged)
185  this->_M_get() = std::move(__other._M_get());
186  else
187  {
188  if (__other._M_engaged)
189  this->_M_construct(std::move(__other._M_get()));
190  else
191  this->_M_reset();
192  }
193  }
194 
195  struct _Empty_byte { };
196 
197  template<typename _Up, bool = is_trivially_destructible_v<_Up>>
198  union _Storage
199  {
200  constexpr _Storage() noexcept : _M_empty() { }
201 
202  template<typename... _Args>
203  constexpr
204  _Storage(in_place_t, _Args&&... __args)
205  : _M_value(std::forward<_Args>(__args)...)
206  { }
207 
208  template<typename _Vp, typename... _Args>
209  constexpr
210  _Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
211  : _M_value(__il, std::forward<_Args>(__args)...)
212  { }
213 
214  _Empty_byte _M_empty;
215  _Up _M_value;
216  };
217 
218  template<typename _Up>
219  union _Storage<_Up, false>
220  {
221  constexpr _Storage() noexcept : _M_empty() { }
222 
223  template<typename... _Args>
224  constexpr
225  _Storage(in_place_t, _Args&&... __args)
226  : _M_value(std::forward<_Args>(__args)...)
227  { }
228 
229  template<typename _Vp, typename... _Args>
230  constexpr
231  _Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
232  : _M_value(__il, std::forward<_Args>(__args)...)
233  { }
234 
235  // User-provided destructor is needed when _Up has non-trivial dtor.
236  _GLIBCXX20_CONSTEXPR ~_Storage() { }
237 
238  _Empty_byte _M_empty;
239  _Up _M_value;
240  };
241 
242  _Storage<_Stored_type> _M_payload;
243 
244  bool _M_engaged = false;
245 
246  template<typename... _Args>
247  constexpr void
248  _M_construct(_Args&&... __args)
249  noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
250  {
251  std::_Construct(std::__addressof(this->_M_payload._M_value),
252  std::forward<_Args>(__args)...);
253  this->_M_engaged = true;
254  }
255 
256  constexpr void
257  _M_destroy() noexcept
258  {
259  _M_engaged = false;
260  _M_payload._M_value.~_Stored_type();
261  }
262 
263  // The _M_get() operations have _M_engaged as a precondition.
264  // They exist to access the contained value with the appropriate
265  // const-qualification, because _M_payload has had the const removed.
266 
267  constexpr _Tp&
268  _M_get() noexcept
269  { return this->_M_payload._M_value; }
270 
271  constexpr const _Tp&
272  _M_get() const noexcept
273  { return this->_M_payload._M_value; }
274 
275  // _M_reset is a 'safe' operation with no precondition.
276  constexpr void
277  _M_reset() noexcept
278  {
279  if (this->_M_engaged)
280  _M_destroy();
281  }
282  };
283 
284  // Class template that manages the payload for optionals.
285  template <typename _Tp,
286  bool /*_HasTrivialDestructor*/ =
287  is_trivially_destructible_v<_Tp>,
288  bool /*_HasTrivialCopy */ =
289  is_trivially_copy_assignable_v<_Tp>
290  && is_trivially_copy_constructible_v<_Tp>,
291  bool /*_HasTrivialMove */ =
292  is_trivially_move_assignable_v<_Tp>
293  && is_trivially_move_constructible_v<_Tp>>
294  struct _Optional_payload;
295 
296  // Payload for potentially-constexpr optionals (trivial copy/move/destroy).
297  template <typename _Tp>
298  struct _Optional_payload<_Tp, true, true, true>
299  : _Optional_payload_base<_Tp>
300  {
301  using _Optional_payload_base<_Tp>::_Optional_payload_base;
302 
303  _Optional_payload() = default;
304  };
305 
306  // Payload for optionals with non-trivial copy construction/assignment.
307  template <typename _Tp>
308  struct _Optional_payload<_Tp, true, false, true>
309  : _Optional_payload_base<_Tp>
310  {
311  using _Optional_payload_base<_Tp>::_Optional_payload_base;
312 
313  _Optional_payload() = default;
314  ~_Optional_payload() = default;
315  _Optional_payload(const _Optional_payload&) = default;
316  _Optional_payload(_Optional_payload&&) = default;
317  _Optional_payload& operator=(_Optional_payload&&) = default;
318 
319  // Non-trivial copy assignment.
320  constexpr
321  _Optional_payload&
322  operator=(const _Optional_payload& __other)
323  {
324  this->_M_copy_assign(__other);
325  return *this;
326  }
327  };
328 
329  // Payload for optionals with non-trivial move construction/assignment.
330  template <typename _Tp>
331  struct _Optional_payload<_Tp, true, true, false>
332  : _Optional_payload_base<_Tp>
333  {
334  using _Optional_payload_base<_Tp>::_Optional_payload_base;
335 
336  _Optional_payload() = default;
337  ~_Optional_payload() = default;
338  _Optional_payload(const _Optional_payload&) = default;
339  _Optional_payload(_Optional_payload&&) = default;
340  _Optional_payload& operator=(const _Optional_payload&) = default;
341 
342  // Non-trivial move assignment.
