libstdc++
type_traits
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1 // C++11 <type_traits> -*- C++ -*-
2 
3 // Copyright (C) 2007-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file include/type_traits
26  * This is a Standard C++ Library header.
27  */
28 
29 #ifndef _GLIBCXX_TYPE_TRAITS
30 #define _GLIBCXX_TYPE_TRAITS 1
31 
32 #pragma GCC system_header
33 
34 #if __cplusplus < 201103L
35 # include <bits/c++0x_warning.h>
36 #else
37 
38 #include <bits/c++config.h>
39 
40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44  template<typename... _Elements>
45  class tuple;
46 
47  template<typename _Tp>
48  class reference_wrapper;
49 
50  /**
51  * @defgroup metaprogramming Metaprogramming
52  * @ingroup utilities
53  *
54  * Template utilities for compile-time introspection and modification,
55  * including type classification traits, type property inspection traits
56  * and type transformation traits.
57  *
58  * @since C++11
59  *
60  * @{
61  */
62 
63  /// integral_constant
64  template<typename _Tp, _Tp __v>
65  struct integral_constant
66  {
67  static constexpr _Tp value = __v;
68  typedef _Tp value_type;
69  typedef integral_constant<_Tp, __v> type;
70  constexpr operator value_type() const noexcept { return value; }
71 #if __cplusplus > 201103L
72 
73 #define __cpp_lib_integral_constant_callable 201304
74 
75  constexpr value_type operator()() const noexcept { return value; }
76 #endif
77  };
78 
79  template<typename _Tp, _Tp __v>
80  constexpr _Tp integral_constant<_Tp, __v>::value;
81 
82  /// The type used as a compile-time boolean with true value.
83  using true_type = integral_constant<bool, true>;
84 
85  /// The type used as a compile-time boolean with false value.
86  using false_type = integral_constant<bool, false>;
87 
88  /// @cond undocumented
89  /// bool_constant for C++11
90  template<bool __v>
91  using __bool_constant = integral_constant<bool, __v>;
92  /// @endcond
93 
94 #if __cplusplus >= 201703L
95 # define __cpp_lib_bool_constant 201505
96  /// Alias template for compile-time boolean constant types.
97  /// @since C++17
98  template<bool __v>
99  using bool_constant = integral_constant<bool, __v>;
100 #endif
101 
102  // Metaprogramming helper types.
103 
104  template<bool, typename, typename>
105  struct conditional;
106 
107  /// @cond undocumented
108  template <typename _Type>
109  struct __type_identity
110  { using type = _Type; };
111 
112  template<typename _Tp>
113  using __type_identity_t = typename __type_identity<_Tp>::type;
114 
115  template<typename...>
116  struct __or_;
117 
118  template<>
119  struct __or_<>
120  : public false_type
121  { };
122 
123  template<typename _B1>
124  struct __or_<_B1>
125  : public _B1
126  { };
127 
128  template<typename _B1, typename _B2>
129  struct __or_<_B1, _B2>
130  : public conditional<_B1::value, _B1, _B2>::type
131  { };
132 
133  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
134  struct __or_<_B1, _B2, _B3, _Bn...>
135  : public conditional<_B1::value, _B1, __or_<_B2, _B3, _Bn...>>::type
136  { };
137 
138  template<typename...>
139  struct __and_;
140 
141  template<>
142  struct __and_<>
143  : public true_type
144  { };
145 
146  template<typename _B1>
147  struct __and_<_B1>
148  : public _B1
149  { };
150 
151  template<typename _B1, typename _B2>
152  struct __and_<_B1, _B2>
153  : public conditional<_B1::value, _B2, _B1>::type
154  { };
155 
156  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
157  struct __and_<_B1, _B2, _B3, _Bn...>
158  : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type
159  { };
160 
161  template<typename _Pp>
162  struct __not_
163  : public __bool_constant<!bool(_Pp::value)>
