1// Pair implementation -*- C++ -*-
2
3// Copyright (C) 2001-2024 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/*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation. Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose. It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996,1997
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation. Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose. It is provided "as is" without express or implied warranty.
49 */
50
51/** @file bits/stl_pair.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{utility}
54 */
55
56#ifndef _STL_PAIR_H
57#define _STL_PAIR_H 1
58
59#if __cplusplus >= 201103L
60# include <type_traits> // for std::__decay_and_strip
61# include <bits/move.h> // for std::move / std::forward, and std::swap
62# include <bits/utility.h> // for std::tuple_element, std::tuple_size
63#endif
64#if __cplusplus >= 202002L
65# include <compare>
66#endif
67
68namespace std _GLIBCXX_VISIBILITY(default)
69{
70_GLIBCXX_BEGIN_NAMESPACE_VERSION
71
72 /**
73 * @addtogroup utilities
74 * @{
75 */
76
77#if __cplusplus >= 201103L
78 /// Tag type for piecewise construction of std::pair objects.
79 struct piecewise_construct_t { explicit piecewise_construct_t() = default; };
80
81 /// Tag for piecewise construction of std::pair objects.
82 _GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct =
83 piecewise_construct_t();
84
85 /// @cond undocumented
86
87 // Forward declarations.
88 template<typename _T1, typename _T2>
89 struct pair;
90
91 template<typename...>
92 class tuple;
93
94 // Declarations of std::array and its std::get overloads, so that
95 // std::tuple_cat can use them if <tuple> is included before <array>.
96 // We also declare the other std::get overloads here so that they're
97 // visible to the P2165R4 tuple-like constructors of pair and tuple.
98 template<typename _Tp, size_t _Nm>
99 struct array;
100
101 template<size_t...>
102 struct _Index_tuple;
103
104 template<size_t _Int, class _Tp1, class _Tp2>
105 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
106 get(pair<_Tp1, _Tp2>& __in) noexcept;
107
108 template<size_t _Int, class _Tp1, class _Tp2>
109 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
110 get(pair<_Tp1, _Tp2>&& __in) noexcept;
111
112 template<size_t _Int, class _Tp1, class _Tp2>
113 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
114 get(const pair<_Tp1, _Tp2>& __in) noexcept;
115
116 template<size_t _Int, class _Tp1, class _Tp2>
117 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
118 get(const pair<_Tp1, _Tp2>&& __in) noexcept;
119
120 template<size_t __i, typename... _Elements>
121 constexpr __tuple_element_t<__i, tuple<_Elements...>>&
122 get(tuple<_Elements...>& __t) noexcept;
123
124 template<size_t __i, typename... _Elements>
125 constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
126 get(const tuple<_Elements...>& __t) noexcept;
127
128 template<size_t __i, typename... _Elements>
129 constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
130 get(tuple<_Elements...>&& __t) noexcept;
131
132 template<size_t __i, typename... _Elements>
133 constexpr const __tuple_element_t<__i, tuple<_Elements...>>&&
134 get(const tuple<_Elements...>&& __t) noexcept;
135
136 template<size_t _Int, typename _Tp, size_t _Nm>
137 constexpr _Tp&
138 get(array<_Tp, _Nm>&) noexcept;
139
140 template<size_t _Int, typename _Tp, size_t _Nm>
141 constexpr _Tp&&
142 get(array<_Tp, _Nm>&&) noexcept;
143
144 template<size_t _Int, typename _Tp, size_t _Nm>
145 constexpr const _Tp&
146 get(const array<_Tp, _Nm>&) noexcept;
147
148 template<size_t _Int, typename _Tp, size_t _Nm>
149 constexpr const _Tp&&
150 get(const array<_Tp, _Nm>&&) noexcept;
151
152#if ! __cpp_lib_concepts
153 // Concept utility functions, reused in conditionally-explicit
154 // constructors.
155 // See PR 70437, don't look at is_constructible or
156 // is_convertible if the types are the same to
157 // avoid querying those properties for incomplete types.
158 template <bool, typename _T1, typename _T2>
159 struct _PCC
160 {
161 template <typename _U1, typename _U2>
162 static constexpr bool _ConstructiblePair()
163 {
164 return __and_<is_constructible<_T1, const _U1&>,
165 is_constructible<_T2, const _U2&>>::value;
166 }
167
168 template <typename _U1, typename _U2>
169 static constexpr bool _ImplicitlyConvertiblePair()
170 {
171 return __and_<is_convertible<const _U1&, _T1>,
172 is_convertible<const _U2&, _T2>>::value;
173 }
174
175 template <typename _U1, typename _U2>
176 static constexpr bool _MoveConstructiblePair()
177 {
178 return __and_<is_constructible<_T1, _U1&&>,
179 is_constructible<_T2, _U2&&>>::value;
180 }
181
182 template <typename _U1, typename _U2>
183 static constexpr bool _ImplicitlyMoveConvertiblePair()
184 {
185 return __and_<is_convertible<_U1&&, _T1>,
186 is_convertible<_U2&&, _T2>>::value;
187 }
188 };
189
190 template <typename _T1, typename _T2>
191 struct _PCC<false, _T1, _T2>
192 {
193 template <typename _U1, typename _U2>
194 static constexpr bool _ConstructiblePair()
195 {
196 return false;
197 }
198
199 template <typename _U1, typename _U2>
200 static constexpr bool _ImplicitlyConvertiblePair()
201 {
202 return false;
203 }
204
205 template <typename _U1, typename _U2>
206 static constexpr bool _MoveConstructiblePair()
207 {
208 return false;
209 }
210
211 template <typename _U1, typename _U2>
212 static constexpr bool _ImplicitlyMoveConvertiblePair()
213 {
214 return false;
215 }
216 };
217#endif // lib concepts
218#endif // C++11
219
220#if __glibcxx_tuple_like // >= C++23
221 template<typename _Tp>
222 inline constexpr bool __is_tuple_v = false;
223
224 template<typename... _Ts>
225 inline constexpr bool __is_tuple_v<tuple<_Ts...>> = true;
226
227 // TODO: Reuse __is_tuple_like from <type_traits>?