343  constexpr
344  _Optional_payload&
345  operator=(_Optional_payload&& __other)
346  noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
347  is_nothrow_move_assignable<_Tp>>)
348  {
349  this->_M_move_assign(std::move(__other));
350  return *this;
351  }
352  };
353 
354  // Payload for optionals with non-trivial copy and move assignment.
355  template <typename _Tp>
356  struct _Optional_payload<_Tp, true, false, false>
357  : _Optional_payload_base<_Tp>
358  {
359  using _Optional_payload_base<_Tp>::_Optional_payload_base;
360 
361  _Optional_payload() = default;
362  ~_Optional_payload() = default;
363  _Optional_payload(const _Optional_payload&) = default;
364  _Optional_payload(_Optional_payload&&) = default;
365 
366  // Non-trivial copy assignment.
367  constexpr
368  _Optional_payload&
369  operator=(const _Optional_payload& __other)
370  {
371  this->_M_copy_assign(__other);
372  return *this;
373  }
374 
375  // Non-trivial move assignment.
376  constexpr
377  _Optional_payload&
378  operator=(_Optional_payload&& __other)
379  noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
380  is_nothrow_move_assignable<_Tp>>)
381  {
382  this->_M_move_assign(std::move(__other));
383  return *this;
384  }
385  };
386 
387  // Payload for optionals with non-trivial destructors.
388  template <typename _Tp, bool _Copy, bool _Move>
389  struct _Optional_payload<_Tp, false, _Copy, _Move>
390  : _Optional_payload<_Tp, true, false, false>
391  {
392  // Base class implements all the constructors and assignment operators:
393  using _Optional_payload<_Tp, true, false, false>::_Optional_payload;
394  _Optional_payload() = default;
395  _Optional_payload(const _Optional_payload&) = default;
396  _Optional_payload(_Optional_payload&&) = default;
397  _Optional_payload& operator=(const _Optional_payload&) = default;
398  _Optional_payload& operator=(_Optional_payload&&) = default;
399 
400  // Destructor needs to destroy the contained value:
401  _GLIBCXX20_CONSTEXPR ~_Optional_payload() { this->_M_reset(); }
402  };
403 
404  // Common base class for _Optional_base<T> to avoid repeating these
405  // member functions in each specialization.
406  template<typename _Tp, typename _Dp>
407  class _Optional_base_impl
408  {
409  protected:
410  using _Stored_type = remove_const_t<_Tp>;
411 
412  // The _M_construct operation has !_M_engaged as a precondition
413  // while _M_destruct has _M_engaged as a precondition.
414  template<typename... _Args>
415  constexpr void
416  _M_construct(_Args&&... __args)
417  noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
418  {
419  static_cast<_Dp*>(this)->_M_payload._M_construct(
420  std::forward<_Args>(__args)...);
421  }
422 
423  constexpr void
424  _M_destruct() noexcept
425  { static_cast<_Dp*>(this)->_M_payload._M_destroy(); }
426 
427  // _M_reset is a 'safe' operation with no precondition.
428  constexpr void
429  _M_reset() noexcept
430  { static_cast<_Dp*>(this)->_M_payload._M_reset(); }
431 
432  constexpr bool _M_is_engaged() const noexcept
433  { return static_cast<const _Dp*>(this)->_M_payload._M_engaged; }
434 
435  // The _M_get operations have _M_engaged as a precondition.
436  constexpr _Tp&
437  _M_get() noexcept
438  {
439  __glibcxx_assert(this->_M_is_engaged());
440  return static_cast<_Dp*>(this)->_M_payload._M_get();
441  }
442 
443  constexpr const _Tp&
444  _M_get() const noexcept
445  {
446  __glibcxx_assert(this->_M_is_engaged());
447  return static_cast<const _Dp*>(this)->_M_payload._M_get();
448  }
449  };
450 
451  /**
452  * @brief Class template that provides copy/move constructors of optional.
453  *
454  * Such a separate base class template is necessary in order to
455  * conditionally make copy/move constructors trivial.
456  *
457  * When the contained value is trivially copy/move constructible,
458  * the copy/move constructors of _Optional_base will invoke the
459  * trivial copy/move constructor of _Optional_payload. Otherwise,
460  * they will invoke _Optional_payload(bool, const _Optional_payload&)
461  * or _Optional_payload(bool, _Optional_payload&&) to initialize
462  * the contained value, if copying/moving an engaged optional.
463  *
464  * Whether the other special members are trivial is determined by the
465  * _Optional_payload<_Tp> specialization used for the _M_payload member.
466  *
467  * @see optional, _Enable_special_members
468  */
469  template<typename _Tp,
470  bool = is_trivially_copy_constructible_v<_Tp>,
471  bool = is_trivially_move_constructible_v<_Tp>>
472  struct _Optional_base
473  : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
474  {
475  // Constructors for disengaged optionals.
476  constexpr _Optional_base() = default;
477 
478  // Constructors for engaged optionals.
479  template<typename... _Args,
480  enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
481  constexpr explicit
482  _Optional_base(in_place_t, _Args&&... __args)
483  : _M_payload(in_place, std::forward<_Args>(__args)...)