164  { };
165  /// @endcond
166 
167 #if __cplusplus >= 201703L
168 
169  /// @cond undocumented
170  template<typename... _Bn>
171  inline constexpr bool __or_v = __or_<_Bn...>::value;
172  template<typename... _Bn>
173  inline constexpr bool __and_v = __and_<_Bn...>::value;
174  /// @endcond
175 
176 #define __cpp_lib_logical_traits 201510
177 
178  template<typename... _Bn>
179  struct conjunction
180  : __and_<_Bn...>
181  { };
182 
183  template<typename... _Bn>
184  struct disjunction
185  : __or_<_Bn...>
186  { };
187 
188  template<typename _Pp>
189  struct negation
190  : __not_<_Pp>
191  { };
192 
193  /** @ingroup variable_templates
194  * @{
195  */
196  template<typename... _Bn>
197  inline constexpr bool conjunction_v = conjunction<_Bn...>::value;
198 
199  template<typename... _Bn>
200  inline constexpr bool disjunction_v = disjunction<_Bn...>::value;
201 
202  template<typename _Pp>
203  inline constexpr bool negation_v = negation<_Pp>::value;
204  /// @}
205 
206 #endif // C++17
207 
208  // Forward declarations
209  template<typename>
210  struct is_reference;
211  template<typename>
212  struct is_function;
213  template<typename>
214  struct is_void;
215  template<typename>
216  struct remove_cv;
217  template<typename>
218  struct is_const;
219 
220  /// @cond undocumented
221  template<typename>
222  struct __is_array_unknown_bounds;
223 
224  // Helper functions that return false_type for incomplete classes,
225  // incomplete unions and arrays of known bound from those.
226 
227  template <typename _Tp, size_t = sizeof(_Tp)>
228  constexpr true_type __is_complete_or_unbounded(__type_identity<_Tp>)
229  { return {}; }
230 
231  template <typename _TypeIdentity,
232  typename _NestedType = typename _TypeIdentity::type>
233  constexpr typename __or_<
234  is_reference<_NestedType>,
235  is_function<_NestedType>,
236  is_void<_NestedType>,
237  __is_array_unknown_bounds<_NestedType>
238  >::type __is_complete_or_unbounded(_TypeIdentity)
239  { return {}; }
240 
241  // For several sfinae-friendly trait implementations we transport both the
242  // result information (as the member type) and the failure information (no
243  // member type). This is very similar to std::enable_if, but we cannot use
244  // them, because we need to derive from them as an implementation detail.
245 
246  template<typename _Tp>
247  struct __success_type
248  { typedef _Tp type; };
249 
250  struct __failure_type
251  { };
252 
253  // __remove_cv_t (std::remove_cv_t for C++11).
254  template<typename _Tp>
255  using __remove_cv_t = typename remove_cv<_Tp>::type;
256 
257  // Primary type categories.
258 
259  template<typename>
260  struct __is_void_helper
261  : public false_type { };
262 
263  template<>
264  struct __is_void_helper<void>
265  : public true_type { };
266  /// @endcond
267 
268  /// is_void
269  template<typename _Tp>
270  struct is_void
271  : public __is_void_helper<__remove_cv_t<_Tp>>::type
272  { };
273 
274  /// @cond undocumented
275  template<typename>
276  struct __is_integral_helper
277  : public false_type { };
278 
279  template<>
280  struct __is_integral_helper<bool>
281  : public true_type { };
282 
283  template<>
284  struct __is_integral_helper<char>
285  : public true_type { };
286 
287  template<>
288  struct __is_integral_helper<signed char>
289  : public true_type { };
290 
291  template<>
292  struct __is_integral_helper<unsigned char>
293  : public true_type { };
294 
295  // We want is_integral<wchar_t> to be true (and make_signed/unsigned to work)
296  // even when libc doesn't provide working <wchar.h> and related functions,
297  // so check __WCHAR_TYPE__ instead of _GLIBCXX_USE_WCHAR_T.