228 template<typename _Tp>
229 inline constexpr bool __is_tuple_like_v = false;
230
231 template<typename... _Elements>
232 inline constexpr bool __is_tuple_like_v<tuple<_Elements...>> = true;
233
234 template<typename _T1, typename _T2>
235 inline constexpr bool __is_tuple_like_v<pair<_T1, _T2>> = true;
236
237 template<typename _Tp, size_t _Nm>
238 inline constexpr bool __is_tuple_like_v<array<_Tp, _Nm>> = true;
239
240 // __is_tuple_like_v<subrange> is defined in <bits/ranges_util.h>.
241
242 template<typename _Tp>
243 concept __tuple_like = __is_tuple_like_v<remove_cvref_t<_Tp>>;
244
245 template<typename _Tp>
246 concept __pair_like = __tuple_like<_Tp> && tuple_size_v<remove_cvref_t<_Tp>> == 2;
247
248 template<typename _Tp, typename _Tuple>
249 concept __eligible_tuple_like
250 = __detail::__different_from<_Tp, _Tuple> && __tuple_like<_Tp>
251 && (tuple_size_v<remove_cvref_t<_Tp>> == tuple_size_v<_Tuple>)
252 && !ranges::__detail::__is_subrange<remove_cvref_t<_Tp>>;
253
254 template<typename _Tp, typename _Pair>
255 concept __eligible_pair_like
256 = __detail::__different_from<_Tp, _Pair> && __pair_like<_Tp>
257 && !ranges::__detail::__is_subrange<remove_cvref_t<_Tp>>;
258#endif // C++23
259
260 template<typename _U1, typename _U2> class __pair_base
261 {
262#if __cplusplus >= 201103L && ! __cpp_lib_concepts
263 template<typename _T1, typename _T2> friend struct pair;
264 __pair_base() = default;
265 ~__pair_base() = default;
266 __pair_base(const __pair_base&) = default;
267 __pair_base& operator=(const __pair_base&) = delete;
268#endif // C++11
269 };
270
271 /// @endcond
272
273 /**
274 * @brief Struct holding two objects of arbitrary type.
275 *
276 * @tparam _T1 Type of first object.
277 * @tparam _T2 Type of second object.
278 *
279 * <https://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
280 *
281 * @headerfile utility
282 */
283 template<typename _T1, typename _T2>
284 struct pair
285 : public __pair_base<_T1, _T2>
286 {
287 typedef _T1 first_type; ///< The type of the `first` member
288 typedef _T2 second_type; ///< The type of the `second` member
289
290 _T1 first; ///< The first member
291 _T2 second; ///< The second member
292
293#if __cplusplus >= 201103L
294 constexpr pair(const pair&) = default; ///< Copy constructor
295 constexpr pair(pair&&) = default; ///< Move constructor
296
297 template<typename... _Args1, typename... _Args2>
298 _GLIBCXX20_CONSTEXPR
299 pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
300
301 /// Swap the first members and then the second members.
302 _GLIBCXX20_CONSTEXPR void
303 swap(pair& __p)
304 noexcept(__and_<__is_nothrow_swappable<_T1>,
305 __is_nothrow_swappable<_T2>>::value)
306 {
307 using std::swap;
308 swap(first, __p.first);
309 swap(second, __p.second);
310 }
311
312#if __glibcxx_ranges_zip // >= C++23
313 // As an extension, we constrain the const swap member function in order
314 // to continue accepting explicit instantiation of pairs whose elements
315 // are not all const swappable. Without this constraint, such an
316 // explicit instantiation would also instantiate the ill-formed body of
317 // this function and yield a hard error. This constraint shouldn't
318 // affect the behavior of valid programs.
319 constexpr void
320 swap(const pair& __p) const
321 noexcept(__and_v<__is_nothrow_swappable<const _T1>,
322 __is_nothrow_swappable<const _T2>>)
323 requires is_swappable_v<const _T1> && is_swappable_v<const _T2>
324 {
325 using std::swap;
326 swap(first, __p.first);
327 swap(second, __p.second);
328 }
329#endif // C++23
330
331 private:
332 template<typename... _Args1, size_t... _Indexes1,
333 typename... _Args2, size_t... _Indexes2>
334 _GLIBCXX20_CONSTEXPR
335 pair(tuple<_Args1...>&, tuple<_Args2...>&,
336 _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
337 public:
338
339#if __cpp_lib_concepts
340 // C++20 implementation using concepts, explicit(bool), fully constexpr.
341
342 /// Default constructor
343 constexpr
344 explicit(__not_<__and_<__is_implicitly_default_constructible<_T1>,
345 __is_implicitly_default_constructible<_T2>>>())
346 pair()
347 requires is_default_constructible_v<_T1>
348 && is_default_constructible_v<_T2>
349 : first(), second()
350 { }
351
352 private:
353
354 /// @cond undocumented
355 template<typename _U1, typename _U2>
356 static constexpr bool
357 _S_constructible()
358 {
359 if constexpr (is_constructible_v<_T1, _U1>)
360 return is_constructible_v<_T2, _U2>;
361 return false;
362 }
363
364 template<typename _U1, typename _U2>
365 static constexpr bool
366 _S_nothrow_constructible()
367 {
368 if constexpr (is_nothrow_constructible_v<_T1, _U1>)
369 return is_nothrow_constructible_v<_T2, _U2>;
370 return false;
371 }
372
373 template<typename _U1, typename _U2>
374 static constexpr bool
375 _S_convertible()
376 {
377 if constexpr (is_convertible_v<_U1, _T1>)
378 return is_convertible_v<_U2, _T2>;
379 return false;
380 }
381
382 // True if construction from _U1 and _U2 would create a dangling ref.