484  { }
485 
486  template<typename _Up, typename... _Args,
487  enable_if_t<is_constructible_v<_Tp,
488  initializer_list<_Up>&,
489  _Args...>, bool> = false>
490  constexpr explicit
491  _Optional_base(in_place_t,
492  initializer_list<_Up> __il,
493  _Args&&... __args)
494  : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
495  { }
496 
497  // Copy and move constructors.
498  constexpr
499  _Optional_base(const _Optional_base& __other)
500  : _M_payload(__other._M_payload._M_engaged, __other._M_payload)
501  { }
502 
503  constexpr
504  _Optional_base(_Optional_base&& __other)
505  noexcept(is_nothrow_move_constructible_v<_Tp>)
506  : _M_payload(__other._M_payload._M_engaged,
507  std::move(__other._M_payload))
508  { }
509 
510  // Assignment operators.
511  _Optional_base& operator=(const _Optional_base&) = default;
512  _Optional_base& operator=(_Optional_base&&) = default;
513 
514  _Optional_payload<_Tp> _M_payload;
515  };
516 
517  template<typename _Tp>
518  struct _Optional_base<_Tp, false, true>
519  : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
520  {
521  // Constructors for disengaged optionals.
522  constexpr _Optional_base() = default;
523 
524  // Constructors for engaged optionals.
525  template<typename... _Args,
526  enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
527  constexpr explicit
528  _Optional_base(in_place_t, _Args&&... __args)
529  : _M_payload(in_place, std::forward<_Args>(__args)...)
530  { }
531 
532  template<typename _Up, typename... _Args,
533  enable_if_t<is_constructible_v<_Tp,
534  initializer_list<_Up>&,
535  _Args...>, bool> = false>
536  constexpr explicit
537  _Optional_base(in_place_t,
538  initializer_list<_Up> __il,
539  _Args... __args)
540  : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
541  { }
542 
543  // Copy and move constructors.
544  constexpr _Optional_base(const _Optional_base& __other)
545  : _M_payload(__other._M_payload._M_engaged, __other._M_payload)
546  { }
547 
548  constexpr _Optional_base(_Optional_base&& __other) = default;
549 
550  // Assignment operators.
551  _Optional_base& operator=(const _Optional_base&) = default;
552  _Optional_base& operator=(_Optional_base&&) = default;
553 
554  _Optional_payload<_Tp> _M_payload;
555  };
556 
557  template<typename _Tp>
558  struct _Optional_base<_Tp, true, false>
559  : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
560  {
561  // Constructors for disengaged optionals.
562  constexpr _Optional_base() = default;
563 
564  // Constructors for engaged optionals.
565  template<typename... _Args,
566  enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
567  constexpr explicit
568  _Optional_base(in_place_t, _Args&&... __args)
569  : _M_payload(in_place, std::forward<_Args>(__args)...)
570  { }
571 
572  template<typename _Up, typename... _Args,
573  enable_if_t<is_constructible_v<_Tp,
574  initializer_list<_Up>&,
575  _Args...>, bool> = false>
576  constexpr explicit
577  _Optional_base(in_place_t,
578  initializer_list<_Up> __il,
579  _Args&&... __args)
580  : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
581  { }
582 
583  // Copy and move constructors.
584  constexpr _Optional_base(const _Optional_base& __other) = default;
585 
586  constexpr
587  _Optional_base(_Optional_base&& __other)
588  noexcept(is_nothrow_move_constructible_v<_Tp>)
589  : _M_payload(__other._M_payload._M_engaged,
590  std::move(__other._M_payload))
591  { }
592 
593  // Assignment operators.
594  _Optional_base& operator=(const _Optional_base&) = default;
595  _Optional_base& operator=(_Optional_base&&) = default;
596 
597  _Optional_payload<_Tp> _M_payload;
598  };
599 
600  template<typename _Tp>
601  struct _Optional_base<_Tp, true, true>
602  : _Optional_base_impl<_Tp, _Optional_base<_Tp>>
603  {
604  // Constructors for disengaged optionals.
605  constexpr _Optional_base() = default;
606 
607  // Constructors for engaged optionals.
608  template<typename... _Args,
609  enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
610  constexpr explicit
611  _Optional_base(in_place_t, _Args&&... __args)
612  : _M_payload(in_place, std::forward<_Args>(__args)...)
613  { }
614 
615  template<typename _Up, typename... _Args,
616  enable_if_t<is_constructible_v<_Tp,
617  initializer_list<_Up>&,
618  _Args...>, bool> = false>
619  constexpr explicit
620  _Optional_base(in_place_t,
621  initializer_list<_Up> __il,
622  _Args&&... __args)
623  : _M_payload(in_place, __il, std::forward<_Args>(__args)...)
624  { }
625 
626  // Copy and move constructors.
627  constexpr _Optional_base(const _Optional_base& __other) = default;
628  constexpr _Optional_base(_Optional_base&& __other) = default;
629 
630  // Assignment operators.