298 #ifdef __WCHAR_TYPE__
299  template<>
300  struct __is_integral_helper<wchar_t>
301  : public true_type { };
302 #endif
303 
304 #ifdef _GLIBCXX_USE_CHAR8_T
305  template<>
306  struct __is_integral_helper<char8_t>
307  : public true_type { };
308 #endif
309 
310  template<>
311  struct __is_integral_helper<char16_t>
312  : public true_type { };
313 
314  template<>
315  struct __is_integral_helper<char32_t>
316  : public true_type { };
317 
318  template<>
319  struct __is_integral_helper<short>
320  : public true_type { };
321 
322  template<>
323  struct __is_integral_helper<unsigned short>
324  : public true_type { };
325 
326  template<>
327  struct __is_integral_helper<int>
328  : public true_type { };
329 
330  template<>
331  struct __is_integral_helper<unsigned int>
332  : public true_type { };
333 
334  template<>
335  struct __is_integral_helper<long>
336  : public true_type { };
337 
338  template<>
339  struct __is_integral_helper<unsigned long>
340  : public true_type { };
341 
342  template<>
343  struct __is_integral_helper<long long>
344  : public true_type { };
345 
346  template<>
347  struct __is_integral_helper<unsigned long long>
348  : public true_type { };
349 
350  // Conditionalizing on __STRICT_ANSI__ here will break any port that
351  // uses one of these types for size_t.
352 #if defined(__GLIBCXX_TYPE_INT_N_0)
353  template<>
354  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_0>
355  : public true_type { };
356 
357  template<>
358  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_0>
359  : public true_type { };
360 #endif
361 #if defined(__GLIBCXX_TYPE_INT_N_1)
362  template<>
363  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_1>
364  : public true_type { };
365 
366  template<>
367  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_1>
368  : public true_type { };
369 #endif
370 #if defined(__GLIBCXX_TYPE_INT_N_2)
371  template<>
372  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_2>
373  : public true_type { };
374 
375  template<>
376  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_2>
377  : public true_type { };
378 #endif
379 #if defined(__GLIBCXX_TYPE_INT_N_3)
380  template<>
381  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_3>
382  : public true_type { };
383 
384  template<>
385  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_3>
386  : public true_type { };
387 #endif
388  /// @endcond
389 
390  /// is_integral
391  template<typename _Tp>
392  struct is_integral
393  : public __is_integral_helper<__remove_cv_t<_Tp>>::type
394  { };
395 
396  /// @cond undocumented
397  template<typename>
398  struct __is_floating_point_helper
399  : public false_type { };
400 
401  template<>
402  struct __is_floating_point_helper<float>
403  : public true_type { };
404 
405  template<>
406  struct __is_floating_point_helper<double>
407  : public true_type { };
408 
409  template<>
410  struct __is_floating_point_helper<long double>
411  : public true_type { };
412 
413 #if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
414  template<>
415  struct __is_floating_point_helper<__float128>
416  : public true_type { };
417 #endif
418  /// @endcond
419 
420  /// is_floating_point
421  template<typename _Tp>
422  struct is_floating_point
423  : public __is_floating_point_helper<__remove_cv_t<_Tp>>::type
424  { };
425 
426  /// is_array
427  template<typename>
428  struct is_array
429  : public false_type { };
430 
431  template<typename _Tp, std::size_t _Size>
432  struct is_array<_Tp[_Size]>
433  : public true_type { };
434 
435  template<typename _Tp>
436  struct is_array<_Tp[]>
437  : public true_type { };
438 
439  template<typename>
440  struct __is_pointer_helper
441  : public false_type { };
442 
443  template<typename _Tp>
444  struct __is_pointer_helper<_Tp*>
445  : public true_type { };
446 
447  /// is_pointer
448  template<typename _Tp>
449  struct is_pointer
450  : public __is_pointer_helper<__remove_cv_t<_Tp>>::type
451  { };
452 
453  /// is_lvalue_reference
454  template<typename>
455  struct is_lvalue_reference
456  : public false_type { };
457 
458  template<typename _Tp>
459  struct is_lvalue_reference<_Tp&>
460  : public true_type { };
461 
462  /// is_rvalue_reference
463  template<typename>
464  struct is_rvalue_reference
