libstdc++
tuple
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1// <tuple> -*- C++ -*-
2
3// Copyright (C) 2007-2020 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/tuple
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_TUPLE
30#define _GLIBCXX_TUPLE 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <utility>
39#include <array>
40#include <bits/uses_allocator.h>
41#include <bits/invoke.h>
42#if __cplusplus > 201703L
43# include <compare>
44# define __cpp_lib_constexpr_tuple 201811L
45#endif
46
47namespace std _GLIBCXX_VISIBILITY(default)
48{
49_GLIBCXX_BEGIN_NAMESPACE_VERSION
50
51 /**
52 * @addtogroup utilities
53 * @{
54 */
55
56 template<typename... _Elements>
57 class tuple;
58
59 template<typename _Tp>
60 struct __is_empty_non_tuple : is_empty<_Tp> { };
61
62 // Using EBO for elements that are tuples causes ambiguous base errors.
63 template<typename _El0, typename... _El>
64 struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
65
66 // Use the Empty Base-class Optimization for empty, non-final types.
67 template<typename _Tp>
68 using __empty_not_final
69 = typename conditional<__is_final(_Tp), false_type,
70 __is_empty_non_tuple<_Tp>>::type;
71
72 template<std::size_t _Idx, typename _Head,
73 bool = __empty_not_final<_Head>::value>
74 struct _Head_base;
75
76 template<std::size_t _Idx, typename _Head>
77 struct _Head_base<_Idx, _Head, true>
78 : public _Head
79 {
80 constexpr _Head_base()
81 : _Head() { }
82
83 constexpr _Head_base(const _Head& __h)
84 : _Head(__h) { }
85
86 constexpr _Head_base(const _Head_base&) = default;
87 constexpr _Head_base(_Head_base&&) = default;
88
89 template<typename _UHead>
90 constexpr _Head_base(_UHead&& __h)
91 : _Head(std::forward<_UHead>(__h)) { }
92
93 _GLIBCXX20_CONSTEXPR
94 _Head_base(allocator_arg_t, __uses_alloc0)
95 : _Head() { }
96
97 template<typename _Alloc>
98 _GLIBCXX20_CONSTEXPR
99 _Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
100 : _Head(allocator_arg, *__a._M_a) { }
101
102 template<typename _Alloc>
103 _GLIBCXX20_CONSTEXPR
104 _Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
105 : _Head(*__a._M_a) { }
106
107 template<typename _UHead>
108 _GLIBCXX20_CONSTEXPR
109 _Head_base(__uses_alloc0, _UHead&& __uhead)
110 : _Head(std::forward<_UHead>(__uhead)) { }
111
112 template<typename _Alloc, typename _UHead>
113 _GLIBCXX20_CONSTEXPR
114 _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
115 : _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }
116
117 template<typename _Alloc, typename _UHead>
118 _GLIBCXX20_CONSTEXPR
119 _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
120 : _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }
121
122 static constexpr _Head&
123 _M_head(_Head_base& __b) noexcept { return __b; }
124
125 static constexpr const _Head&
126 _M_head(const _Head_base& __b) noexcept { return __b; }
127 };
128
129 template<std::size_t _Idx, typename _Head>
130 struct _Head_base<_Idx, _Head, false>
131 {
132 constexpr _Head_base()
133 : _M_head_impl() { }
134
135 constexpr _Head_base(const _Head& __h)
136 : _M_head_impl(__h) { }
137
138 constexpr _Head_base(const _Head_base&) = default;
139 constexpr _Head_base(_Head_base&&) = default;
140
141 template<typename _UHead>
142 constexpr _Head_base(_UHead&& __h)
143 : _M_head_impl(std::forward<_UHead>(__h)) { }
144
145 _GLIBCXX20_CONSTEXPR
146 _Head_base(allocator_arg_t, __uses_alloc0)
147 : _M_head_impl() { }
148
149 template<typename _Alloc>
150 _GLIBCXX20_CONSTEXPR
151 _Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
152 : _M_head_impl(allocator_arg, *__a._M_a) { }
153
154 template<typename _Alloc>
155 _GLIBCXX20_CONSTEXPR
156 _Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
157 : _M_head_impl(*__a._M_a) { }
158
159 template<typename _UHead>
160 _GLIBCXX20_CONSTEXPR
161 _Head_base(__uses_alloc0, _UHead&& __uhead)
162 : _M_head_impl(std::forward<_UHead>(__uhead)) { }
163
164 template<typename _Alloc, typename _UHead>
165 _GLIBCXX20_CONSTEXPR
166 _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
167 : _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
168 { }
169
170 template<typename _Alloc, typename _UHead>
171 _GLIBCXX20_CONSTEXPR
172 _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
173 : _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
174
175 static constexpr _Head&
176 _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
177
178 static constexpr const _Head&
179 _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
180
181 _Head _M_head_impl;
182 };
183
184 /**
185 * Contains the actual implementation of the @c tuple template, stored
186 * as a recursive inheritance hierarchy from the first element (most
187 * derived class) to the last (least derived class). The @c Idx
188 * parameter gives the 0-based index of the element stored at this
189 * point in the hierarchy; we use it to implement a constant-time
190 * get() operation.
191 */
192 template<std::size_t _Idx, typename... _Elements>
193 struct _Tuple_impl;
194
195 /**
196 * Recursive tuple implementation. Here we store the @c Head element
197 * and derive from a @c Tuple_impl containing the remaining elements
198 * (which contains the @c Tail).
199 */
200 template<std::size_t _Idx, typename _Head, typename... _Tail>
201 struct _Tuple_impl<_Idx, _Head, _Tail...>
202 : public _Tuple_impl<_Idx + 1, _Tail...>,
203 private _Head_base<_Idx, _Head>
204 {
205 template<std::size_t, typename...> friend class _Tuple_impl;
206
207 typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
208 typedef _Head_base<_Idx, _Head> _Base;
209
210 static constexpr _Head&
211 _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
212
213 static constexpr const _Head&
214 _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
215
216 static constexpr _Inherited&
217 _M_tail(_Tuple_impl& __t) noexcept { return __t; }
218
219 static constexpr const _Inherited&
220 _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
221
222 constexpr _Tuple_impl()
223 : _Inherited(), _Base() { }
224
225 explicit
226 constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
227 : _Inherited(__tail...), _Base(__head) { }
228
229 template<typename _UHead, typename... _UTail, typename = typename
230 enable_if<sizeof...(_Tail) == sizeof...(_UTail)>::type>
231 explicit
232 constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
233 : _Inherited(std::forward<_UTail>(__tail)...),
234 _Base(std::forward<_UHead>(__head)) { }
235
236 constexpr _Tuple_impl(const _Tuple_impl&) = default;
237
238 // _GLIBCXX_RESOLVE_LIB_DEFECTS
239 // 2729. Missing SFINAE on std::pair::operator=
240 _Tuple_impl& operator=(const _Tuple_impl&) = delete;
241
242 constexpr
243 _Tuple_impl(_Tuple_impl&& __in)
244 noexcept(__and_<is_nothrow_move_constructible<_Head>,
245 is_nothrow_move_constructible<_Inherited>>::value)
246 : _Inherited(std::move(_M_tail(__in))),
247 _Base(std::forward<_Head>(_M_head(__in))) { }
248
249 template<typename... _UElements>
250 constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
251 : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
252 _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
253
254 template<typename _UHead, typename... _UTails>
255 constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
256 : _Inherited(std::move
257 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
258 _Base(std::forward<_UHead>
259 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
260
261 template<typename _Alloc>
262 _GLIBCXX20_CONSTEXPR
263 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
264 : _Inherited(__tag, __a),
265 _Base(__tag, __use_alloc<_Head>(__a)) { }
266
267 template<typename _Alloc>
268 _GLIBCXX20_CONSTEXPR
269 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
270 const _Head& __head, const _Tail&... __tail)
271 : _Inherited(__tag, __a, __tail...),
272 _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
273
274 template<typename _Alloc, typename _UHead, typename... _UTail,
275 typename = typename enable_if<sizeof...(_Tail)
276 == sizeof...(_UTail)>::type>
277 _GLIBCXX20_CONSTEXPR
278 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
279 _UHead&& __head, _UTail&&... __tail)
280 : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
281 _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
282 std::forward<_UHead>(__head)) { }
283
284 template<typename _Alloc>
285 _GLIBCXX20_CONSTEXPR
286 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
287 const _Tuple_impl& __in)
288 : _Inherited(__tag, __a, _M_tail(__in)),
289 _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
290
291 template<typename _Alloc>
292 _GLIBCXX20_CONSTEXPR
293 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
294 _Tuple_impl&& __in)
295 : _Inherited(__tag, __a, std::move(_M_tail(__in))),
296 _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
297 std::forward<_Head>(_M_head(__in))) { }
298
299 template<typename _Alloc, typename _UHead, typename... _UTails>
300 _GLIBCXX20_CONSTEXPR
301 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
302 const _Tuple_impl<_Idx, _UHead, _UTails...>& __in)
303 : _Inherited(__tag, __a,
304 _Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)),
305 _Base(__use_alloc<_Head, _Alloc, const _UHead&>(__a),
306 _Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)) { }
307
308 template<typename _Alloc, typename _UHead, typename... _UTails>
309 _GLIBCXX20_CONSTEXPR
310 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
311 _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
312 : _Inherited(__tag, __a, std::move
313 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
314 _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
315 std::forward<_UHead>
316 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
317
318 template<typename... _UElements>
319 _GLIBCXX20_CONSTEXPR
320 void
321 _M_assign(const _Tuple_impl<_Idx, _UElements...>& __in)
322 {
323 _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
324 _M_tail(*this)._M_assign(
325 _Tuple_impl<_Idx, _UElements...>::_M_tail(__in));
326 }
327
328 template<typename _UHead, typename... _UTails>
329 _GLIBCXX20_CONSTEXPR
330 void
331 _M_assign(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
332 {
333 _M_head(*this) = std::forward<_UHead>
334 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
335 _M_tail(*this)._M_assign(
336 std::move(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)));
337 }
338
339 protected:
340 _GLIBCXX20_CONSTEXPR
341 void
342 _M_swap(_Tuple_impl& __in)
343 {
344 using std::swap;
345 swap(_M_head(*this), _M_head(__in));
346 _Inherited::_M_swap(_M_tail(__in));
347 }
348 };
349
350 // Basis case of inheritance recursion.