631  _Optional_base& operator=(const _Optional_base&) = default;
632  _Optional_base& operator=(_Optional_base&&) = default;
633 
634  _Optional_payload<_Tp> _M_payload;
635  };
636 
637  template<typename _Tp>
638  class optional;
639 
640  template<typename _Tp, typename _Up>
641  using __converts_from_optional =
642  __or_<is_constructible<_Tp, const optional<_Up>&>,
643  is_constructible<_Tp, optional<_Up>&>,
644  is_constructible<_Tp, const optional<_Up>&&>,
645  is_constructible<_Tp, optional<_Up>&&>,
646  is_convertible<const optional<_Up>&, _Tp>,
647  is_convertible<optional<_Up>&, _Tp>,
648  is_convertible<const optional<_Up>&&, _Tp>,
649  is_convertible<optional<_Up>&&, _Tp>>;
650 
651  template<typename _Tp, typename _Up>
652  using __assigns_from_optional =
653  __or_<is_assignable<_Tp&, const optional<_Up>&>,
654  is_assignable<_Tp&, optional<_Up>&>,
655  is_assignable<_Tp&, const optional<_Up>&&>,
656  is_assignable<_Tp&, optional<_Up>&&>>;
657 
658  /**
659  * @brief Class template for optional values.
660  */
661  template<typename _Tp>
662  class optional
663  : private _Optional_base<_Tp>,
664  private _Enable_copy_move<
665  // Copy constructor.
666  is_copy_constructible_v<_Tp>,
667  // Copy assignment.
668  __and_v<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>,
669  // Move constructor.
670  is_move_constructible_v<_Tp>,
671  // Move assignment.
672  __and_v<is_move_constructible<_Tp>, is_move_assignable<_Tp>>,
673  // Unique tag type.
674  optional<_Tp>>
675  {
676  static_assert(!is_same_v<remove_cv_t<_Tp>, nullopt_t>);
677  static_assert(!is_same_v<remove_cv_t<_Tp>, in_place_t>);
678  static_assert(!is_reference_v<_Tp>);
679 
680  private:
681  using _Base = _Optional_base<_Tp>;
682 
683  // SFINAE helpers
684  template<typename _Up>
685  using __not_self = __not_<is_same<optional, __remove_cvref_t<_Up>>>;
686  template<typename _Up>
687  using __not_tag = __not_<is_same<in_place_t, __remove_cvref_t<_Up>>>;
688  template<typename... _Cond>
689  using _Requires = enable_if_t<__and_v<_Cond...>, bool>;
690 
691  public:
692  using value_type = _Tp;
693 
694  constexpr optional() noexcept { }
695 
696  constexpr optional(nullopt_t) noexcept { }
697 
698  // Converting constructors for engaged optionals.
699  template<typename _Up = _Tp,
700  _Requires<__not_self<_Up>, __not_tag<_Up>,
701  is_constructible<_Tp, _Up>,
702  is_convertible<_Up, _Tp>> = true>
703  constexpr
704  optional(_Up&& __t)
705  noexcept(is_nothrow_constructible_v<_Tp, _Up>)
706  : _Base(std::in_place, std::forward<_Up>(__t)) { }
707 
708  template<typename _Up = _Tp,
709  _Requires<__not_self<_Up>, __not_tag<_Up>,
710  is_constructible<_Tp, _Up>,
711  __not_<is_convertible<_Up, _Tp>>> = false>
712  explicit constexpr
713  optional(_Up&& __t)
714  noexcept(is_nothrow_constructible_v<_Tp, _Up>)
715  : _Base(std::in_place, std::forward<_Up>(__t)) { }
716 
717  template<typename _Up,
718  _Requires<__not_<is_same<_Tp, _Up>>,
719  is_constructible<_Tp, const _Up&>,
720  is_convertible<const _Up&, _Tp>,
721  __not_<__converts_from_optional<_Tp, _Up>>> = true>
722  constexpr
723  optional(const optional<_Up>& __t)
724  noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
725  {
726  if (__t)
727  emplace(*__t);
728  }
729 
730  template<typename _Up,
731  _Requires<__not_<is_same<_Tp, _Up>>,
732  is_constructible<_Tp, const _Up&>,
733  __not_<is_convertible<const _Up&, _Tp>>,
734  __not_<__converts_from_optional<_Tp, _Up>>> = false>
735  explicit constexpr
736  optional(const optional<_Up>& __t)
737  noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
738  {
739  if (__t)
740  emplace(*__t);
741  }
742 
743  template<typename _Up,
744  _Requires<__not_<is_same<_Tp, _Up>>,
745  is_constructible<_Tp, _Up>,
746  is_convertible<_Up, _Tp>,
747  __not_<__converts_from_optional<_Tp, _Up>>> = true>
748  constexpr
749  optional(optional<_Up>&& __t)
750  noexcept(is_nothrow_constructible_v<_Tp, _Up>)
751  {
752  if (__t)
753  emplace(std::move(*__t));
754  }
755 
756  template<typename _Up,
757  _Requires<__not_<is_same<_Tp, _Up>>,
758  is_constructible<_Tp, _Up>,
759  __not_<is_convertible<_Up, _Tp>>,
760  __not_<__converts_from_optional<_Tp, _Up>>> = false>
761  explicit constexpr
762  optional(optional<_Up>&& __t)
763  noexcept(is_nothrow_constructible_v<_Tp, _Up>)
764  {
765  if (__t)
766  emplace(std::move(*__t));
767  }
768 
769  template<typename... _Args,
770  _Requires<is_constructible<_Tp, _Args...>> = false>
771  explicit constexpr
772  optional(in_place_t, _Args&&... __args)
773  noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
774  : _Base(std::in_place, std::forward<_Args>(__args)...) { }
775 
776  template<typename _Up, typename... _Args,
777  _Requires<is_constructible<_Tp,
778  initializer_list<_Up>&,
779  _Args...>> = false>
780  explicit constexpr
781  optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
782  noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
783  _Args...>)
784  : _Base(std::in_place, __il, std::forward<_Args>(__args)...) { }
785 
786 
787  // Assignment operators.