465  : public false_type { };
466 
467  template<typename _Tp>
468  struct is_rvalue_reference<_Tp&&>
469  : public true_type { };
470 
471  template<typename>
472  struct __is_member_object_pointer_helper
473  : public false_type { };
474 
475  template<typename _Tp, typename _Cp>
476  struct __is_member_object_pointer_helper<_Tp _Cp::*>
477  : public __not_<is_function<_Tp>>::type { };
478 
479  /// is_member_object_pointer
480  template<typename _Tp>
481  struct is_member_object_pointer
482  : public __is_member_object_pointer_helper<__remove_cv_t<_Tp>>::type
483  { };
484 
485  template<typename>
486  struct __is_member_function_pointer_helper
487  : public false_type { };
488 
489  template<typename _Tp, typename _Cp>
490  struct __is_member_function_pointer_helper<_Tp _Cp::*>
491  : public is_function<_Tp>::type { };
492 
493  /// is_member_function_pointer
494  template<typename _Tp>
495  struct is_member_function_pointer
496  : public __is_member_function_pointer_helper<__remove_cv_t<_Tp>>::type
497  { };
498 
499  /// is_enum
500  template<typename _Tp>
501  struct is_enum
502  : public integral_constant<bool, __is_enum(_Tp)>
503  { };
504 
505  /// is_union
506  template<typename _Tp>
507  struct is_union
508  : public integral_constant<bool, __is_union(_Tp)>
509  { };
510 
511  /// is_class
512  template<typename _Tp>
513  struct is_class
514  : public integral_constant<bool, __is_class(_Tp)>
515  { };
516 
517  /// is_function
518  template<typename _Tp>
519  struct is_function
520  : public __bool_constant<!is_const<const _Tp>::value> { };
521 
522  template<typename _Tp>
523  struct is_function<_Tp&>
524  : public false_type { };
525 
526  template<typename _Tp>
527  struct is_function<_Tp&&>
528  : public false_type { };
529 
530 #define __cpp_lib_is_null_pointer 201309
531 
532  template<typename>
533  struct __is_null_pointer_helper
534  : public false_type { };
535 
536  template<>
537  struct __is_null_pointer_helper<std::nullptr_t>
538  : public true_type { };
539 
540  /// is_null_pointer (LWG 2247).
541  template<typename _Tp>
542  struct is_null_pointer
543  : public __is_null_pointer_helper<__remove_cv_t<_Tp>>::type
544  { };
545 
546  /// __is_nullptr_t (deprecated extension).
547  /// @deprecated Use `is_null_pointer` instead.
548  template<typename _Tp>
549  struct __is_nullptr_t
550  : public is_null_pointer<_Tp>
551  { } _GLIBCXX_DEPRECATED_SUGGEST("std::is_null_pointer");
552 
553  // Composite type categories.
554 
555  /// is_reference
556  template<typename _Tp>
557  struct is_reference
558  : public __or_<is_lvalue_reference<_Tp>,
559  is_rvalue_reference<_Tp>>::type
560  { };
561 
562  /// is_arithmetic
563  template<typename _Tp>
564  struct is_arithmetic
565  : public __or_<is_integral<_Tp>, is_floating_point<_Tp>>::type
566  { };
567 
568  /// is_fundamental
569  template<typename _Tp>
570  struct is_fundamental
571  : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
572  is_null_pointer<_Tp>>::type
573  { };
574 
575  /// is_object
576  template<typename _Tp>
577  struct is_object
578  : public __not_<__or_<is_function<_Tp>, is_reference<_Tp>,
579  is_void<_Tp>>>::type
580  { };
581 
582  template<typename>
583  struct is_member_pointer;
584 
585  /// is_scalar
586  template<typename _Tp>
587  struct is_scalar
588  : public __or_<is_arithmetic<_Tp>, is_enum<_Tp>, is_pointer<_Tp>,
589  is_member_pointer<_Tp>, is_null_pointer<_Tp>>::type
590  { };
591 
592  /// is_compound
593  template<typename _Tp>
594  struct is_compound
595  : public __not_<is_fundamental<_Tp>>::type { };
596 
597  /// @cond undocumented
598  template<typename _Tp>
599  struct __is_member_pointer_helper
600  : public false_type { };
601 
602  template<typename _Tp, typename _Cp>
603  struct __is_member_pointer_helper<_Tp _Cp::*>
604  : public true_type { };
605  /// @endcond
606 
607  /// is_member_pointer
608  template<typename _Tp>
609  struct is_member_pointer
610  : public __is_member_pointer_helper<__remove_cv_t<_Tp>>::type
611  { };
612 
613  template<typename, typename>
614  struct is_same;
615 
616  /// @cond undocumented
617  template<typename _Tp, typename... _Types>
618  using __is_one_of = __or_<is_same<_Tp, _Types>...>;
619 
620  // Check if a type is one of the signed integer types.