383 template<typename _U1, typename _U2>
384 static constexpr bool
385 _S_dangles()
386 {
387#if __has_builtin(__reference_constructs_from_temporary)
388 if constexpr (__reference_constructs_from_temporary(_T1, _U1&&))
389 return true;
390 else
391 return __reference_constructs_from_temporary(_T2, _U2&&);
392#else
393 return false;
394#endif
395 }
396
397#if __glibcxx_tuple_like // >= C++23
398 template<typename _UPair>
399 static constexpr bool
400 _S_constructible_from_pair_like()
401 {
402 return _S_constructible<decltype(std::get<0>(std::declval<_UPair>())),
403 decltype(std::get<1>(std::declval<_UPair>()))>();
404 }
405
406 template<typename _UPair>
407 static constexpr bool
408 _S_convertible_from_pair_like()
409 {
410 return _S_convertible<decltype(std::get<0>(std::declval<_UPair>())),
411 decltype(std::get<1>(std::declval<_UPair>()))>();
412 }
413
414 template<typename _UPair>
415 static constexpr bool
416 _S_dangles_from_pair_like()
417 {
418 return _S_dangles<decltype(std::get<0>(std::declval<_UPair>())),
419 decltype(std::get<1>(std::declval<_UPair>()))>();
420 }
421#endif // C++23
422 /// @endcond
423
424 public:
425
426 /// Constructor accepting lvalues of `first_type` and `second_type`
427 constexpr explicit(!_S_convertible<const _T1&, const _T2&>())
428 pair(const _T1& __x, const _T2& __y)
429 noexcept(_S_nothrow_constructible<const _T1&, const _T2&>())
430 requires (_S_constructible<const _T1&, const _T2&>())
431 : first(__x), second(__y)
432 { }
433
434 /// Constructor accepting two values of arbitrary types
435#if __cplusplus > 202002L
436 template<typename _U1 = _T1, typename _U2 = _T2>
437#else
438 template<typename _U1, typename _U2>
439#endif
440 requires (_S_constructible<_U1, _U2>()) && (!_S_dangles<_U1, _U2>())
441 constexpr explicit(!_S_convertible<_U1, _U2>())
442 pair(_U1&& __x, _U2&& __y)
443 noexcept(_S_nothrow_constructible<_U1, _U2>())
444 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y))
445 { }
446
447#if __cplusplus > 202002L
448 template<typename _U1 = _T1, typename _U2 = _T2>
449#else
450 template<typename _U1, typename _U2>
451#endif
452 requires (_S_constructible<_U1, _U2>()) && (_S_dangles<_U1, _U2>())
453 constexpr explicit(!_S_convertible<_U1, _U2>())
454 pair(_U1&&, _U2&&) = delete;
455
456 /// Converting constructor from a const `pair<U1, U2>` lvalue
457 template<typename _U1, typename _U2>
458 requires (_S_constructible<const _U1&, const _U2&>())
459 && (!_S_dangles<_U1, _U2>())
460 constexpr explicit(!_S_convertible<const _U1&, const _U2&>())
461 pair(const pair<_U1, _U2>& __p)
462 noexcept(_S_nothrow_constructible<const _U1&, const _U2&>())
463 : first(__p.first), second(__p.second)
464 { }
465
466 template<typename _U1, typename _U2>
467 requires (_S_constructible<const _U1&, const _U2&>())
468 && (_S_dangles<const _U1&, const _U2&>())
469 constexpr explicit(!_S_convertible<const _U1&, const _U2&>())
470 pair(const pair<_U1, _U2>&) = delete;
471
472 /// Converting constructor from a non-const `pair<U1, U2>` rvalue
473 template<typename _U1, typename _U2>
474 requires (_S_constructible<_U1, _U2>()) && (!_S_dangles<_U1, _U2>())
475 constexpr explicit(!_S_convertible<_U1, _U2>())
476 pair(pair<_U1, _U2>&& __p)
477 noexcept(_S_nothrow_constructible<_U1, _U2>())
478 : first(std::forward<_U1>(__p.first)),
479 second(std::forward<_U2>(__p.second))
480 { }
481
482 template<typename _U1, typename _U2>
483 requires (_S_constructible<_U1, _U2>()) && (_S_dangles<_U1, _U2>())
484 constexpr explicit(!_S_convertible<_U1, _U2>())
485 pair(pair<_U1, _U2>&&) = delete;
486
487#if __glibcxx_ranges_zip // >= C++23
488 /// Converting constructor from a non-const `pair<U1, U2>` lvalue
489 template<typename _U1, typename _U2>
490 requires (_S_constructible<_U1&, _U2&>()) && (!_S_dangles<_U1&, _U2&>())
491 constexpr explicit(!_S_convertible<_U1&, _U2&>())
492 pair(pair<_U1, _U2>& __p)
493 noexcept(_S_nothrow_constructible<_U1&, _U2&>())
494 : first(__p.first), second(__p.second)
495 { }
496
497 template<typename _U1, typename _U2>
498 requires (_S_constructible<_U1&, _U2&>()) && (_S_dangles<_U1&, _U2&>())
499 constexpr explicit(!_S_convertible<_U1&, _U2&>())
500 pair(pair<_U1, _U2>&) = delete;
501
502 /// Converting constructor from a const `pair<U1, U2>` rvalue
503 template<typename _U1, typename _U2>
504 requires (_S_constructible<const _U1, const _U2>())
505 && (!_S_dangles<const _U1, const _U2>())
506 constexpr explicit(!_S_convertible<const _U1, const _U2>())
507 pair(const pair<_U1, _U2>&& __p)
508 noexcept(_S_nothrow_constructible<const _U1, const _U2>())
509 : first(std::forward<const _U1>(__p.first)),
510 second(std::forward<const _U2>(__p.second))
511 { }
512
513 template<typename _U1, typename _U2>
514 requires (_S_constructible<const _U1, const _U2>())
515 && (_S_dangles<const _U1, const _U2>())
516 constexpr explicit(!_S_convertible<const _U1, const _U2>())
517 pair(const pair<_U1, _U2>&&) = delete;
518#endif // C++23
519
520#if __glibcxx_tuple_like // >= C++23
521 template<__eligible_pair_like<pair> _UPair>
522 requires (_S_constructible_from_pair_like<_UPair>())
523 && (!_S_dangles_from_pair_like<_UPair>())
524 constexpr explicit(!_S_convertible_from_pair_like<_UPair>())
525 pair(_UPair&& __p)
526 : first(std::get<0>(std::forward<_UPair>(__p))),
527 second(std::get<1>(std::forward<_UPair>(__p)))
528 { }
529
530 template<__eligible_pair_like<pair> _UPair>
531 requires (_S_constructible_from_pair_like<_UPair>())
532 && (_S_dangles_from_pair_like<_UPair>())
533 constexpr explicit(!_S_convertible_from_pair_like<_UPair>())
534 pair(_UPair&&) = delete;
535#endif // C++23
536
537 private:
538 /// @cond undocumented
539 template<typename _U1, typename _U2>
540 static constexpr bool
541 _S_assignable()
542 {
543 if constexpr (is_assignable_v<_T1&, _U1>)
544 return is_assignable_v<_T2&, _U2>;