788  _GLIBCXX20_CONSTEXPR optional&
789  operator=(nullopt_t) noexcept
790  {
791  this->_M_reset();
792  return *this;
793  }
794 
795  template<typename _Up = _Tp>
796  _GLIBCXX20_CONSTEXPR
797  enable_if_t<__and_v<__not_self<_Up>,
798  __not_<__and_<is_scalar<_Tp>,
799  is_same<_Tp, decay_t<_Up>>>>,
800  is_constructible<_Tp, _Up>,
801  is_assignable<_Tp&, _Up>>,
802  optional&>
803  operator=(_Up&& __u)
804  noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
805  is_nothrow_assignable<_Tp&, _Up>>)
806  {
807  if (this->_M_is_engaged())
808  this->_M_get() = std::forward<_Up>(__u);
809  else
810  this->_M_construct(std::forward<_Up>(__u));
811 
812  return *this;
813  }
814 
815  template<typename _Up>
816  _GLIBCXX20_CONSTEXPR
817  enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
818  is_constructible<_Tp, const _Up&>,
819  is_assignable<_Tp&, const _Up&>,
820  __not_<__converts_from_optional<_Tp, _Up>>,
821  __not_<__assigns_from_optional<_Tp, _Up>>>,
822  optional&>
823  operator=(const optional<_Up>& __u)
824  noexcept(__and_v<is_nothrow_constructible<_Tp, const _Up&>,
825  is_nothrow_assignable<_Tp&, const _Up&>>)
826  {
827  if (__u)
828  {
829  if (this->_M_is_engaged())
830  this->_M_get() = *__u;
831  else
832  this->_M_construct(*__u);
833  }
834  else
835  {
836  this->_M_reset();
837  }
838  return *this;
839  }
840 
841  template<typename _Up>
842  _GLIBCXX20_CONSTEXPR
843  enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
844  is_constructible<_Tp, _Up>,
845  is_assignable<_Tp&, _Up>,
846  __not_<__converts_from_optional<_Tp, _Up>>,
847  __not_<__assigns_from_optional<_Tp, _Up>>>,
848  optional&>
849  operator=(optional<_Up>&& __u)
850  noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
851  is_nothrow_assignable<_Tp&, _Up>>)
852  {
853  if (__u)
854  {
855  if (this->_M_is_engaged())
856  this->_M_get() = std::move(*__u);
857  else
858  this->_M_construct(std::move(*__u));
859  }
860  else
861  {
862  this->_M_reset();
863  }
864 
865  return *this;
866  }
867 
868  template<typename... _Args>
869  _GLIBCXX20_CONSTEXPR
870  enable_if_t<is_constructible_v<_Tp, _Args...>, _Tp&>
871  emplace(_Args&&... __args)
872  noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
873  {
874  this->_M_reset();
875  this->_M_construct(std::forward<_Args>(__args)...);
876  return this->_M_get();
877  }
878 
879  template<typename _Up, typename... _Args>
880  _GLIBCXX20_CONSTEXPR
881  enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
882  _Tp&>
883  emplace(initializer_list<_Up> __il, _Args&&... __args)
884  noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
885  _Args...>)
886  {
887  this->_M_reset();
888  this->_M_construct(__il, std::forward<_Args>(__args)...);
889  return this->_M_get();
890  }
891 
892  // Destructor is implicit, implemented in _Optional_base.
893 
894  // Swap.
895  _GLIBCXX20_CONSTEXPR void
896  swap(optional& __other)
897  noexcept(is_nothrow_move_constructible_v<_Tp>
898  && is_nothrow_swappable_v<_Tp>)
899  {
900  using std::swap;
901 
902  if (this->_M_is_engaged() && __other._M_is_engaged())
903  swap(this->_M_get(), __other._M_get());
904  else if (this->_M_is_engaged())
905  {
906  __other._M_construct(std::move(this->_M_get()));
907  this->_M_destruct();
908  }
909  else if (__other._M_is_engaged())
910  {
911  this->_M_construct(std::move(__other._M_get()));
912  __other._M_destruct();
913  }
914  }
915 
916  // Observers.