621  template<typename _Tp>
622  using __is_signed_integer = __is_one_of<__remove_cv_t<_Tp>,
623  signed char, signed short, signed int, signed long,
624  signed long long
625 #if defined(__GLIBCXX_TYPE_INT_N_0)
626  , signed __GLIBCXX_TYPE_INT_N_0
627 #endif
628 #if defined(__GLIBCXX_TYPE_INT_N_1)
629  , signed __GLIBCXX_TYPE_INT_N_1
630 #endif
631 #if defined(__GLIBCXX_TYPE_INT_N_2)
632  , signed __GLIBCXX_TYPE_INT_N_2
633 #endif
634 #if defined(__GLIBCXX_TYPE_INT_N_3)
635  , signed __GLIBCXX_TYPE_INT_N_3
636 #endif
637  >;
638 
639  // Check if a type is one of the unsigned integer types.
640  template<typename _Tp>
641  using __is_unsigned_integer = __is_one_of<__remove_cv_t<_Tp>,
642  unsigned char, unsigned short, unsigned int, unsigned long,
643  unsigned long long
644 #if defined(__GLIBCXX_TYPE_INT_N_0)
645  , unsigned __GLIBCXX_TYPE_INT_N_0
646 #endif
647 #if defined(__GLIBCXX_TYPE_INT_N_1)
648  , unsigned __GLIBCXX_TYPE_INT_N_1
649 #endif
650 #if defined(__GLIBCXX_TYPE_INT_N_2)
651  , unsigned __GLIBCXX_TYPE_INT_N_2
652 #endif
653 #if defined(__GLIBCXX_TYPE_INT_N_3)
654  , unsigned __GLIBCXX_TYPE_INT_N_3
655 #endif
656  >;
657 
658  // Check if a type is one of the signed or unsigned integer types.
659  template<typename _Tp>
660  using __is_standard_integer
661  = __or_<__is_signed_integer<_Tp>, __is_unsigned_integer<_Tp>>;
662 
663  // __void_t (std::void_t for C++11)
664  template<typename...> using __void_t = void;
665 
666  // Utility to detect referenceable types ([defns.referenceable]).
667 
668  template<typename _Tp, typename = void>
669  struct __is_referenceable
670  : public false_type
671  { };
672 
673  template<typename _Tp>
674  struct __is_referenceable<_Tp, __void_t<_Tp&>>
675  : public true_type
676  { };
677  /// @endcond
678 
679  // Type properties.
680 
681  /// is_const
682  template<typename>
683  struct is_const
684  : public false_type { };
685 
686  template<typename _Tp>
687  struct is_const<_Tp const>
688  : public true_type { };
689 
690  /// is_volatile
691  template<typename>
692  struct is_volatile
693  : public false_type { };
694 
695  template<typename _Tp>
696  struct is_volatile<_Tp volatile>
697  : public true_type { };
698 
699  /// is_trivial
700  template<typename _Tp>
701  struct is_trivial
702  : public integral_constant<bool, __is_trivial(_Tp)>
703  {
704  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
705  "template argument must be a complete class or an unbounded array");
706  };
707 
708  /// is_trivially_copyable
709  template<typename _Tp>
710  struct is_trivially_copyable
711  : public integral_constant<bool, __is_trivially_copyable(_Tp)>
712  {
713  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
714  "template argument must be a complete class or an unbounded array");
715  };
716 
717  /// is_standard_layout
718  template<typename _Tp>
719  struct is_standard_layout
720  : public integral_constant<bool, __is_standard_layout(_Tp)>
721  {
722  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
723  "template argument must be a complete class or an unbounded array");
724  };
725 
726  /** is_pod (deprecated in C++20)
727  * @deprecated Use `is_standard_layout && is_trivial` instead.