545 return false;
546 }
547
548 template<typename _U1, typename _U2>
549 static constexpr bool
550 _S_const_assignable()
551 {
552 if constexpr (is_assignable_v<const _T1&, _U1>)
553 return is_assignable_v<const _T2&, _U2>;
554 return false;
555 }
556
557 template<typename _U1, typename _U2>
558 static constexpr bool
559 _S_nothrow_assignable()
560 {
561 if constexpr (is_nothrow_assignable_v<_T1&, _U1>)
562 return is_nothrow_assignable_v<_T2&, _U2>;
563 return false;
564 }
565
566#if __glibcxx_tuple_like // >= C++23
567 template<typename _UPair>
568 static constexpr bool
569 _S_assignable_from_tuple_like()
570 {
571 return _S_assignable<decltype(std::get<0>(std::declval<_UPair>())),
572 decltype(std::get<1>(std::declval<_UPair>()))>();
573 }
574
575 template<typename _UPair>
576 static constexpr bool
577 _S_const_assignable_from_tuple_like()
578 {
579 return _S_const_assignable<decltype(std::get<0>(std::declval<_UPair>())),
580 decltype(std::get<1>(std::declval<_UPair>()))>();
581 }
582#endif // C++23
583 /// @endcond
584
585 public:
586
587 pair& operator=(const pair&) = delete;
588
589 /// Copy assignment operator
590 constexpr pair&
591 operator=(const pair& __p)
592 noexcept(_S_nothrow_assignable<const _T1&, const _T2&>())
593 requires (_S_assignable<const _T1&, const _T2&>())
594 {
595 first = __p.first;
596 second = __p.second;
597 return *this;
598 }
599
600 /// Move assignment operator
601 constexpr pair&
602 operator=(pair&& __p)
603 noexcept(_S_nothrow_assignable<_T1, _T2>())
604 requires (_S_assignable<_T1, _T2>())
605 {
606 first = std::forward<first_type>(__p.first);
607 second = std::forward<second_type>(__p.second);
608 return *this;
609 }
610
611 /// Converting assignment from a const `pair<U1, U2>` lvalue
612 template<typename _U1, typename _U2>
613 constexpr pair&
614 operator=(const pair<_U1, _U2>& __p)
615 noexcept(_S_nothrow_assignable<const _U1&, const _U2&>())
616 requires (_S_assignable<const _U1&, const _U2&>())
617 {
618 first = __p.first;
619 second = __p.second;
620 return *this;
621 }
622
623 /// Converting assignment from a non-const `pair<U1, U2>` rvalue
624 template<typename _U1, typename _U2>
625 constexpr pair&
626 operator=(pair<_U1, _U2>&& __p)
627 noexcept(_S_nothrow_assignable<_U1, _U2>())
628 requires (_S_assignable<_U1, _U2>())
629 {
630 first = std::forward<_U1>(__p.first);
631 second = std::forward<_U2>(__p.second);
632 return *this;
633 }
634
635#if __glibcxx_ranges_zip // >= C++23
636 /// Copy assignment operator (const)
637 constexpr const pair&
638 operator=(const pair& __p) const
639 requires (_S_const_assignable<const first_type&, const second_type&>())
640 {
641 first = __p.first;
642 second = __p.second;
643 return *this;
644 }
645
646 /// Move assignment operator (const)
647 constexpr const pair&
648 operator=(pair&& __p) const
649 requires (_S_const_assignable<first_type, second_type>())
650 {
651 first = std::forward<first_type>(__p.first);
652 second = std::forward<second_type>(__p.second);
653 return *this;
654 }
655
656 /// Converting assignment from a const `pair<U1, U2>` lvalue
657 template<typename _U1, typename _U2>
658 constexpr const pair&
659 operator=(const pair<_U1, _U2>& __p) const
660 requires (_S_const_assignable<const _U1&, const _U2&>())
661 {
662 first = __p.first;
663 second = __p.second;
664 return *this;
665 }
666
667 /// Converting assignment from a non-const `pair<U1, U2>` rvalue
668 template<typename _U1, typename _U2>
669 constexpr const pair&
670 operator=(pair<_U1, _U2>&& __p) const
671 requires (_S_const_assignable<_U1, _U2>())
672 {
673 first = std::forward<_U1>(__p.first);
674 second = std::forward<_U2>(__p.second);
675 return *this;
676 }
677#endif // C++23
678
679#if __glibcxx_tuple_like // >= C++23
680 template<__eligible_pair_like<pair> _UPair>
681 requires (_S_assignable_from_tuple_like<_UPair>())
682 constexpr pair&
683 operator=(_UPair&& __p)
684 {
685 first = std::get<0>(std::forward<_UPair>(__p));
686 second = std::get<1>(std::forward<_UPair>(__p));
687 return *this;
688 }
689
690 template<__eligible_pair_like<pair> _UPair>
691 requires (_S_const_assignable_from_tuple_like<_UPair>())
692 constexpr const pair&
693 operator=(_UPair&& __p) const
694 {
695 first = std::get<0>(std::forward<_UPair>(__p));
696 second = std::get<1>(std::forward<_UPair>(__p));
697 return *this;
698 }
699#endif // C++23
700
701#else // !__cpp_lib_concepts
702 // C++11/14/17 implementation using enable_if, partially constexpr.
703
704 /// @cond undocumented
705 // Error if construction from _U1 and _U2 would create a dangling ref.
706#if __has_builtin(__reference_constructs_from_temporary) \
707 && defined _GLIBCXX_DEBUG
708# define __glibcxx_no_dangling_refs(_U1, _U2) \
709 static_assert(!__reference_constructs_from_temporary(_T1, _U1) \
710 && !__reference_constructs_from_temporary(_T2, _U2), \
711 "std::pair constructor creates a dangling reference")
712#else
713# define __glibcxx_no_dangling_refs(_U1, _U2)
714#endif
715 /// @endcond
716
717 /** The default constructor creates @c first and @c second using their
718 * respective default constructors. */
719 template <typename _U1 = _T1,
720 typename _U2 = _T2,
721 typename enable_if<__and_<
722 __is_implicitly_default_constructible<_U1>,
723 __is_implicitly_default_constructible<_U2>>
724 ::value, bool>::type = true>
725 constexpr pair()
726 : first(), second() { }
727
728 template <typename _U1 = _T1,
729 typename _U2 = _T2,
730 typename enable_if<__and_<
731 is_default_constructible<_U1>,
732 is_default_constructible<_U2>,
733 __not_<
734 __and_<__is_implicitly_default_constructible<_U1>,
735 __is_implicitly_default_constructible<_U2>>>>
736 ::value, bool>::type = false>
737 explicit constexpr pair()
738 : first(), second() { }
739
740 // Shortcut for constraining the templates that don't take pairs.