917  constexpr const _Tp*
918  operator->() const noexcept
919  { return std::__addressof(this->_M_get()); }
920 
921  constexpr _Tp*
922  operator->() noexcept
923  { return std::__addressof(this->_M_get()); }
924 
925  constexpr const _Tp&
926  operator*() const& noexcept
927  { return this->_M_get(); }
928 
929  constexpr _Tp&
930  operator*()& noexcept
931  { return this->_M_get(); }
932 
933  constexpr _Tp&&
934  operator*()&& noexcept
935  { return std::move(this->_M_get()); }
936 
937  constexpr const _Tp&&
938  operator*() const&& noexcept
939  { return std::move(this->_M_get()); }
940 
941  constexpr explicit operator bool() const noexcept
942  { return this->_M_is_engaged(); }
943 
944  constexpr bool has_value() const noexcept
945  { return this->_M_is_engaged(); }
946 
947  constexpr const _Tp&
948  value() const&
949  {
950  if (this->_M_is_engaged())
951  return this->_M_get();
952  __throw_bad_optional_access();
953  }
954 
955  constexpr _Tp&
956  value()&
957  {
958  if (this->_M_is_engaged())
959  return this->_M_get();
960  __throw_bad_optional_access();
961  }
962 
963  constexpr _Tp&&
964  value()&&
965  {
966  if (this->_M_is_engaged())
967  return std::move(this->_M_get());
968  __throw_bad_optional_access();
969  }
970 
971  constexpr const _Tp&&
972  value() const&&
973  {
974  if (this->_M_is_engaged())
975  return std::move(this->_M_get());
976  __throw_bad_optional_access();
977  }
978 
979  template<typename _Up>
980  constexpr _Tp
981  value_or(_Up&& __u) const&
982  {
983  static_assert(is_copy_constructible_v<_Tp>);
984  static_assert(is_convertible_v<_Up&&, _Tp>);
985 
986  if (this->_M_is_engaged())
987  return this->_M_get();
988  else
989  return static_cast<_Tp>(std::forward<_Up>(__u));
990  }
991 
992  template<typename _Up>
993  constexpr _Tp
994  value_or(_Up&& __u) &&
995  {
996  static_assert(is_move_constructible_v<_Tp>);
997  static_assert(is_convertible_v<_Up&&, _Tp>);
998 
999  if (this->_M_is_engaged())
1000  return std::move(this->_M_get());
1001  else
1002  return static_cast<_Tp>(std::forward<_Up>(__u));
1003  }
1004 
1005  _GLIBCXX20_CONSTEXPR void reset() noexcept { this->_M_reset(); }
1006  };
1007 
1008  template<typename _Tp>
1009  using __optional_relop_t =
1010  enable_if_t<is_convertible<_Tp, bool>::value, bool>;
1011 
1012  template<typename _Tp, typename _Up>
1013  using __optional_eq_t = __optional_relop_t<
1014  decltype(std::declval<const _Tp&>() == std::declval<const _Up&>())
1015  >;
1016 
1017  template<typename _Tp, typename _Up>
1018  using __optional_ne_t = __optional_relop_t<
1019  decltype(std::declval<const _Tp&>() != std::declval<const _Up&>())
1020  >;
1021 
1022  template<typename _Tp, typename _Up>
1023  using __optional_lt_t = __optional_relop_t<
1024  decltype(std::declval<const _Tp&>() < std::declval<const _Up&>())
1025  >;
1026 
1027  template<typename _Tp, typename _Up>
1028  using __optional_gt_t = __optional_relop_t<
1029  decltype(std::declval<const _Tp&>() > std::declval<const _Up&>())
1030  >;
1031 
1032  template<typename _Tp, typename _Up>
1033  using __optional_le_t = __optional_relop_t<
1034  decltype(std::declval<const _Tp&>() <= std::declval<const _Up&>())
1035  >;
1036 
1037  template<typename _Tp, typename _Up>
1038  using __optional_ge_t = __optional_relop_t<
1039  decltype(std::declval<const _Tp&>() >= std::declval<const _Up&>())
1040  >;
1041 
1042  // Comparisons between optional values.
1043  template<typename _Tp, typename _Up>
1044  constexpr auto
1045  operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1046  -> __optional_eq_t<_Tp, _Up>
1047  {
1048  return static_cast<bool>(__lhs) == static_cast<bool>(__rhs)
1049  && (!__lhs || *__lhs == *__rhs);
1050  }
1051 
1052  template<typename _Tp, typename _Up>
1053  constexpr auto
1054  operator!=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1055  -> __optional_ne_t<_Tp, _Up>
1056  {
1057  return static_cast<bool>(__lhs) != static_cast<bool>(__rhs)
1058  || (static_cast<bool>(__lhs) && *__lhs != *__rhs);
1059  }
1060 
1061  template<typename _Tp, typename _Up>
1062  constexpr auto
1063  operator<(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1064  -> __optional_lt_t<_Tp, _Up>
1065  {
1066  return static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs);
1067  }
1068 
1069  template<typename _Tp, typename _Up>
1070  constexpr auto
1071  operator>(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1072  -> __optional_gt_t<_Tp, _Up>
1073  {
1074  return static_cast<bool>(__lhs) && (!__rhs || *__lhs > *__rhs);
1075  }
1076 
1077  template<typename _Tp, typename _Up>
1078  constexpr auto
1079  operator<=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1080  -> __optional_le_t<_Tp, _Up>
1081  {
1082  return !__lhs || (static_cast<bool>(__rhs) && *__lhs <= *__rhs);
1083  }
1084 
1085  template<typename _Tp, typename _Up>
1086  constexpr auto
1087  operator>=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
1088  -> __optional_ge_t<_Tp, _Up>
1089  {
1090  return !__rhs || (static_cast<bool>(__lhs) && *__lhs >= *__rhs);
1091  }
1092 
1093 #ifdef __cpp_lib_three_way_comparison
1094  template<typename _Tp, three_way_comparable_with<_Tp> _Up>
1095  constexpr compare_three_way_result_t<_Tp, _Up>
1096  operator<=>(const optional<_Tp>& __x, const optional<_Up>& __y)
1097  {
1098  return __x && __y ? *__x <=> *__y : bool(__x) <=> bool(__y);
1099  }
1100 #endif
1101 
1102  // Comparisons with nullopt.