728  */
729  // Could use is_standard_layout && is_trivial instead of the builtin.
730  template<typename _Tp>
731  struct
732  _GLIBCXX20_DEPRECATED("use is_standard_layout && is_trivial instead")
733  is_pod
734  : public integral_constant<bool, __is_pod(_Tp)>
735  {
736  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
737  "template argument must be a complete class or an unbounded array");
738  };
739 
740  /** is_literal_type
741  * @deprecated Deprecated in C++20. The idea of a literal type isn't useful.
742  */
743  template<typename _Tp>
744  struct
745  _GLIBCXX17_DEPRECATED
746  is_literal_type
747  : public integral_constant<bool, __is_literal_type(_Tp)>
748  {
749  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
750  "template argument must be a complete class or an unbounded array");
751  };
752 
753  /// is_empty
754  template<typename _Tp>
755  struct is_empty
756  : public integral_constant<bool, __is_empty(_Tp)>
757  { };
758 
759  /// is_polymorphic
760  template<typename _Tp>
761  struct is_polymorphic
762  : public integral_constant<bool, __is_polymorphic(_Tp)>
763  { };
764 
765 #if __cplusplus >= 201402L
766 #define __cpp_lib_is_final 201402L
767  /// is_final
768  /// @since C++14
769  template<typename _Tp>
770  struct is_final
771  : public integral_constant<bool, __is_final(_Tp)>
772  { };
773 #endif
774 
775  /// is_abstract
776  template<typename _Tp>
777  struct is_abstract
778  : public integral_constant<bool, __is_abstract(_Tp)>
779  { };
780 
781  /// @cond undocumented
782  template<typename _Tp,
783  bool = is_arithmetic<_Tp>::value>
784  struct __is_signed_helper
785  : public false_type { };
786 
787  template<typename _Tp>
788  struct __is_signed_helper<_Tp, true>
789  : public integral_constant<bool, _Tp(-1) < _Tp(0)>
790  { };
791  /// @endcond
792 
793  /// is_signed
794  template<typename _Tp>
795  struct is_signed
796  : public __is_signed_helper<_Tp>::type
797  { };
798 
799  /// is_unsigned
800  template<typename _Tp>
801  struct is_unsigned
802  : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>
803  { };
804 
805  /// @cond undocumented
806  template<typename _Tp, typename _Up = _Tp&&>
807  _Up
808  __declval(int);
809 
810  template<typename _Tp>
811  _Tp
812  __declval(long);
813  /// @endcond
814 
815  template<typename _Tp>
816  auto declval() noexcept -> decltype(__declval<_Tp>(0));
817 
818  template<typename, unsigned = 0>
819  struct extent;
820 
821  template<typename>
822  struct remove_all_extents;
823 
824  /// @cond undocumented
825  template<typename _Tp>
826  struct __is_array_known_bounds
827  : public integral_constant<bool, (extent<_Tp>::value > 0)>
828  { };
829 
830  template<typename _Tp>
831  struct __is_array_unknown_bounds
832  : public __and_<is_array<_Tp>, __not_<extent<_Tp>>>
833  { };
834 
835  // Destructible and constructible type properties.
836 
837  // In N3290 is_destructible does not say anything about function
838  // types and abstract types, see LWG 2049. This implementation
839  // describes function types as non-destructible and all complete
840  // object types as destructible, iff the explicit destructor
841  // call expression is wellformed.