351 template<std::size_t _Idx, typename _Head>
352 struct _Tuple_impl<_Idx, _Head>
353 : private _Head_base<_Idx, _Head>
354 {
355 template<std::size_t, typename...> friend class _Tuple_impl;
356
357 typedef _Head_base<_Idx, _Head> _Base;
358
359 static constexpr _Head&
360 _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
361
362 static constexpr const _Head&
363 _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
364
365 constexpr _Tuple_impl()
366 : _Base() { }
367
368 explicit
369 constexpr _Tuple_impl(const _Head& __head)
370 : _Base(__head) { }
371
372 template<typename _UHead>
373 explicit
374 constexpr _Tuple_impl(_UHead&& __head)
375 : _Base(std::forward<_UHead>(__head)) { }
376
377 constexpr _Tuple_impl(const _Tuple_impl&) = default;
378
379 // _GLIBCXX_RESOLVE_LIB_DEFECTS
380 // 2729. Missing SFINAE on std::pair::operator=
381 _Tuple_impl& operator=(const _Tuple_impl&) = delete;
382
383 constexpr
384 _Tuple_impl(_Tuple_impl&& __in)
385 noexcept(is_nothrow_move_constructible<_Head>::value)
386 : _Base(std::forward<_Head>(_M_head(__in))) { }
387
388 template<typename _UHead>
389 constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UHead>& __in)
390 : _Base(_Tuple_impl<_Idx, _UHead>::_M_head(__in)) { }
391
392 template<typename _UHead>
393 constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead>&& __in)
394 : _Base(std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
395 { }
396
397 template<typename _Alloc>
398 _GLIBCXX20_CONSTEXPR
399 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
400 : _Base(__tag, __use_alloc<_Head>(__a)) { }
401
402 template<typename _Alloc>
403 _GLIBCXX20_CONSTEXPR
404 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
405 const _Head& __head)
406 : _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
407
408 template<typename _Alloc, typename _UHead>
409 _GLIBCXX20_CONSTEXPR
410 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
411 _UHead&& __head)
412 : _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
413 std::forward<_UHead>(__head)) { }
414
415 template<typename _Alloc>
416 _GLIBCXX20_CONSTEXPR
417 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
418 const _Tuple_impl& __in)
419 : _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
420
421 template<typename _Alloc>
422 _GLIBCXX20_CONSTEXPR
423 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
424 _Tuple_impl&& __in)
425 : _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
426 std::forward<_Head>(_M_head(__in))) { }
427
428 template<typename _Alloc, typename _UHead>
429 _GLIBCXX20_CONSTEXPR
430 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
431 const _Tuple_impl<_Idx, _UHead>& __in)
432 : _Base(__use_alloc<_Head, _Alloc, const _UHead&>(__a),
433 _Tuple_impl<_Idx, _UHead>::_M_head(__in)) { }
434
435 template<typename _Alloc, typename _UHead>
436 _GLIBCXX20_CONSTEXPR
437 _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
438 _Tuple_impl<_Idx, _UHead>&& __in)
439 : _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
440 std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
441 { }
442
443 template<typename _UHead>
444 _GLIBCXX20_CONSTEXPR
445 void
446 _M_assign(const _Tuple_impl<_Idx, _UHead>& __in)
447 {
448 _M_head(*this) = _Tuple_impl<_Idx, _UHead>::_M_head(__in);
449 }
450
451 template<typename _UHead>
452 _GLIBCXX20_CONSTEXPR
453 void
454 _M_assign(_Tuple_impl<_Idx, _UHead>&& __in)
455 {
456 _M_head(*this)
457 = std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in));
458 }
459
460 protected:
461 _GLIBCXX20_CONSTEXPR
462 void
463 _M_swap(_Tuple_impl& __in)
464 {
465 using std::swap;
466 swap(_M_head(*this), _M_head(__in));
467 }
468 };
469
470 // Concept utility functions, reused in conditionally-explicit
471 // constructors.
472 template<bool, typename... _Types>
473 struct _TupleConstraints
474 {
475 template<typename _Tp, typename _Up> // Workaround for PR 96592
476 using is_constructible
477 = __bool_constant<__is_constructible(_Tp, _Up)>;
478
479 // Constraint for a non-explicit constructor.
480 // True iff each Ti in _Types... can be constructed from Ui in _UTypes...
481 // and every Ui is implicitly convertible to Ti.
482 template<typename... _UTypes>
483 static constexpr bool __is_implicitly_constructible()
484 {
485 return __and_<is_constructible<_Types, _UTypes>...,
486 is_convertible<_UTypes, _Types>...
487 >::value;
488 }
489
490 // Constraint for a non-explicit constructor.
491 // True iff each Ti in _Types... can be constructed from Ui in _UTypes...
492 // but not every Ui is implicitly convertible to Ti.
493 template<typename... _UTypes>
494 static constexpr bool __is_explicitly_constructible()
495 {
496 return __and_<is_constructible<_Types, _UTypes>...,
497 __not_<__and_<is_convertible<_UTypes, _Types>...>>
498 >::value;
499 }
500
501 static constexpr bool __is_implicitly_default_constructible()
502 {
503 return __and_<std::__is_implicitly_default_constructible<_Types>...
504 >::value;
505 }
506
507 static constexpr bool __is_explicitly_default_constructible()
508 {
509 return __and_<is_default_constructible<_Types>...,
510 __not_<__and_<
511 std::__is_implicitly_default_constructible<_Types>...>
512 >>::value;
513 }
514 };
515
516 // Partial specialization used when a required precondition isn't met,
517 // e.g. when sizeof...(_Types) != sizeof...(_UTypes).