741 /// @cond undocumented
742 using _PCCP = _PCC<true, _T1, _T2>;
743 /// @endcond
744
745 /// Construct from two const lvalues, allowing implicit conversions.
746 template<typename _U1 = _T1, typename _U2=_T2, typename
747 enable_if<_PCCP::template
748 _ConstructiblePair<_U1, _U2>()
749 && _PCCP::template
750 _ImplicitlyConvertiblePair<_U1, _U2>(),
751 bool>::type=true>
752 constexpr pair(const _T1& __a, const _T2& __b)
753 : first(__a), second(__b) { }
754
755 /// Construct from two const lvalues, disallowing implicit conversions.
756 template<typename _U1 = _T1, typename _U2=_T2, typename
757 enable_if<_PCCP::template
758 _ConstructiblePair<_U1, _U2>()
759 && !_PCCP::template
760 _ImplicitlyConvertiblePair<_U1, _U2>(),
761 bool>::type=false>
762 explicit constexpr pair(const _T1& __a, const _T2& __b)
763 : first(__a), second(__b) { }
764
765 // Shortcut for constraining the templates that take pairs.
766 /// @cond undocumented
767 template <typename _U1, typename _U2>
768 using _PCCFP = _PCC<!is_same<_T1, _U1>::value
769 || !is_same<_T2, _U2>::value,
770 _T1, _T2>;
771 /// @endcond
772
773 template<typename _U1, typename _U2, typename
774 enable_if<_PCCFP<_U1, _U2>::template
775 _ConstructiblePair<_U1, _U2>()
776 && _PCCFP<_U1, _U2>::template
777 _ImplicitlyConvertiblePair<_U1, _U2>(),
778 bool>::type=true>
779 constexpr pair(const pair<_U1, _U2>& __p)
780 : first(__p.first), second(__p.second)
781 { __glibcxx_no_dangling_refs(const _U1&, const _U2&); }
782
783 template<typename _U1, typename _U2, typename
784 enable_if<_PCCFP<_U1, _U2>::template
785 _ConstructiblePair<_U1, _U2>()
786 && !_PCCFP<_U1, _U2>::template
787 _ImplicitlyConvertiblePair<_U1, _U2>(),
788 bool>::type=false>
789 explicit constexpr pair(const pair<_U1, _U2>& __p)
790 : first(__p.first), second(__p.second)
791 { __glibcxx_no_dangling_refs(const _U1&, const _U2&); }
792
793#if _GLIBCXX_USE_DEPRECATED
794#if defined(__DEPRECATED)
795# define _GLIBCXX_DEPRECATED_PAIR_CTOR \
796 __attribute__ ((__deprecated__ ("use 'nullptr' instead of '0' to " \
797 "initialize std::pair of move-only " \
798 "type and pointer")))
799#else
800# define _GLIBCXX_DEPRECATED_PAIR_CTOR
801#endif
802
803 private:
804 /// @cond undocumented
805
806 // A type which can be constructed from literal zero, but not nullptr
807 struct __zero_as_null_pointer_constant
808 {
809 __zero_as_null_pointer_constant(int __zero_as_null_pointer_constant::*)
810 { }
811 template<typename _Tp,
812 typename = __enable_if_t<is_null_pointer<_Tp>::value>>
813 __zero_as_null_pointer_constant(_Tp) = delete;
814 };
815 /// @endcond
816 public:
817
818 // Deprecated extensions to DR 811.
819 // These allow construction from an rvalue and a literal zero,
820 // in cases where the standard says the zero should be deduced as int
821 template<typename _U1,
822 __enable_if_t<__and_<__not_<is_reference<_U1>>,
823 is_pointer<_T2>,
824 is_constructible<_T1, _U1>,
825 __not_<is_constructible<_T1, const _U1&>>,
826 is_convertible<_U1, _T1>>::value,
827 bool> = true>
828 _GLIBCXX_DEPRECATED_PAIR_CTOR
829 constexpr
830 pair(_U1&& __x, __zero_as_null_pointer_constant, ...)
831 : first(std::forward<_U1>(__x)), second(nullptr)
832 { __glibcxx_no_dangling_refs(_U1&&, std::nullptr_t); }
833
834 template<typename _U1,
835 __enable_if_t<__and_<__not_<is_reference<_U1>>,
836 is_pointer<_T2>,
837 is_constructible<_T1, _U1>,
838 __not_<is_constructible<_T1, const _U1&>>,
839 __not_<is_convertible<_U1, _T1>>>::value,
840 bool> = false>
841 _GLIBCXX_DEPRECATED_PAIR_CTOR
842 explicit constexpr
843 pair(_U1&& __x, __zero_as_null_pointer_constant, ...)
844 : first(std::forward<_U1>(__x)), second(nullptr)
845 { __glibcxx_no_dangling_refs(_U1&&, std::nullptr_t); }
846
847 template<typename _U2,
848 __enable_if_t<__and_<is_pointer<_T1>,
849 __not_<is_reference<_U2>>,
850 is_constructible<_T2, _U2>,
851 __not_<is_constructible<_T2, const _U2&>>,
852 is_convertible<_U2, _T2>>::value,
853 bool> = true>
854 _GLIBCXX_DEPRECATED_PAIR_CTOR
855 constexpr
856 pair(__zero_as_null_pointer_constant, _U2&& __y, ...)