842  struct __do_is_destructible_impl
843  {
844  template<typename _Tp, typename = decltype(declval<_Tp&>().~_Tp())>
845  static true_type __test(int);
846 
847  template<typename>
848  static false_type __test(...);
849  };
850 
851  template<typename _Tp>
852  struct __is_destructible_impl
853  : public __do_is_destructible_impl
854  {
855  typedef decltype(__test<_Tp>(0)) type;
856  };
857 
858  template<typename _Tp,
859  bool = __or_<is_void<_Tp>,
860  __is_array_unknown_bounds<_Tp>,
861  is_function<_Tp>>::value,
862  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
863  struct __is_destructible_safe;
864 
865  template<typename _Tp>
866  struct __is_destructible_safe<_Tp, false, false>
867  : public __is_destructible_impl<typename
868  remove_all_extents<_Tp>::type>::type
869  { };
870 
871  template<typename _Tp>
872  struct __is_destructible_safe<_Tp, true, false>
873  : public false_type { };
874 
875  template<typename _Tp>
876  struct __is_destructible_safe<_Tp, false, true>
877  : public true_type { };
878  /// @endcond
879 
880  /// is_destructible
881  template<typename _Tp>
882  struct is_destructible
883  : public __is_destructible_safe<_Tp>::type
884  {
885  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
886  "template argument must be a complete class or an unbounded array");
887  };
888 
889  /// @cond undocumented
890 
891  // is_nothrow_destructible requires that is_destructible is
892  // satisfied as well. We realize that by mimicing the
893  // implementation of is_destructible but refer to noexcept(expr)
894  // instead of decltype(expr).
895  struct __do_is_nt_destructible_impl
896  {
897  template<typename _Tp>
898  static __bool_constant<noexcept(declval<_Tp&>().~_Tp())>
899  __test(int);
900 
901  template<typename>
902  static false_type __test(...);
903  };
904 
905  template<typename _Tp>
906  struct __is_nt_destructible_impl
907  : public __do_is_nt_destructible_impl
908  {
909  typedef decltype(__test<_Tp>(0)) type;
910  };
911 
912  template<typename _Tp,
913  bool = __or_<is_void<_Tp>,
914  __is_array_unknown_bounds<_Tp>,
915  is_function<_Tp>>::value,
916  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
917  struct __is_nt_destructible_safe;
918 
919  template<typename _Tp>
920  struct __is_nt_destructible_safe<_Tp, false, false>
921  : public __is_nt_destructible_impl<typename
922  remove_all_extents<_Tp>::type>::type
923  { };
924 
925  template<typename _Tp>
926  struct __is_nt_destructible_safe<_Tp, true, false>
927  : public false_type { };
928 
929  template<typename _Tp>
930  struct __is_nt_destructible_safe<_Tp, false, true>
931  : public true_type { };
932  /// @endcond
933 
934  /// is_nothrow_destructible
935  template<typename _Tp>
936  struct is_nothrow_destructible
937  : public __is_nt_destructible_safe<_Tp>::type
938  {
939  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
940  "template argument must be a complete class or an unbounded array");
941  };
942 
943  /// @cond undocumented
944  template<typename _Tp, typename... _Args>
945  struct __is_constructible_impl
946  : public __bool_constant<__is_constructible(_Tp, _Args...)>
947  { };
948  /// @endcond
949 
950  /// is_constructible
951  template<typename _Tp, typename... _Args>
952  struct is_constructible
953  : public __is_constructible_impl<_Tp, _Args...>
954  {
955  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
956  "template argument must be a complete class or an unbounded array");
957  };
958 
959  /// is_default_constructible
960  template<typename _Tp>
961  struct is_default_constructible
962  : public __is_constructible_impl<_Tp>::type
963  {
964  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
965  "template argument must be a complete class or an unbounded array");
966  };
967 
968  /// @cond undocumented
969  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
970  struct __is_copy_constructible_impl;
971 
972  template<typename _Tp>
973  struct __is_copy_constructible_impl<_Tp, false>
974  : public false_type { };
975 
976  template<typename _Tp>
977  struct __is_copy_constructible_impl<_Tp, true>
978  : public __is_constructible_impl<_Tp, const _Tp&>
979  { };
980  /// @endcond
981 
982  /// is_copy_constructible