1103  template<typename _Tp>
1104  constexpr bool
1105  operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
1106  { return !__lhs; }
1107 
1108 #ifdef __cpp_lib_three_way_comparison
1109  template<typename _Tp>
1110  constexpr strong_ordering
1111  operator<=>(const optional<_Tp>& __x, nullopt_t) noexcept
1112  { return bool(__x) <=> false; }
1113 #else
1114  template<typename _Tp>
1115  constexpr bool
1116  operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
1117  { return !__rhs; }
1118 
1119  template<typename _Tp>
1120  constexpr bool
1121  operator!=(const optional<_Tp>& __lhs, nullopt_t) noexcept
1122  { return static_cast<bool>(__lhs); }
1123 
1124  template<typename _Tp>
1125  constexpr bool
1126  operator!=(nullopt_t, const optional<_Tp>& __rhs) noexcept
1127  { return static_cast<bool>(__rhs); }
1128 
1129  template<typename _Tp>
1130  constexpr bool
1131  operator<(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
1132  { return false; }
1133 
1134  template<typename _Tp>
1135  constexpr bool
1136  operator<(nullopt_t, const optional<_Tp>& __rhs) noexcept
1137  { return static_cast<bool>(__rhs); }
1138 
1139  template<typename _Tp>
1140  constexpr bool
1141  operator>(const optional<_Tp>& __lhs, nullopt_t) noexcept
1142  { return static_cast<bool>(__lhs); }
1143 
1144  template<typename _Tp>
1145  constexpr bool
1146  operator>(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
1147  { return false; }
1148 
1149  template<typename _Tp>
1150  constexpr bool
1151  operator<=(const optional<_Tp>& __lhs, nullopt_t) noexcept
1152  { return !__lhs; }
1153 
1154  template<typename _Tp>
1155  constexpr bool
1156  operator<=(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
1157  { return true; }
1158 
1159  template<typename _Tp>
1160  constexpr bool
1161  operator>=(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
1162  { return true; }
1163 
1164  template<typename _Tp>
1165  constexpr bool
1166  operator>=(nullopt_t, const optional<_Tp>& __rhs) noexcept
1167  { return !__rhs; }
1168 #endif // three-way-comparison
1169 
1170  // Comparisons with value type.
1171  template<typename _Tp, typename _Up>
1172  constexpr auto
1173  operator==(const optional<_Tp>& __lhs, const _Up& __rhs)
1174  -> __optional_eq_t<_Tp, _Up>
1175  { return __lhs && *__lhs == __rhs; }
1176 
1177  template<typename _Tp, typename _Up>
1178  constexpr auto
1179  operator==(const _Up& __lhs, const optional<_Tp>& __rhs)
1180  -> __optional_eq_t<_Up, _Tp>
1181  { return __rhs && __lhs == *__rhs; }
1182 
1183  template<typename _Tp, typename _Up>
1184  constexpr auto
1185  operator!=(const optional<_Tp>& __lhs, const _Up& __rhs)
1186  -> __optional_ne_t<_Tp, _Up>
1187  { return !__lhs || *__lhs != __rhs; }
1188 
1189  template<typename _Tp, typename _Up>
1190  constexpr auto
1191  operator!=(const _Up& __lhs, const optional<_Tp>& __rhs)
1192  -> __optional_ne_t<_Up, _Tp>
1193  { return !__rhs || __lhs != *__rhs; }
1194 
1195  template<typename _Tp, typename _Up>
1196  constexpr auto
1197  operator<(const optional<_Tp>& __lhs, const _Up& __rhs)
1198  -> __optional_lt_t<_Tp, _Up>
1199  { return !__lhs || *__lhs < __rhs; }
1200 
1201  template<typename _Tp, typename _Up>
1202  constexpr auto
1203  operator<(const _Up& __lhs, const optional<_Tp>& __rhs)
1204  -> __optional_lt_t<_Up, _Tp>
1205  { return __rhs && __lhs < *__rhs; }
1206 
1207  template<typename _Tp, typename _Up>
1208  constexpr auto
1209  operator>(const optional<_Tp>& __lhs, const _Up& __rhs)
1210  -> __optional_gt_t<_Tp, _Up>
1211  { return __lhs && *__lhs > __rhs; }
1212 
1213  template<typename _Tp, typename _Up>
1214  constexpr auto
1215  operator>(const _Up& __lhs, const optional<_Tp>& __rhs)
1216  -> __optional_gt_t<_Up, _Tp>
1217  { return !__rhs || __lhs > *__rhs; }
1218 
1219  template<typename _Tp, typename _Up>
1220  constexpr auto
1221  operator<=(const optional<_Tp>& __lhs, const _Up& __rhs)
1222  -> __optional_le_t<_Tp, _Up>
1223  { return !__lhs || *__lhs <= __rhs; }
1224 
1225  template<typename _Tp, typename _Up>
1226  constexpr auto