518 template<typename... _Types>
519 struct _TupleConstraints<false, _Types...>
520 {
521 template<typename... _UTypes>
522 static constexpr bool __is_implicitly_constructible()
523 { return false; }
524
525 template<typename... _UTypes>
526 static constexpr bool __is_explicitly_constructible()
527 { return false; }
528 };
529
530 /// Primary class template, tuple
531 template<typename... _Elements>
532 class tuple : public _Tuple_impl<0, _Elements...>
533 {
534 typedef _Tuple_impl<0, _Elements...> _Inherited;
535
536 template<bool _Cond>
537 using _TCC = _TupleConstraints<_Cond, _Elements...>;
538
539 // Constraint for non-explicit default constructor
540 template<bool _Dummy>
541 using _ImplicitDefaultCtor = __enable_if_t<
542 _TCC<_Dummy>::__is_implicitly_default_constructible(),
543 bool>;
544
545 // Constraint for explicit default constructor
546 template<bool _Dummy>
547 using _ExplicitDefaultCtor = __enable_if_t<
548 _TCC<_Dummy>::__is_explicitly_default_constructible(),
549 bool>;
550
551 // Constraint for non-explicit constructors
552 template<bool _Cond, typename... _Args>
553 using _ImplicitCtor = __enable_if_t<
554 _TCC<_Cond>::template __is_implicitly_constructible<_Args...>(),
555 bool>;
556
557 // Constraint for non-explicit constructors
558 template<bool _Cond, typename... _Args>
559 using _ExplicitCtor = __enable_if_t<
560 _TCC<_Cond>::template __is_explicitly_constructible<_Args...>(),
561 bool>;
562
563 template<typename... _UElements>
564 static constexpr
565 __enable_if_t<sizeof...(_UElements) == sizeof...(_Elements), bool>
566 __assignable()
567 { return __and_<is_assignable<_Elements&, _UElements>...>::value; }
568
569 // Condition for noexcept-specifier of an assignment operator.
570 template<typename... _UElements>
571 static constexpr bool __nothrow_assignable()
572 {
573 return
574 __and_<is_nothrow_assignable<_Elements&, _UElements>...>::value;
575 }
576
577 // Condition for noexcept-specifier of a constructor.
578 template<typename... _UElements>
579 static constexpr bool __nothrow_constructible()
580 {
581 return
582 __and_<is_nothrow_constructible<_Elements, _UElements>...>::value;
583 }
584
585 // Constraint for tuple(_UTypes&&...) where sizeof...(_UTypes) == 1.
586 template<typename _Up>
587 static constexpr bool __valid_args()
588 {
589 return sizeof...(_Elements) == 1
590 && !is_same<tuple, __remove_cvref_t<_Up>>::value;
591 }
592
593 // Constraint for tuple(_UTypes&&...) where sizeof...(_UTypes) > 1.
594 template<typename, typename, typename... _Tail>
595 static constexpr bool __valid_args()
596 { return (sizeof...(_Tail) + 2) == sizeof...(_Elements); }
597
598 /* Constraint for constructors with a tuple<UTypes...> parameter ensures
599 * that the constructor is only viable when it would not interfere with
600 * tuple(UTypes&&...) or tuple(const tuple&) or tuple(tuple&&).
601 * Such constructors are only viable if:
602 * either sizeof...(Types) != 1,
603 * or (when Types... expands to T and UTypes... expands to U)
604 * is_convertible_v<TUPLE, T>, is_constructible_v<T, TUPLE>,
605 * and is_same_v<T, U> are all false.
606 */
607 template<typename _Tuple, typename = tuple,
608 typename = __remove_cvref_t<_Tuple>>
609 struct _UseOtherCtor
610 : false_type
611 { };
612 // If TUPLE is convertible to the single element in *this,
613 // then TUPLE should match tuple(UTypes&&...) instead.
614 template<typename _Tuple, typename _Tp, typename _Up>
615 struct _UseOtherCtor<_Tuple, tuple<_Tp>, tuple<_Up>>
616 : __or_<is_convertible<_Tuple, _Tp>, is_constructible<_Tp, _Tuple>>
617 { };
618 // If TUPLE and *this each have a single element of the same type,
619 // then TUPLE should match a copy/move constructor instead.
620 template<typename _Tuple, typename _Tp>
621 struct _UseOtherCtor<_Tuple, tuple<_Tp>, tuple<_Tp>>
622 : true_type
623 { };
624
625 // Return true iff sizeof...(Types) == 1 && tuple_size_v<TUPLE> == 1
626 // and the single element in Types can be initialized from TUPLE,
627 // or is the same type as tuple_element_t<0, TUPLE>.
628 template<typename _Tuple>
629 static constexpr bool __use_other_ctor()
630 { return _UseOtherCtor<_Tuple>::value; }
631
632 public:
633 template<typename _Dummy = void,
634 _ImplicitDefaultCtor<is_void<_Dummy>::value> = true>
635 constexpr
636 tuple()
637 noexcept(__and_<is_nothrow_default_constructible<_Elements>...>::value)
638 : _Inherited() { }
639
640 template<typename _Dummy = void,
641 _ExplicitDefaultCtor<is_void<_Dummy>::value> = false>
642 explicit constexpr
643 tuple()
644 noexcept(__and_<is_nothrow_default_constructible<_Elements>...>::value)
645 : _Inherited() { }
646
647 template<bool _NotEmpty = (sizeof...(_Elements) >= 1),
648 _ImplicitCtor<_NotEmpty, const _Elements&...> = true>
649 constexpr
650 tuple(const _Elements&... __elements)
651 noexcept(__nothrow_constructible<const _Elements&...>())
652 : _Inherited(__elements...) { }
653
654 template<bool _NotEmpty = (sizeof...(_Elements) >= 1),
655 _ExplicitCtor<_NotEmpty, const _Elements&...> = false>
656 explicit constexpr
657 tuple(const _Elements&... __elements)
658 noexcept(__nothrow_constructible<const _Elements&...>())
659 : _Inherited(__elements...) { }
660
661 template<typename... _UElements,
662 bool _Valid = __valid_args<_UElements...>(),
663 _ImplicitCtor<_Valid, _UElements...> = true>
664 constexpr
665 tuple(_UElements&&... __elements)
666 noexcept(__nothrow_constructible<_UElements...>())
667 : _Inherited(std::forward<_UElements>(__elements)...) { }
668
669 template<typename... _UElements,
670 bool _Valid = __valid_args<_UElements...>(),
671 _ExplicitCtor<_Valid, _UElements...> = false>
672 explicit constexpr
673 tuple(_UElements&&... __elements)
674 noexcept(__nothrow_constructible<_UElements...>())
675 : _Inherited(std::forward<_UElements>(__elements)...) { }
676
677 constexpr tuple(const tuple&) = default;
678
679 constexpr tuple(tuple&&) = default;
680
681 template<typename... _UElements,
682 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
683 && !__use_other_ctor<const tuple<_UElements...>&>(),
684 _ImplicitCtor<_Valid, const _UElements&...> = true>
685 constexpr
686 tuple(const tuple<_UElements...>& __in)
687 noexcept(__nothrow_constructible<const _UElements&...>())
688 : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
689 { }
690
691 template<typename... _UElements,
692 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
693 && !__use_other_ctor<const tuple<_UElements...>&>(),
694 _ExplicitCtor<_Valid, const _UElements&...> = false>
695 explicit constexpr
696 tuple(const tuple<_UElements...>& __in)
697 noexcept(__nothrow_constructible<const _UElements&...>())
698 : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
699 { }
700
701 template<typename... _UElements,
702 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
703 && !__use_other_ctor<tuple<_UElements...>&&>(),
704 _ImplicitCtor<_Valid, _UElements...> = true>
705 constexpr
706 tuple(tuple<_UElements...>&& __in)
707 noexcept(__nothrow_constructible<_UElements...>())
708 : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
709
710 template<typename... _UElements,
711 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
712 && !__use_other_ctor<tuple<_UElements...>&&>(),
713 _ExplicitCtor<_Valid, _UElements...> = false>
714 explicit constexpr
715 tuple(tuple<_UElements...>&& __in)
716 noexcept(__nothrow_constructible<_UElements...>())
717 : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
718
719 // Allocator-extended constructors.