857 : first(nullptr), second(std::forward<_U2>(__y))
858 { __glibcxx_no_dangling_refs(std::nullptr_t, _U2&&); }
859
860 template<typename _U2,
861 __enable_if_t<__and_<is_pointer<_T1>,
862 __not_<is_reference<_U2>>,
863 is_constructible<_T2, _U2>,
864 __not_<is_constructible<_T2, const _U2&>>,
865 __not_<is_convertible<_U2, _T2>>>::value,
866 bool> = false>
867 _GLIBCXX_DEPRECATED_PAIR_CTOR
868 explicit constexpr
869 pair(__zero_as_null_pointer_constant, _U2&& __y, ...)
870 : first(nullptr), second(std::forward<_U2>(__y))
871 { __glibcxx_no_dangling_refs(std::nullptr_t, _U2&&); }
872#undef _GLIBCXX_DEPRECATED_PAIR_CTOR
873#endif
874
875 template<typename _U1, typename _U2, typename
876 enable_if<_PCCP::template
877 _MoveConstructiblePair<_U1, _U2>()
878 && _PCCP::template
879 _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
880 bool>::type=true>
881 constexpr pair(_U1&& __x, _U2&& __y)
882 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y))
883 { __glibcxx_no_dangling_refs(_U1&&, _U2&&); }
884
885 template<typename _U1, typename _U2, typename
886 enable_if<_PCCP::template
887 _MoveConstructiblePair<_U1, _U2>()
888 && !_PCCP::template
889 _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
890 bool>::type=false>
891 explicit constexpr pair(_U1&& __x, _U2&& __y)
892 : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y))
893 { __glibcxx_no_dangling_refs(_U1&&, _U2&&); }
894
895
896 template<typename _U1, typename _U2, typename
897 enable_if<_PCCFP<_U1, _U2>::template
898 _MoveConstructiblePair<_U1, _U2>()
899 && _PCCFP<_U1, _U2>::template
900 _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
901 bool>::type=true>
902 constexpr pair(pair<_U1, _U2>&& __p)
903 : first(std::forward<_U1>(__p.first)),
904 second(std::forward<_U2>(__p.second))
905 { __glibcxx_no_dangling_refs(_U1&&, _U2&&); }
906
907 template<typename _U1, typename _U2, typename
908 enable_if<_PCCFP<_U1, _U2>::template
909 _MoveConstructiblePair<_U1, _U2>()
910 && !_PCCFP<_U1, _U2>::template
911 _ImplicitlyMoveConvertiblePair<_U1, _U2>(),
912 bool>::type=false>
913 explicit constexpr pair(pair<_U1, _U2>&& __p)
914 : first(std::forward<_U1>(__p.first)),
915 second(std::forward<_U2>(__p.second))
916 { __glibcxx_no_dangling_refs(_U1&&, _U2&&); }
917
918#undef __glibcxx_no_dangling_refs
919
920 pair&
921 operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
922 is_copy_assignable<_T2>>::value,
923 const pair&, const __nonesuch&> __p)
924 {
925 first = __p.first;
926 second = __p.second;
927 return *this;
928 }
929
930 pair&
931 operator=(__conditional_t<__and_<is_move_assignable<_T1>,
932 is_move_assignable<_T2>>::value,
933 pair&&, __nonesuch&&> __p)
934 noexcept(__and_<is_nothrow_move_assignable<_T1>,
935 is_nothrow_move_assignable<_T2>>::value)
936 {
937 first = std::forward<first_type>(__p.first);
938 second = std::forward<second_type>(__p.second);
939 return *this;
940 }
941
942 template<typename _U1, typename _U2>
943 typename enable_if<__and_<is_assignable<_T1&, const _U1&>,
944 is_assignable<_T2&, const _U2&>>::value,
945 pair&>::type
946 operator=(const pair<_U1, _U2>& __p)
947 {
948 first = __p.first;
949 second = __p.second;
950 return *this;
951 }
952
953 template<typename _U1, typename _U2>
954 typename enable_if<__and_<is_assignable<_T1&, _U1&&>,
955 is_assignable<_T2&, _U2&&>>::value,
956 pair&>::type
957 operator=(pair<_U1, _U2>&& __p)
958 {
959 first = std::forward<_U1>(__p.first);
960 second = std::forward<_U2>(__p.second);
961 return *this;
962 }
963#endif // lib concepts
964#else
965 // C++03 implementation
966
967 // _GLIBCXX_RESOLVE_LIB_DEFECTS
968 // 265. std::pair::pair() effects overly restrictive
969 /** The default constructor creates @c first and @c second using their
970 * respective default constructors. */
971 pair() : first(), second() { }
972
973 /// Two objects may be passed to a `pair` constructor to be copied.
974 pair(const _T1& __a, const _T2& __b)
975 : first(__a), second(__b) { }
976
977 /// Templated constructor to convert from other pairs.
978 template<typename _U1, typename _U2>
979 pair(const pair<_U1, _U2>& __p)
980 : first(__p.first), second(__p.second)
981 {
982#if __has_builtin(__reference_constructs_from_temporary)
983#pragma GCC diagnostic push
984#pragma GCC diagnostic ignored "-Wunused-local-typedefs"
985 typedef int _DanglingCheck1[
986 __reference_constructs_from_temporary(_T1, const _U1&) ? -1 : 1
987 ];
988 typedef int _DanglingCheck2[
989 __reference_constructs_from_temporary(_T2, const _U2&) ? -1 : 1
990 ];
991#pragma GCC diagnostic pop
992#endif
993 }
994#endif // C++11
995 };
996
997 /// @relates pair @{
998
999#if __cpp_deduction_guides >= 201606
1000 template<typename _T1, typename _T2> pair(_T1, _T2) -> pair<_T1, _T2>;
1001#endif
1002
1003#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
1004 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1005 // 3865. Sorting a range of pairs
1006
1007 /// Two pairs are equal iff their members are equal.
1008 template<typename _T1, typename _T2, typename _U1, typename _U2>
1009 inline _GLIBCXX_CONSTEXPR bool
1010 operator==(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y)
1011 { return __x.first == __y.first && __x.second == __y.second; }
1012
1013 /** Defines a lexicographical order for pairs.
1014 *
1015 * For two pairs of comparable types, `P` is ordered before `Q` if
1016 * `P.first` is less than `Q.first`, or if `P.first` and `Q.first`
1017 * are equivalent (neither is less than the other) and `P.second` is
1018 * less than `Q.second`.