1227  operator<=(const _Up& __lhs, const optional<_Tp>& __rhs)
1228  -> __optional_le_t<_Up, _Tp>
1229  { return __rhs && __lhs <= *__rhs; }
1230 
1231  template<typename _Tp, typename _Up>
1232  constexpr auto
1233  operator>=(const optional<_Tp>& __lhs, const _Up& __rhs)
1234  -> __optional_ge_t<_Tp, _Up>
1235  { return __lhs && *__lhs >= __rhs; }
1236 
1237  template<typename _Tp, typename _Up>
1238  constexpr auto
1239  operator>=(const _Up& __lhs, const optional<_Tp>& __rhs)
1240  -> __optional_ge_t<_Up, _Tp>
1241  { return !__rhs || __lhs >= *__rhs; }
1242 
1243 #ifdef __cpp_lib_three_way_comparison
1244  template<typename _Tp>
1245  inline constexpr bool __is_optional_v = false;
1246  template<typename _Tp>
1247  inline constexpr bool __is_optional_v<optional<_Tp>> = true;
1248 
1249  template<typename _Tp, typename _Up>
1250  requires (!__is_optional_v<_Up>)
1251  && three_way_comparable_with<_Tp, _Up>
1252  constexpr compare_three_way_result_t<_Tp, _Up>
1253  operator<=>(const optional<_Tp>& __x, const _Up& __v)
1254  { return bool(__x) ? *__x <=> __v : strong_ordering::less; }
1255 #endif
1256 
1257  // Swap and creation functions.
1258 
1259  // _GLIBCXX_RESOLVE_LIB_DEFECTS
1260  // 2748. swappable traits for optionals
1261  template<typename _Tp>
1262  _GLIBCXX20_CONSTEXPR
1263  inline enable_if_t<is_move_constructible_v<_Tp> && is_swappable_v<_Tp>>
1264  swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs)
1265  noexcept(noexcept(__lhs.swap(__rhs)))
1266  { __lhs.swap(__rhs); }
1267 
1268  template<typename _Tp>
1269  enable_if_t<!(is_move_constructible_v<_Tp> && is_swappable_v<_Tp>)>
1270  swap(optional<_Tp>&, optional<_Tp>&) = delete;
1271 
1272  template<typename _Tp>
1273  constexpr
1274  enable_if_t<is_constructible_v<decay_t<_Tp>, _Tp>,
1275  optional<decay_t<_Tp>>>
1276  make_optional(_Tp&& __t)
1277  noexcept(is_nothrow_constructible_v<optional<decay_t<_Tp>>, _Tp>)
1278  { return optional<decay_t<_Tp>>{ std::forward<_Tp>(__t) }; }
1279 
1280  template<typename _Tp, typename... _Args>
1281  constexpr
1282  enable_if_t<is_constructible_v<_Tp, _Args...>,
1283  optional<_Tp>>
1284  make_optional(_Args&&... __args)
1285  noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
1286  { return optional<_Tp>{ in_place, std::forward<_Args>(__args)... }; }
1287 
1288  template<typename _Tp, typename _Up, typename... _Args>
1289  constexpr
1290  enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
1291  optional<_Tp>>
1292  make_optional(initializer_list<_Up> __il, _Args&&... __args)
1293  noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
1294  { return optional<_Tp>{ in_place, __il, std::forward<_Args>(__args)... }; }
1295 
1296  // Hash.
1297 
1298  template<typename _Tp, typename _Up = remove_const_t<_Tp>,
1299  bool = __poison_hash<_Up>::__enable_hash_call>
1300  struct __optional_hash_call_base
1301  {
1302  size_t
1303  operator()(const optional<_Tp>& __t) const
1304  noexcept(noexcept(hash<_Up>{}(*__t)))
1305  {
1306  // We pick an arbitrary hash for disengaged optionals which hopefully
1307  // usual values of _Tp won't typically hash to.
1308  constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333);
1309  return __t ? hash<_Up>{}(*__t) : __magic_disengaged_hash;
1310  }
1311  };
1312 
1313  template<typename _Tp, typename _Up>
1314  struct __optional_hash_call_base<_Tp, _Up, false> {};
1315 
1316  template<typename _Tp>
1317  struct hash<optional<_Tp>>
1318  : private __poison_hash<remove_const_t<_Tp>>,
1319  public __optional_hash_call_base<_Tp>
1320  {
1321  using result_type [[__deprecated__]] = size_t;
1322  using argument_type [[__deprecated__]] = optional<_Tp>;
1323  };
1324 
1325  template<typename _Tp>
1326  struct __is_fast_hash<hash<optional<_Tp>>> : __is_fast_hash<hash<_Tp>>
1327  { };
1328 
1329  /// @}
1330 
1331 #if __cpp_deduction_guides >= 201606
1332  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
1333 #endif
1334 
1335 _GLIBCXX_END_NAMESPACE_VERSION
1336 } // namespace std
1337 
1338 #endif // C++17
1339 
1340 #endif // _GLIBCXX_OPTIONAL