720
721 template<typename _Alloc,
722 _ImplicitDefaultCtor<is_object<_Alloc>::value> = true>
723 _GLIBCXX20_CONSTEXPR
724 tuple(allocator_arg_t __tag, const _Alloc& __a)
725 : _Inherited(__tag, __a) { }
726
727 template<typename _Alloc, bool _NotEmpty = (sizeof...(_Elements) >= 1),
728 _ImplicitCtor<_NotEmpty, const _Elements&...> = true>
729 _GLIBCXX20_CONSTEXPR
730 tuple(allocator_arg_t __tag, const _Alloc& __a,
731 const _Elements&... __elements)
732 : _Inherited(__tag, __a, __elements...) { }
733
734 template<typename _Alloc, bool _NotEmpty = (sizeof...(_Elements) >= 1),
735 _ExplicitCtor<_NotEmpty, const _Elements&...> = false>
736 _GLIBCXX20_CONSTEXPR
737 explicit
738 tuple(allocator_arg_t __tag, const _Alloc& __a,
739 const _Elements&... __elements)
740 : _Inherited(__tag, __a, __elements...) { }
741
742 template<typename _Alloc, typename... _UElements,
743 bool _Valid = __valid_args<_UElements...>(),
744 _ImplicitCtor<_Valid, _UElements...> = true>
745 _GLIBCXX20_CONSTEXPR
746 tuple(allocator_arg_t __tag, const _Alloc& __a,
747 _UElements&&... __elements)
748 : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
749 { }
750
751 template<typename _Alloc, typename... _UElements,
752 bool _Valid = __valid_args<_UElements...>(),
753 _ExplicitCtor<_Valid, _UElements...> = false>
754 _GLIBCXX20_CONSTEXPR
755 explicit
756 tuple(allocator_arg_t __tag, const _Alloc& __a,
757 _UElements&&... __elements)
758 : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
759 { }
760
761 template<typename _Alloc>
762 _GLIBCXX20_CONSTEXPR
763 tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
764 : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
765
766 template<typename _Alloc>
767 _GLIBCXX20_CONSTEXPR
768 tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
769 : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
770
771 template<typename _Alloc, typename... _UElements,
772 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
773 && !__use_other_ctor<const tuple<_UElements...>&>(),
774 _ImplicitCtor<_Valid, const _UElements&...> = true>
775 _GLIBCXX20_CONSTEXPR
776 tuple(allocator_arg_t __tag, const _Alloc& __a,
777 const tuple<_UElements...>& __in)
778 : _Inherited(__tag, __a,
779 static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
780 { }
781
782 template<typename _Alloc, typename... _UElements,
783 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
784 && !__use_other_ctor<const tuple<_UElements...>&>(),
785 _ExplicitCtor<_Valid, const _UElements&...> = false>
786 _GLIBCXX20_CONSTEXPR
787 explicit
788 tuple(allocator_arg_t __tag, const _Alloc& __a,
789 const tuple<_UElements...>& __in)
790 : _Inherited(__tag, __a,
791 static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
792 { }
793
794 template<typename _Alloc, typename... _UElements,
795 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
796 && !__use_other_ctor<tuple<_UElements...>&&>(),
797 _ImplicitCtor<_Valid, _UElements...> = true>
798 _GLIBCXX20_CONSTEXPR
799 tuple(allocator_arg_t __tag, const _Alloc& __a,
800 tuple<_UElements...>&& __in)
801 : _Inherited(__tag, __a,
802 static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
803 { }
804
805 template<typename _Alloc, typename... _UElements,
806 bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
807 && !__use_other_ctor<tuple<_UElements...>&&>(),
808 _ExplicitCtor<_Valid, _UElements...> = false>
809 _GLIBCXX20_CONSTEXPR
810 explicit
811 tuple(allocator_arg_t __tag, const _Alloc& __a,
812 tuple<_UElements...>&& __in)
813 : _Inherited(__tag, __a,
814 static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
815 { }
816
817 // tuple assignment
818
819 _GLIBCXX20_CONSTEXPR
820 tuple&
821 operator=(typename conditional<__assignable<const _Elements&...>(),
822 const tuple&,
823 const __nonesuch&>::type __in)
824 noexcept(__nothrow_assignable<const _Elements&...>())
825 {
826 this->_M_assign(__in);
827 return *this;
828 }
829
830 _GLIBCXX20_CONSTEXPR
831 tuple&
832 operator=(typename conditional<__assignable<_Elements...>(),
833 tuple&&,
834 __nonesuch&&>::type __in)
835 noexcept(__nothrow_assignable<_Elements...>())
836 {
837 this->_M_assign(std::move(__in));
838 return *this;
839 }
840
841 template<typename... _UElements>
842 _GLIBCXX20_CONSTEXPR
843 __enable_if_t<__assignable<const _UElements&...>(), tuple&>
844 operator=(const tuple<_UElements...>& __in)
845 noexcept(__nothrow_assignable<const _UElements&...>())
846 {
847 this->_M_assign(__in);
848 return *this;
849 }
850
851 template<typename... _UElements>
852 _GLIBCXX20_CONSTEXPR
853 __enable_if_t<__assignable<_UElements...>(), tuple&>
854 operator=(tuple<_UElements...>&& __in)
855 noexcept(__nothrow_assignable<_UElements...>())
856 {
857 this->_M_assign(std::move(__in));
858 return *this;
859 }
860
861 // tuple swap
862 _GLIBCXX20_CONSTEXPR
863 void
864 swap(tuple& __in)
865 noexcept(__and_<__is_nothrow_swappable<_Elements>...>::value)
866 { _Inherited::_M_swap(__in); }
867 };
868
869#if __cpp_deduction_guides >= 201606
870 template<typename... _UTypes>
871 tuple(_UTypes...) -> tuple<_UTypes...>;
872 template<typename _T1, typename _T2>
873 tuple(pair<_T1, _T2>) -> tuple<_T1, _T2>;
874 template<typename _Alloc, typename... _UTypes>
875 tuple(allocator_arg_t, _Alloc, _UTypes...) -> tuple<_UTypes...>;
876 template<typename _Alloc, typename _T1, typename _T2>
877 tuple(allocator_arg_t, _Alloc, pair<_T1, _T2>) -> tuple<_T1, _T2>;
878 template<typename _Alloc, typename... _UTypes>
879 tuple(allocator_arg_t, _Alloc, tuple<_UTypes...>) -> tuple<_UTypes...>;
880#endif
881
882 // Explicit specialization, zero-element tuple.
883 template<>
884 class tuple<>
885 {
886 public:
887 _GLIBCXX20_CONSTEXPR
888 void swap(tuple&) noexcept { /* no-op */ }
889 // We need the default since we're going to define no-op
890 // allocator constructors.
891 tuple() = default;
892 // No-op allocator constructors.
893 template<typename _Alloc>
894 _GLIBCXX20_CONSTEXPR
895 tuple(allocator_arg_t, const _Alloc&) noexcept { }
896 template<typename _Alloc>
897 _GLIBCXX20_CONSTEXPR
898 tuple(allocator_arg_t, const _Alloc&, const tuple&) noexcept { }
899 };
900
901 /// Partial specialization, 2-element tuple.
902 /// Includes construction and assignment from a pair.