1019 */
1020 template<typename _T1, typename _T2, typename _U1, typename _U2>
1021 constexpr common_comparison_category_t<__detail::__synth3way_t<_T1, _U1>,
1022 __detail::__synth3way_t<_T2, _U2>>
1023 operator<=>(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y)
1024 {
1025 if (auto __c = __detail::__synth3way(__x.first, __y.first); __c != 0)
1026 return __c;
1027 return __detail::__synth3way(__x.second, __y.second);
1028 }
1029#else
1030 /// Two pairs of the same type are equal iff their members are equal.
1031 template<typename _T1, typename _T2>
1032 inline _GLIBCXX_CONSTEXPR bool
1033 operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1034 { return __x.first == __y.first && __x.second == __y.second; }
1035
1036 /** Defines a lexicographical order for pairs.
1037 *
1038 * For two pairs of the same type, `P` is ordered before `Q` if
1039 * `P.first` is less than `Q.first`, or if `P.first` and `Q.first`
1040 * are equivalent (neither is less than the other) and `P.second` is less
1041 * than `Q.second`.
1042 */
1043 template<typename _T1, typename _T2>
1044 inline _GLIBCXX_CONSTEXPR bool
1045 operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1046 { return __x.first < __y.first
1047 || (!(__y.first < __x.first) && __x.second < __y.second); }
1048
1049 /// Uses @c operator== to find the result.
1050 template<typename _T1, typename _T2>
1051 inline _GLIBCXX_CONSTEXPR bool
1052 operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1053 { return !(__x == __y); }
1054
1055 /// Uses @c operator< to find the result.
1056 template<typename _T1, typename _T2>
1057 inline _GLIBCXX_CONSTEXPR bool
1058 operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1059 { return __y < __x; }
1060
1061 /// Uses @c operator< to find the result.
1062 template<typename _T1, typename _T2>
1063 inline _GLIBCXX_CONSTEXPR bool
1064 operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1065 { return !(__y < __x); }
1066
1067 /// Uses @c operator< to find the result.
1068 template<typename _T1, typename _T2>
1069 inline _GLIBCXX_CONSTEXPR bool
1070 operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1071 { return !(__x < __y); }
1072#endif // !(three_way_comparison && concepts)
1073
1074#if __cplusplus >= 201103L
1075 /** Swap overload for pairs. Calls std::pair::swap().
1076 *
1077 * @note This std::swap overload is not declared in C++03 mode,
1078 * which has performance implications, e.g. see https://gcc.gnu.org/PR38466
1079 */
1080 template<typename _T1, typename _T2>
1081 _GLIBCXX20_CONSTEXPR inline
1082#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1083 // Constrained free swap overload, see p0185r1
1084 typename enable_if<__and_<__is_swappable<_T1>,
1085 __is_swappable<_T2>>::value>::type
1086#else
1087 void
1088#endif
1089 swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
1090 noexcept(noexcept(__x.swap(__y)))
1091 { __x.swap(__y); }
1092
1093#if __glibcxx_ranges_zip // >= C++23
1094 template<typename _T1, typename _T2>
1095 requires is_swappable_v<const _T1> && is_swappable_v<const _T2>
1096 constexpr void
1097 swap(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
1098 noexcept(noexcept(__x.swap(__y)))
1099 { __x.swap(__y); }
1100#endif // C++23
1101
1102#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1103 template<typename _T1, typename _T2>
1104 typename enable_if<!__and_<__is_swappable<_T1>,
1105 __is_swappable<_T2>>::value>::type
1106 swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete;
1107#endif
1108#endif // __cplusplus >= 201103L
1109
1110 /// @} relates pair
1111
1112 /**
1113 * @brief A convenience wrapper for creating a pair from two objects.
1114 * @param __x The first object.
1115 * @param __y The second object.
1116 * @return A newly-constructed pair<> object of the appropriate type.
1117 *
1118 * The C++98 standard says the objects are passed by reference-to-const,
1119 * but C++03 says they are passed by value (this was LWG issue #181).
1120 *
1121 * Since C++11 they have been passed by forwarding reference and then
1122 * forwarded to the new members of the pair. To create a pair with a
1123 * member of reference type, pass a `reference_wrapper` to this function.
1124 */
1125 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1126 // 181. make_pair() unintended behavior
1127#if __cplusplus >= 201103L
1128 // NB: DR 706.
1129 template<typename _T1, typename _T2>
1130 constexpr pair<typename __decay_and_strip<_T1>::__type,
1131 typename __decay_and_strip<_T2>::__type>
1132 make_pair(_T1&& __x, _T2&& __y)
1133 {
1134 typedef typename __decay_and_strip<_T1>::__type __ds_type1;
1135 typedef typename __decay_and_strip<_T2>::__type __ds_type2;
1136 typedef pair<__ds_type1, __ds_type2> __pair_type;
1137 return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
1138 }
1139#else
1140 template<typename _T1, typename _T2>
1141 inline pair<_T1, _T2>
1142 make_pair(_T1 __x, _T2 __y)
1143 { return pair<_T1, _T2>(__x, __y); }
1144#endif
1145
1146 /// @}
1147
1148#if __cplusplus >= 201103L
1149 // Various functions which give std::pair a tuple-like interface.
1150
1151 /// @cond undocumented
1152 template<typename _T1, typename _T2>
1153 struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
1154 { };
1155 /// @endcond
1156
1157 /// Partial specialization for std::pair
1158 template<class _Tp1, class _Tp2>
1159 struct tuple_size<pair<_Tp1, _Tp2>>
1160 : public integral_constant<size_t, 2> { };
1161
1162 /// Partial specialization for std::pair
1163 template<class _Tp1, class _Tp2>
1164 struct tuple_element<0, pair<_Tp1, _Tp2>>
1165 { typedef _Tp1 type; };
1166
1167 /// Partial specialization for std::pair
1168 template<class _Tp1, class _Tp2>
1169 struct tuple_element<1, pair<_Tp1, _Tp2>>
1170 { typedef _Tp2 type; };
1171
1172 // Forward declare the partial specialization for std::tuple
1173 // to work around modules bug PR c++/113814.