903 template<typename _T1, typename _T2>
904 class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
905 {
906 typedef _Tuple_impl<0, _T1, _T2> _Inherited;
907
908 // Constraint for non-explicit default constructor
909 template<bool _Dummy, typename _U1, typename _U2>
910 using _ImplicitDefaultCtor = __enable_if_t<
911 _TupleConstraints<_Dummy, _U1, _U2>::
912 __is_implicitly_default_constructible(),
913 bool>;
914
915 // Constraint for explicit default constructor
916 template<bool _Dummy, typename _U1, typename _U2>
917 using _ExplicitDefaultCtor = __enable_if_t<
918 _TupleConstraints<_Dummy, _U1, _U2>::
919 __is_explicitly_default_constructible(),
920 bool>;
921
922 template<bool _Dummy>
923 using _TCC = _TupleConstraints<_Dummy, _T1, _T2>;
924
925 // Constraint for non-explicit constructors
926 template<bool _Cond, typename _U1, typename _U2>
927 using _ImplicitCtor = __enable_if_t<
928 _TCC<_Cond>::template __is_implicitly_constructible<_U1, _U2>(),
929 bool>;
930
931 // Constraint for non-explicit constructors
932 template<bool _Cond, typename _U1, typename _U2>
933 using _ExplicitCtor = __enable_if_t<
934 _TCC<_Cond>::template __is_explicitly_constructible<_U1, _U2>(),
935 bool>;
936
937 template<typename _U1, typename _U2>
938 static constexpr bool __assignable()
939 {
940 return __and_<is_assignable<_T1&, _U1>,
941 is_assignable<_T2&, _U2>>::value;
942 }
943
944 template<typename _U1, typename _U2>
945 static constexpr bool __nothrow_assignable()
946 {
947 return __and_<is_nothrow_assignable<_T1&, _U1>,
948 is_nothrow_assignable<_T2&, _U2>>::value;
949 }
950
951 template<typename _U1, typename _U2>
952 static constexpr bool __nothrow_constructible()
953 {
954 return __and_<is_nothrow_constructible<_T1, _U1>,
955 is_nothrow_constructible<_T2, _U2>>::value;
956 }
957
958 static constexpr bool __nothrow_default_constructible()
959 {
960 return __and_<is_nothrow_default_constructible<_T1>,
961 is_nothrow_default_constructible<_T2>>::value;
962 }
963
964 template<typename _U1>
965 static constexpr bool __is_alloc_arg()
966 { return is_same<__remove_cvref_t<_U1>, allocator_arg_t>::value; }
967
968 public:
969 template<bool _Dummy = true,
970 _ImplicitDefaultCtor<_Dummy, _T1, _T2> = true>
971 constexpr
972 tuple()
973 noexcept(__nothrow_default_constructible())
974 : _Inherited() { }
975
976 template<bool _Dummy = true,
977 _ExplicitDefaultCtor<_Dummy, _T1, _T2> = false>
978 explicit constexpr
979 tuple()
980 noexcept(__nothrow_default_constructible())
981 : _Inherited() { }
982
983 template<bool _Dummy = true,
984 _ImplicitCtor<_Dummy, const _T1&, const _T2&> = true>
985 constexpr
986 tuple(const _T1& __a1, const _T2& __a2)
987 noexcept(__nothrow_constructible<const _T1&, const _T2&>())
988 : _Inherited(__a1, __a2) { }
989
990 template<bool _Dummy = true,
991 _ExplicitCtor<_Dummy, const _T1&, const _T2&> = false>
992 explicit constexpr
993 tuple(const _T1& __a1, const _T2& __a2)
994 noexcept(__nothrow_constructible<const _T1&, const _T2&>())
995 : _Inherited(__a1, __a2) { }
996
997 template<typename _U1, typename _U2,
998 _ImplicitCtor<!__is_alloc_arg<_U1>(), _U1, _U2> = true>
999 constexpr
1000 tuple(_U1&& __a1, _U2&& __a2)
1001 noexcept(__nothrow_constructible<_U1, _U2>())
1002 : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
1003
1004 template<typename _U1, typename _U2,
1005 _ExplicitCtor<!__is_alloc_arg<_U1>(), _U1, _U2> = false>
1006 explicit constexpr
1007 tuple(_U1&& __a1, _U2&& __a2)
1008 noexcept(__nothrow_constructible<_U1, _U2>())
1009 : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
1010
1011 constexpr tuple(const tuple&) = default;
1012
1013 constexpr tuple(tuple&&) = default;
1014
1015 template<typename _U1, typename _U2,
1016 _ImplicitCtor<true, const _U1&, const _U2&> = true>
1017 constexpr
1018 tuple(const tuple<_U1, _U2>& __in)
1019 noexcept(__nothrow_constructible<const _U1&, const _U2&>())
1020 : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
1021
1022 template<typename _U1, typename _U2,
1023 _ExplicitCtor<true, const _U1&, const _U2&> = false>
1024 explicit constexpr
1025 tuple(const tuple<_U1, _U2>& __in)
1026 noexcept(__nothrow_constructible<const _U1&, const _U2&>())
1027 : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
1028
1029 template<typename _U1, typename _U2,
1030 _ImplicitCtor<true, _U1, _U2> = true>
1031 constexpr
1032 tuple(tuple<_U1, _U2>&& __in)
1033 noexcept(__nothrow_constructible<_U1, _U2>())
1034 : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
1035
1036 template<typename _U1, typename _U2,
1037 _ExplicitCtor<true, _U1, _U2> = false>
1038 explicit constexpr
1039 tuple(tuple<_U1, _U2>&& __in)
1040 noexcept(__nothrow_constructible<_U1, _U2>())
1041 : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
1042
1043 template<typename _U1, typename _U2,
1044 _ImplicitCtor<true, const _U1&, const _U2&> = true>
1045 constexpr
1046 tuple(const pair<_U1, _U2>& __in)
1047 noexcept(__nothrow_constructible<const _U1&, const _U2&>())
1048 : _Inherited(__in.first, __in.second) { }
1049
1050 template<typename _U1, typename _U2,
1051 _ExplicitCtor<true, const _U1&, const _U2&> = false>
1052 explicit constexpr
1053 tuple(const pair<_U1, _U2>& __in)
1054 noexcept(__nothrow_constructible<const _U1&, const _U2&>())
1055 : _Inherited(__in.first, __in.second) { }
1056
1057 template<typename _U1, typename _U2,
1058 _ImplicitCtor<true, _U1, _U2> = true>
1059 constexpr
1060 tuple(pair<_U1, _U2>&& __in)
1061 noexcept(__nothrow_constructible<_U1, _U2>())
1062 : _Inherited(std::forward<_U1>(__in.first),
1063 std::forward<_U2>(__in.second)) { }
1064
1065 template<typename _U1, typename _U2,
1066 _ExplicitCtor<true, _U1, _U2> = false>
1067 explicit constexpr
1068 tuple(pair<_U1, _U2>&& __in)
1069 noexcept(__nothrow_constructible<_U1, _U2>())
1070 : _Inherited(std::forward<_U1>(__in.first),
1071 std::forward<_U2>(__in.second)) { }
1072
1073 // Allocator-extended constructors.
1074
1075 template<typename _Alloc,
1076 _ImplicitDefaultCtor<is_object<_Alloc>::value, _T1, _T2> = true>
1077 _GLIBCXX20_CONSTEXPR
1078 tuple(allocator_arg_t __tag, const _Alloc& __a)
1079 : _Inherited(__tag, __a) { }
1080
1081 template<typename _Alloc, bool _Dummy = true,
1082 _ImplicitCtor<_Dummy, const _T1&, const _T2&> = true>
1083 _GLIBCXX20_CONSTEXPR
1084 tuple(allocator_arg_t __tag, const _Alloc& __a,
1085 const _T1& __a1, const _T2& __a2)
1086 : _Inherited(__tag, __a, __a1, __a2) { }
1087
1088 template<typename _Alloc, bool _Dummy = true,
1089 _ExplicitCtor<_Dummy, const _T1&, const _T2&> = false>
1090 explicit
1091 _GLIBCXX20_CONSTEXPR
1092 tuple(allocator_arg_t __tag, const _Alloc& __a,
1093 const _T1& __a1, const _T2& __a2)
1094 : _Inherited(__tag, __a, __a1, __a2) { }
1095
1096 template<typename _Alloc, typename _U1, typename _U2,
1097 _ImplicitCtor<true, _U1, _U2> = true>
1098 _GLIBCXX20_CONSTEXPR
1099 tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
1100 : _Inherited(__tag, __a, std::forward<_U1>(__a1),
1101 std::forward<_U2>(__a2)) { }
1102
1103 template<typename _Alloc, typename _U1, typename _U2,
1104 _ExplicitCtor<true, _U1, _U2> = false>
1105 explicit
1106 _GLIBCXX20_CONSTEXPR
1107 tuple(allocator_arg_t __tag, const _Alloc& __a,
1108 _U1&& __a1, _U2&& __a2)
1109 : _Inherited(__tag, __a, std::forward<_U1>(__a1),
1110 std::forward<_U2>(__a2)) { }
1111
1112 template<typename _Alloc>
1113 _GLIBCXX20_CONSTEXPR
1114 tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
1115 : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
1116
1117 template<typename _Alloc>
1118 _GLIBCXX20_CONSTEXPR
1119 tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
1120 : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
1121
1122 template<typename _Alloc, typename _U1, typename _U2,
1123 _ImplicitCtor<true, const _U1&, const _U2&> = true>
1124 _GLIBCXX20_CONSTEXPR
1125 tuple(allocator_arg_t __tag, const _Alloc& __a,
1126 const tuple<_U1, _U2>& __in)
1127 : _Inherited(__tag, __a,
1128 static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
1129 { }
1130
1131 template<typename _Alloc, typename _U1, typename _U2,
1132 _ExplicitCtor<true, const _U1&, const _U2&> = false>
1133 explicit
1134 _GLIBCXX20_CONSTEXPR
1135 tuple(allocator_arg_t __tag, const _Alloc& __a,
1136 const tuple<_U1, _U2>& __in)
1137 : _Inherited(__tag, __a,
1138 static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
1139 { }
1140
1141 template<typename _Alloc, typename _U1, typename _U2,
1142 _ImplicitCtor<true, _U1, _U2> = true>
1143 _GLIBCXX20_CONSTEXPR
1144 tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
1145 : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
1146 { }
1147
1148 template<typename _Alloc, typename _U1, typename _U2,
1149 _ExplicitCtor<true, _U1, _U2> = false>
1150 explicit
1151 _GLIBCXX20_CONSTEXPR
1152 tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
1153 : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
1154 { }
1155
1156 template<typename _Alloc, typename _U1, typename _U2,
1157 _ImplicitCtor<true, const _U1&, const _U2&> = true>
1158 _GLIBCXX20_CONSTEXPR
1159 tuple(allocator_arg_t __tag, const _Alloc& __a,
1160 const pair<_U1, _U2>& __in)
1161 : _Inherited(__tag, __a, __in.first, __in.second) { }
1162
1163 template<typename _Alloc, typename _U1, typename _U2,
1164 _ExplicitCtor<true, const _U1&, const _U2&> = false>
1165 explicit
1166 _GLIBCXX20_CONSTEXPR
1167 tuple(allocator_arg_t __tag, const _Alloc& __a,
1168 const pair<_U1, _U2>& __in)
1169 : _Inherited(__tag, __a, __in.first, __in.second) { }
1170
1171 template<typename _Alloc, typename _U1, typename _U2,
1172 _ImplicitCtor<true, _U1, _U2> = true>
1173 _GLIBCXX20_CONSTEXPR
1174 tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
1175 : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
1176 std::forward<_U2>(__in.second)) { }
1177
1178 template<typename _Alloc, typename _U1, typename _U2,
1179 _ExplicitCtor<true, _U1, _U2> = false>
1180 explicit
1181 _GLIBCXX20_CONSTEXPR
1182 tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
1183 : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
1184 std::forward<_U2>(__in.second)) { }
1185
1186 // Tuple assignment.
1187
1188 _GLIBCXX20_CONSTEXPR
1189 tuple&
1190 operator=(typename conditional<__assignable<const _T1&, const _T2&>(),
1191 const tuple&,
1192 const __nonesuch&>::type __in)
1193 noexcept(__nothrow_assignable<const _T1&, const _T2&>())
1194 {
1195 this->_M_assign(__in);
1196 return *this;
1197 }
1198
1199 _GLIBCXX20_CONSTEXPR
1200 tuple&
1201 operator=(typename conditional<__assignable<_T1, _T2>(),
1202 tuple&&,
1203 __nonesuch&&>::type __in)
1204 noexcept(__nothrow_assignable<_T1, _T2>())
1205 {
1206 this->_M_assign(std::move(__in));
1207 return *this;
1208 }
1209
1210 template<typename _U1, typename _U2>
1211 _GLIBCXX20_CONSTEXPR
1212 __enable_if_t<__assignable<const _U1&, const _U2&>(), tuple&>
1213 operator=(const tuple<_U1, _U2>& __in)
1214 noexcept(__nothrow_assignable<const _U1&, const _U2&>())
1215 {
1216 this->_M_assign(__in);
1217 return *this;
1218 }
1219
1220 template<typename _U1, typename _U2>
1221 _GLIBCXX20_CONSTEXPR
1222 __enable_if_t<__assignable<_U1, _U2>(), tuple&>
1223 operator=(tuple<_U1, _U2>&& __in)
1224 noexcept(__nothrow_assignable<_U1, _U2>())
1225 {
1226 this->_M_assign(std::move(__in));
1227 return *this;
1228 }
1229
1230 template<typename _U1, typename _U2>
1231 _GLIBCXX20_CONSTEXPR
1232 __enable_if_t<__assignable<const _U1&, const _U2&>(), tuple&>
1233 operator=(const pair<_U1, _U2>& __in)
1234 noexcept(__nothrow_assignable<const _U1&, const _U2&>())
1235 {
1236 this->_M_head(*this) = __in.first;
1237 this->_M_tail(*this)._M_head(*this) = __in.second;
1238 return *this;
1239 }
1240
1241 template<typename _U1, typename _U2>
1242 _GLIBCXX20_CONSTEXPR
1243 __enable_if_t<__assignable<_U1, _U2>(), tuple&>
1244 operator=(pair<_U1, _U2>&& __in)
1245 noexcept(__nothrow_assignable<_U1, _U2>())
1246 {
1247 this->_M_head(*this) = std::forward<_U1>(__in.first);
1248 this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
1249 return *this;
1250 }
1251
1252 _GLIBCXX20_CONSTEXPR
1253 void
1254 swap(tuple& __in)
1255 noexcept(__and_<__is_nothrow_swappable<_T1>,
1256 __is_nothrow_swappable<_T2>>::value)
1257 { _Inherited::_M_swap(__in); }
1258 };
1259
1260
1261 /// class tuple_size
1262 template<typename... _Elements>
1263 struct tuple_size<tuple<_Elements...>>
1264 : public integral_constant<std::size_t, sizeof...(_Elements)> { };
1265
1266#if __cplusplus > 201402L
1267 template <typename _Tp>
1268 inline constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
1269#endif
1270
1271 /**
1272 * Recursive case for tuple_element: strip off the first element in
1273 * the tuple and retrieve the (i-1)th element of the remaining tuple.
1274 */
1275 template<std::size_t __i, typename _Head, typename... _Tail>
1276 struct tuple_element<__i, tuple<_Head, _Tail...> >
1277 : tuple_element<__i - 1, tuple<_Tail...> > { };
1278
1279 /**
1280 * Basis case for tuple_element: The first element is the one we're seeking.
1281 */
1282 template<typename _Head, typename... _Tail>
1283 struct tuple_element<0, tuple<_Head, _Tail...> >
1284 {
1285 typedef _Head type;
1286 };
1287
1288 /**
1289 * Error case for tuple_element: invalid index.
1290 */
1291 template<size_t __i>
1292 struct tuple_element<__i, tuple<>>
1293 {
1294 static_assert(__i < tuple_size<tuple<>>::value,
1295 "tuple index is in range");
1296 };
1297
1298 template<std::size_t __i, typename _Head, typename... _Tail>
1299 constexpr _Head&
1300 __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1301 { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1302
1303 template<std::size_t __i, typename _Head, typename... _Tail>
1304 constexpr const _Head&
1305 __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1306 { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1307
1308 /// Return a reference to the ith element of a tuple.
1309 template<std::size_t __i, typename... _Elements>
1310 constexpr __tuple_element_t<__i, tuple<_Elements...>>&
1311 get(tuple<_Elements...>& __t) noexcept
1312 { return std::__get_helper<__i>(__t); }
1313
1314 /// Return a const reference to the ith element of a const tuple.
1315 template<std::size_t __i, typename... _Elements>
1316 constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
1317 get(const tuple<_Elements...>& __t) noexcept
1318 { return std::__get_helper<__i>(__t); }
1319
1320 /// Return an rvalue reference to the ith element of a tuple rvalue.
1321 template<std::size_t __i, typename... _Elements>
1322 constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
1323 get(tuple<_Elements...>&& __t) noexcept
1324 {
1325 typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
1326 return std::forward<__element_type&&>(std::get<__i>(__t));
1327 }
1328
1329 /// Return a const rvalue reference to the ith element of a const tuple rvalue.
1330 template<std::size_t __i, typename... _Elements>
1331 constexpr const __tuple_element_t<__i, tuple<_Elements...>>&&
1332 get(const tuple<_Elements...>&& __t) noexcept
1333 {
1334 typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
1335 return std::forward<const __element_type&&>(std::get<__i>(__t));
1336 }
1337
1338#if __cplusplus >= 201402L
1339
1340#define __cpp_lib_tuples_by_type 201304
1341
1342 template<typename _Head, size_t __i, typename... _Tail>
1343 constexpr _Head&
1344 __get_helper2(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1345 { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1346
1347 template<typename _Head, size_t __i, typename... _Tail>
1348 constexpr const _Head&
1349 __get_helper2(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1350 { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1351
1352 /// Return a reference to the unique element of type _Tp of a tuple.
1353 template <typename _Tp, typename... _Types>
1354 constexpr _Tp&
1355 get(tuple<_Types...>& __t) noexcept
1356 { return std::__get_helper2<_Tp>(__t); }
1357
1358 /// Return a reference to the unique element of type _Tp of a tuple rvalue.
1359 template <typename _Tp, typename... _Types>
1360 constexpr _Tp&&
1361 get(tuple<_Types...>&& __t) noexcept
1362 { return std::forward<_Tp&&>(std::__get_helper2<_Tp>(__t)); }
1363
1364 /// Return a const reference to the unique element of type _Tp of a tuple.