1174 template<size_t __i, typename... _Types>
1175 struct tuple_element<__i, tuple<_Types...>>;
1176
1177#if __cplusplus >= 201703L
1178 template<typename _Tp1, typename _Tp2>
1179 inline constexpr size_t tuple_size_v<pair<_Tp1, _Tp2>> = 2;
1180
1181 template<typename _Tp1, typename _Tp2>
1182 inline constexpr size_t tuple_size_v<const pair<_Tp1, _Tp2>> = 2;
1183
1184 template<typename _Tp>
1185 inline constexpr bool __is_pair = false;
1186
1187 template<typename _Tp, typename _Up>
1188 inline constexpr bool __is_pair<pair<_Tp, _Up>> = true;
1189#endif
1190
1191 /// @cond undocumented
1192 template<size_t _Int>
1193 struct __pair_get;
1194
1195 template<>
1196 struct __pair_get<0>
1197 {
1198 template<typename _Tp1, typename _Tp2>
1199 static constexpr _Tp1&
1200 __get(pair<_Tp1, _Tp2>& __pair) noexcept
1201 { return __pair.first; }
1202
1203 template<typename _Tp1, typename _Tp2>
1204 static constexpr _Tp1&&
1205 __move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
1206 { return std::forward<_Tp1>(__pair.first); }
1207
1208 template<typename _Tp1, typename _Tp2>
1209 static constexpr const _Tp1&
1210 __const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
1211 { return __pair.first; }
1212
1213 template<typename _Tp1, typename _Tp2>
1214 static constexpr const _Tp1&&
1215 __const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
1216 { return std::forward<const _Tp1>(__pair.first); }
1217 };
1218
1219 template<>
1220 struct __pair_get<1>
1221 {
1222 template<typename _Tp1, typename _Tp2>
1223 static constexpr _Tp2&
1224 __get(pair<_Tp1, _Tp2>& __pair) noexcept
1225 { return __pair.second; }
1226
1227 template<typename _Tp1, typename _Tp2>
1228 static constexpr _Tp2&&
1229 __move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
1230 { return std::forward<_Tp2>(__pair.second); }
1231
1232 template<typename _Tp1, typename _Tp2>
1233 static constexpr const _Tp2&
1234 __const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
1235 { return __pair.second; }
1236
1237 template<typename _Tp1, typename _Tp2>
1238 static constexpr const _Tp2&&
1239 __const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
1240 { return std::forward<const _Tp2>(__pair.second); }
1241 };
1242 /// @endcond
1243
1244 /** @{
1245 * std::get overloads for accessing members of std::pair
1246 */
1247
1248 template<size_t _Int, class _Tp1, class _Tp2>
1249 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
1250 get(pair<_Tp1, _Tp2>& __in) noexcept
1251 { return __pair_get<_Int>::__get(__in); }
1252
1253 template<size_t _Int, class _Tp1, class _Tp2>
1254 constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
1255 get(pair<_Tp1, _Tp2>&& __in) noexcept
1256 { return __pair_get<_Int>::__move_get(std::move(__in)); }
1257
1258 template<size_t _Int, class _Tp1, class _Tp2>
1259 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
1260 get(const pair<_Tp1, _Tp2>& __in) noexcept
1261 { return __pair_get<_Int>::__const_get(__in); }
1262
1263 template<size_t _Int, class _Tp1, class _Tp2>
1264 constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
1265 get(const pair<_Tp1, _Tp2>&& __in) noexcept
1266 { return __pair_get<_Int>::__const_move_get(std::move(__in)); }
1267
1268
1269#ifdef __glibcxx_tuples_by_type // C++ >= 14
1270 template <typename _Tp, typename _Up>
1271 constexpr _Tp&
1272 get(pair<_Tp, _Up>& __p) noexcept
1273 { return __p.first; }
1274
1275 template <typename _Tp, typename _Up>
1276 constexpr const _Tp&
1277 get(const pair<_Tp, _Up>& __p) noexcept
1278 { return __p.first; }
1279
1280 template <typename _Tp, typename _Up>
1281 constexpr _Tp&&
1282 get(pair<_Tp, _Up>&& __p) noexcept
1283 { return std::move(__p.first); }
1284
1285 template <typename _Tp, typename _Up>
1286 constexpr const _Tp&&
1287 get(const pair<_Tp, _Up>&& __p) noexcept
1288 { return std::move(__p.first); }
1289
1290 template <typename _Tp, typename _Up>
1291 constexpr _Tp&
1292 get(pair<_Up, _Tp>& __p) noexcept
1293 { return __p.second; }
1294
1295 template <typename _Tp, typename _Up>
1296 constexpr const _Tp&
1297 get(const pair<_Up, _Tp>& __p) noexcept
1298 { return __p.second; }
1299
1300 template <typename _Tp, typename _Up>
1301 constexpr _Tp&&
1302 get(pair<_Up, _Tp>&& __p) noexcept
1303 { return std::move(__p.second); }
1304
1305 template <typename _Tp, typename _Up>
1306 constexpr const _Tp&&
1307 get(const pair<_Up, _Tp>&& __p) noexcept
1308 { return std::move(__p.second); }
1309#endif // __glibcxx_tuples_by_type
1310
1311
1312#if __glibcxx_ranges_zip // >= C++23
1313 template<typename _T1, typename _T2, typename _U1, typename _U2,
1314 template<typename> class _TQual, template<typename> class _UQual>
1315 requires requires { typename pair<common_reference_t<_TQual<_T1>, _UQual<_U1>>,
1316 common_reference_t<_TQual<_T2>, _UQual<_U2>>>; }
1317 struct basic_common_reference<pair<_T1, _T2>, pair<_U1, _U2>, _TQual, _UQual>
1318 {
1319 using type = pair<common_reference_t<_TQual<_T1>, _UQual<_U1>>,
1320 common_reference_t<_TQual<_T2>, _UQual<_U2>>>;
1321 };
1322
1323 template<typename _T1, typename _T2, typename _U1, typename _U2>
1324 requires requires { typename pair<common_type_t<_T1, _U1>, common_type_t<_T2, _U2>>; }
1325 struct common_type<pair<_T1, _T2>, pair<_U1, _U2>>
1326 { using type = pair<common_type_t<_T1, _U1>, common_type_t<_T2, _U2>>; };
1327#endif // C++23
1328
1329 /// @}
1330#endif // C++11
1331
1332_GLIBCXX_END_NAMESPACE_VERSION
1333} // namespace std
1334
1335#endif /* _STL_PAIR_H */
1336