1365 template <typename _Tp, typename... _Types>
1366 constexpr const _Tp&
1367 get(const tuple<_Types...>& __t) noexcept
1368 { return std::__get_helper2<_Tp>(__t); }
1369
1370 /// Return a const reference to the unique element of type _Tp of
1371 /// a const tuple rvalue.
1372 template <typename _Tp, typename... _Types>
1373 constexpr const _Tp&&
1374 get(const tuple<_Types...>&& __t) noexcept
1375 { return std::forward<const _Tp&&>(std::__get_helper2<_Tp>(__t)); }
1376#endif
1377
1378 // This class performs the comparison operations on tuples
1379 template<typename _Tp, typename _Up, size_t __i, size_t __size>
1380 struct __tuple_compare
1381 {
1382 static constexpr bool
1383 __eq(const _Tp& __t, const _Up& __u)
1384 {
1385 return bool(std::get<__i>(__t) == std::get<__i>(__u))
1386 && __tuple_compare<_Tp, _Up, __i + 1, __size>::__eq(__t, __u);
1387 }
1388
1389 static constexpr bool
1390 __less(const _Tp& __t, const _Up& __u)
1391 {
1392 return bool(std::get<__i>(__t) < std::get<__i>(__u))
1393 || (!bool(std::get<__i>(__u) < std::get<__i>(__t))
1394 && __tuple_compare<_Tp, _Up, __i + 1, __size>::__less(__t, __u));
1395 }
1396 };
1397
1398 template<typename _Tp, typename _Up, size_t __size>
1399 struct __tuple_compare<_Tp, _Up, __size, __size>
1400 {
1401 static constexpr bool
1402 __eq(const _Tp&, const _Up&) { return true; }
1403
1404 static constexpr bool
1405 __less(const _Tp&, const _Up&) { return false; }
1406 };
1407
1408 template<typename... _TElements, typename... _UElements>
1409 constexpr bool
1410 operator==(const tuple<_TElements...>& __t,
1411 const tuple<_UElements...>& __u)
1412 {
1413 static_assert(sizeof...(_TElements) == sizeof...(_UElements),
1414 "tuple objects can only be compared if they have equal sizes.");
1415 using __compare = __tuple_compare<tuple<_TElements...>,
1416 tuple<_UElements...>,
1417 0, sizeof...(_TElements)>;
1418 return __compare::__eq(__t, __u);
1419 }
1420
1421#if __cpp_lib_three_way_comparison
1422 template<typename _Cat, typename _Tp, typename _Up>
1423 constexpr _Cat
1424 __tuple_cmp(const _Tp&, const _Up&, index_sequence<>)
1425 { return _Cat::equivalent; }
1426
1427 template<typename _Cat, typename _Tp, typename _Up,
1428 size_t _Idx0, size_t... _Idxs>
1429 constexpr _Cat
1430 __tuple_cmp(const _Tp& __t, const _Up& __u,
1431 index_sequence<_Idx0, _Idxs...>)
1432 {
1433 auto __c
1434 = __detail::__synth3way(std::get<_Idx0>(__t), std::get<_Idx0>(__u));
1435 if (__c != 0)
1436 return __c;
1437 return std::__tuple_cmp<_Cat>(__t, __u, index_sequence<_Idxs...>());
1438 }
1439
1440 template<typename... _Tps, typename... _Ups>
1441 constexpr
1442 common_comparison_category_t<__detail::__synth3way_t<_Tps, _Ups>...>
1443 operator<=>(const tuple<_Tps...>& __t, const tuple<_Ups...>& __u)
1444 {
1445 using _Cat
1446 = common_comparison_category_t<__detail::__synth3way_t<_Tps, _Ups>...>;
1447 return std::__tuple_cmp<_Cat>(__t, __u, index_sequence_for<_Tps...>());
1448 }
1449#else
1450 template<typename... _TElements, typename... _UElements>
1451 constexpr bool
1452 operator<(const tuple<_TElements...>& __t,
1453 const tuple<_UElements...>& __u)
1454 {
1455 static_assert(sizeof...(_TElements) == sizeof...(_UElements),
1456 "tuple objects can only be compared if they have equal sizes.");
1457 using __compare = __tuple_compare<tuple<_TElements...>,
1458 tuple<_UElements...>,
1459 0, sizeof...(_TElements)>;
1460 return __compare::__less(__t, __u);
1461 }
1462
1463 template<typename... _TElements, typename... _UElements>
1464 constexpr bool
1465 operator!=(const tuple<_TElements...>& __t,
1466 const tuple<_UElements...>& __u)
1467 { return !(__t == __u); }
1468
1469 template<typename... _TElements, typename... _UElements>
1470 constexpr bool
1471 operator>(const tuple<_TElements...>& __t,
1472 const tuple<_UElements...>& __u)
1473 { return __u < __t; }
1474
1475 template<typename... _TElements, typename... _UElements>
1476 constexpr bool
1477 operator<=(const tuple<_TElements...>& __t,
1478 const tuple<_UElements...>& __u)
1479 { return !(__u < __t); }
1480
1481 template<typename... _TElements, typename... _UElements>
1482 constexpr bool
1483 operator>=(const tuple<_TElements...>& __t,
1484 const tuple<_UElements...>& __u)
1485 { return !(__t < __u); }
1486#endif // three_way_comparison
1487
1488 // NB: DR 705.
1489 template<typename... _Elements>
1490 constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
1491 make_tuple(_Elements&&... __args)
1492 {
1493 typedef tuple<typename __decay_and_strip<_Elements>::__type...>
1494 __result_type;
1495 return __result_type(std::forward<_Elements>(__args)...);
1496 }
1497
1498 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1499 // 2275. Why is forward_as_tuple not constexpr?
1500 /// std::forward_as_tuple
1501 template<typename... _Elements>
1502 constexpr tuple<_Elements&&...>
1503 forward_as_tuple(_Elements&&... __args) noexcept
1504 { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
1505
1506 template<size_t, typename, typename, size_t>
1507 struct __make_tuple_impl;
1508
1509 template<size_t _Idx, typename _Tuple, typename... _Tp, size_t _Nm>
1510 struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
1511 : __make_tuple_impl<_Idx + 1,
1512 tuple<_Tp..., __tuple_element_t<_Idx, _Tuple>>,
1513 _Tuple, _Nm>
1514 { };
1515
1516 template<std::size_t _Nm, typename _Tuple, typename... _Tp>
1517 struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
1518 {
1519 typedef tuple<_Tp...> __type;
1520 };
1521
1522 template<typename _Tuple>
1523 struct __do_make_tuple
1524 : __make_tuple_impl<0, tuple<>, _Tuple, std::tuple_size<_Tuple>::value>
1525 { };
1526
1527 // Returns the std::tuple equivalent of a tuple-like type.
1528 template<typename _Tuple>
1529 struct __make_tuple
1530 : public __do_make_tuple<__remove_cvref_t<_Tuple>>
1531 { };
1532
1533 // Combines several std::tuple's into a single one.
1534 template<typename...>
1535 struct __combine_tuples;
1536
1537 template<>
1538 struct __combine_tuples<>
1539 {
1540 typedef tuple<> __type;
1541 };
1542
1543 template<typename... _Ts>
1544 struct __combine_tuples<tuple<_Ts...>>
1545 {
1546 typedef tuple<_Ts...> __type;
1547 };
1548
1549 template<typename... _T1s, typename... _T2s, typename... _Rem>
1550 struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
1551 {
1552 typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
1553 _Rem...>::__type __type;
1554 };
1555
1556 // Computes the result type of tuple_cat given a set of tuple-like types.
1557 template<typename... _Tpls>
1558 struct __tuple_cat_result
1559 {
1560 typedef typename __combine_tuples
1561 <typename __make_tuple<_Tpls>::__type...>::__type __type;
1562 };
1563
1564 // Helper to determine the index set for the first tuple-like
1565 // type of a given set.
1566 template<typename...>
1567 struct __make_1st_indices;
1568
1569 template<>
1570 struct __make_1st_indices<>
1571 {
1572 typedef std::_Index_tuple<> __type;
1573 };
1574
1575 template<typename _Tp, typename... _Tpls>
1576 struct __make_1st_indices<_Tp, _Tpls...>
1577 {
1578 typedef typename std::_Build_index_tuple<std::tuple_size<
1579 typename std::remove_reference<_Tp>::type>::value>::__type __type;
1580 };
1581
1582 // Performs the actual concatenation by step-wise expanding tuple-like
1583 // objects into the elements, which are finally forwarded into the
1584 // result tuple.
1585 template<typename _Ret, typename _Indices, typename... _Tpls>
1586 struct __tuple_concater;
1587
1588 template<typename _Ret, std::size_t... _Is, typename _Tp, typename... _Tpls>
1589 struct __tuple_concater<_Ret, std::_Index_tuple<_Is...>, _Tp, _Tpls...>
1590 {
1591 template<typename... _Us>
1592 static constexpr _Ret
1593 _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
1594 {
1595 typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1596 typedef __tuple_concater<_Ret, __idx, _Tpls...> __next;
1597 return __next::_S_do(std::forward<_Tpls>(__tps)...,
1598 std::forward<_Us>(__us)...,
1599 std::get<_Is>(std::forward<_Tp>(__tp))...);
1600 }
1601 };
1602
1603 template<typename _Ret>
1604 struct __tuple_concater<_Ret, std::_Index_tuple<>>
1605 {
1606 template<typename... _Us>
1607 static constexpr _Ret
1608 _S_do(_Us&&... __us)
1609 {
1610 return _Ret(std::forward<_Us>(__us)...);
1611 }
1612 };
1613
1614 /// tuple_cat
1615 template<typename... _Tpls, typename = typename
1616 enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
1617 constexpr auto
1618 tuple_cat(_Tpls&&... __tpls)
1619 -> typename __tuple_cat_result<_Tpls...>::__type
1620 {
1621 typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
1622 typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1623 typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
1624 return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
1625 }
1626
1627 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1628 // 2301. Why is tie not constexpr?
1629 /// tie
1630 template<typename... _Elements>
1631 constexpr tuple<_Elements&...>
1632 tie(_Elements&... __args) noexcept
1633 { return tuple<_Elements&...>(__args...); }
1634
1635 /// swap
1636 template<typename... _Elements>
1637 _GLIBCXX20_CONSTEXPR
1638 inline
1639#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1640 // Constrained free swap overload, see p0185r1
1641 typename enable_if<__and_<__is_swappable<_Elements>...>::value
1642 >::type
1643#else
1644 void
1645#endif
1646 swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
1647 noexcept(noexcept(__x.swap(__y)))
1648 { __x.swap(__y); }
1649
1650#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1651 template<typename... _Elements>
1652 _GLIBCXX20_CONSTEXPR
1653 typename enable_if<!__and_<__is_swappable<_Elements>...>::value>::type
1654 swap(tuple<_Elements...>&, tuple<_Elements...>&) = delete;
1655#endif
1656
1657 // A class (and instance) which can be used in 'tie' when an element
1658 // of a tuple is not required.
1659 // _GLIBCXX14_CONSTEXPR
1660 // 2933. PR for LWG 2773 could be clearer
1661 struct _Swallow_assign
1662 {
1663 template<class _Tp>
1664 _GLIBCXX14_CONSTEXPR const _Swallow_assign&
1665 operator=(const _Tp&) const
1666 { return *this; }
1667 };
1668
1669 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1670 // 2773. Making std::ignore constexpr
1671 _GLIBCXX17_INLINE constexpr _Swallow_assign ignore{};
1672
1673 /// Partial specialization for tuples
1674 template<typename... _Types, typename _Alloc>
1675 struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
1676
1677 // See stl_pair.h...
1678 /** "piecewise construction" using a tuple of arguments for each member.
1679 *
1680 * @param __first Arguments for the first member of the pair.
1681 * @param __second Arguments for the second member of the pair.
1682 *
1683 * The elements of each tuple will be used as the constructor arguments
1684 * for the data members of the pair.
1685 */
1686 template<class _T1, class _T2>
1687 template<typename... _Args1, typename... _Args2>
1688 _GLIBCXX20_CONSTEXPR
1689 inline
1690 pair<_T1, _T2>::
1691 pair(piecewise_construct_t,
1692 tuple<_Args1...> __first, tuple<_Args2...> __second)
1693 : pair(__first, __second,
1694 typename _Build_index_tuple<sizeof...(_Args1)>::__type(),
1695 typename _Build_index_tuple<sizeof...(_Args2)>::__type())
1696 { }
1697
1698 template<class _T1, class _T2>
1699 template<typename... _Args1, std::size_t... _Indexes1,
1700 typename... _Args2, std::size_t... _Indexes2>
1701 _GLIBCXX20_CONSTEXPR inline
1702 pair<_T1, _T2>::
1703 pair(tuple<_Args1...>& __tuple1, tuple<_Args2...>& __tuple2,
1704 _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>)
1705 : first(std::forward<_Args1>(std::get<_Indexes1>(__tuple1))...),
1706 second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
1707 { }
1708
1709#if __cplusplus >= 201703L
1710
1711 // Unpack a std::tuple into a type trait and use its value.
1712 // For cv std::tuple<_Up> the result is _Trait<_Tp, cv _Up...>::value.
1713 // For cv std::tuple<_Up>& the result is _Trait<_Tp, cv _Up&...>::value.
1714 // Otherwise the result is false (because we don't know if std::get throws).
1715 template<template<typename...> class _Trait, typename _Tp, typename _Tuple>
1716 inline constexpr bool __unpack_std_tuple = false;
1717
1718 template<template<typename...> class _Trait, typename _Tp, typename... _Up>
1719 inline constexpr bool __unpack_std_tuple<_Trait, _Tp, tuple<_Up...>>
1720 = _Trait<_Tp, _Up...>::value;
1721
1722 template<template<typename...> class _Trait, typename _Tp, typename... _Up>
1723 inline constexpr bool __unpack_std_tuple<_Trait, _Tp, tuple<_Up...>&>
1724 = _Trait<_Tp, _Up&...>::value;
1725
1726 template<template<typename...> class _Trait, typename _Tp, typename... _Up>
1727 inline constexpr bool __unpack_std_tuple<_Trait, _Tp, const tuple<_Up...>>
1728 = _Trait<_Tp, const _Up...>::value;
1729
1730 template<template<typename...> class _Trait, typename _Tp, typename... _Up>
1731 inline constexpr bool __unpack_std_tuple<_Trait, _Tp, const tuple<_Up...>&>
1732 = _Trait<_Tp, const _Up&...>::value;
1733
1734# define __cpp_lib_apply 201603
1735
1736 template <typename _Fn, typename _Tuple, size_t... _Idx>
1737 constexpr decltype(auto)
1738 __apply_impl(_Fn&& __f, _Tuple&& __t, index_sequence<_Idx...>)
1739 {
1740 return std::__invoke(std::forward<_Fn>(__f),
1741 std::get<_Idx>(std::forward<_Tuple>(__t))...);
1742 }
1743
1744 template <typename _Fn, typename _Tuple>
1745 constexpr decltype(auto)
1746 apply(_Fn&& __f, _Tuple&& __t)
1747 noexcept(__unpack_std_tuple<is_nothrow_invocable, _Fn, _Tuple>)
1748 {
1749 using _Indices
1750 = make_index_sequence<tuple_size_v<remove_reference_t<_Tuple>>>;
1751 return std::__apply_impl(std::forward<_Fn>(__f),
1752 std::forward<_Tuple>(__t),
1753 _Indices{});
1754 }
1755
1756#define __cpp_lib_make_from_tuple 201606
1757
1758 template <typename _Tp, typename _Tuple, size_t... _Idx>
1759 constexpr _Tp
1760 __make_from_tuple_impl(_Tuple&& __t, index_sequence<_Idx...>)
1761 { return _Tp(std::get<_Idx>(std::forward<_Tuple>(__t))...); }
1762
1763 template <typename _Tp, typename _Tuple>
1764 constexpr _Tp
1765 make_from_tuple(_Tuple&& __t)
1766 noexcept(__unpack_std_tuple<is_nothrow_constructible, _Tp, _Tuple>)
1767 {
1768 return __make_from_tuple_impl<_Tp>(
1769 std::forward<_Tuple>(__t),
1770 make_index_sequence<tuple_size_v<remove_reference_t<_Tuple>>>{});
1771 }
1772#endif // C++17
1773
1774 /// @}
1775
1776_GLIBCXX_END_NAMESPACE_VERSION
1777} // namespace std
1778
1779#endif // C++11
1780
1781#endif // _GLIBCXX_TUPLE