983  template<typename _Tp>
984  struct is_copy_constructible
985  : public __is_copy_constructible_impl<_Tp>
986  {
987  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
988  "template argument must be a complete class or an unbounded array");
989  };
990 
991  /// @cond undocumented
992  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
993  struct __is_move_constructible_impl;
994 
995  template<typename _Tp>
996  struct __is_move_constructible_impl<_Tp, false>
997  : public false_type { };
998 
999  template<typename _Tp>
1000  struct __is_move_constructible_impl<_Tp, true>
1001  : public __is_constructible_impl<_Tp, _Tp&&>
1002  { };
1003  /// @endcond
1004 
1005  /// is_move_constructible
1006  template<typename _Tp>
1007  struct is_move_constructible
1008  : public __is_move_constructible_impl<_Tp>
1009  {
1010  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1011  "template argument must be a complete class or an unbounded array");
1012  };
1013 
1014  /// @cond undocumented
1015  template<typename _Tp, typename... _Args>
1016  using __is_nothrow_constructible_impl
1017  = __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
1018  /// @endcond
1019 
1020  /// is_nothrow_constructible
1021  template<typename _Tp, typename... _Args>
1022  struct is_nothrow_constructible
1023  : public __is_nothrow_constructible_impl<_Tp, _Args...>::type
1024  {
1025  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1026  "template argument must be a complete class or an unbounded array");
1027  };
1028 
1029  /// is_nothrow_default_constructible
1030  template<typename _Tp>
1031  struct is_nothrow_default_constructible
1032  : public __bool_constant<__is_nothrow_constructible(_Tp)>
1033  {
1034  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1035  "template argument must be a complete class or an unbounded array");
1036  };
1037 
1038  /// @cond undocumented
1039  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1040  struct __is_nothrow_copy_constructible_impl;
1041 
1042  template<typename _Tp>
1043  struct __is_nothrow_copy_constructible_impl<_Tp, false>
1044  : public false_type { };
1045 
1046  template<typename _Tp>
1047  struct __is_nothrow_copy_constructible_impl<_Tp, true>
1048  : public __is_nothrow_constructible_impl<_Tp, const _Tp&>
1049  { };
1050  /// @endcond
1051 
1052  /// is_nothrow_copy_constructible
1053  template<typename _Tp>
1054  struct is_nothrow_copy_constructible
1055  : public __is_nothrow_copy_constructible_impl<_Tp>::type
1056  {
1057  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1058  "template argument must be a complete class or an unbounded array");
1059  };
1060 
1061  /// @cond undocumented
1062  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1063  struct __is_nothrow_move_constructible_impl;
1064 
1065  template<typename _Tp>
1066  struct __is_nothrow_move_constructible_impl<_Tp, false>
1067  : public false_type { };
1068 
1069  template<typename _Tp>
1070  struct __is_nothrow_move_constructible_impl<_Tp, true>
1071  : public __is_nothrow_constructible_impl<_Tp, _Tp&&>
1072  { };
1073  /// @endcond
1074 
1075  /// is_nothrow_move_constructible
1076  template<typename _Tp>
1077  struct is_nothrow_move_constructible
1078  : public __is_nothrow_move_constructible_impl<_Tp>::type
1079  {
1080  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1081  "template argument must be a complete class or an unbounded array");
1082  };
1083 
1084  /// is_assignable
1085  template<typename _Tp, typename _Up>
1086  struct is_assignable
1087  : public __bool_constant<__is_assignable(_Tp, _Up)>
1088  {
1089  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1090  "template argument must be a complete class or an unbounded array");
1091  };
1092 
1093  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1094  struct __is_copy_assignable_impl;
1095 
1096  template<typename _Tp>
1097  struct __is_copy_assignable_impl<_Tp, false>
1098  : public false_type { };
1099 
1100  template<typename _Tp>
1101  struct __is_copy_assignable_impl<_Tp, true>
1102  : public __bool_constant<__is_assignable(_Tp&, const _Tp&)>
1103  { };
1104 
1105  /// is_copy_assignable
1106  template<typename _Tp>
1107  struct is_copy_assignable
1108  : public __is_copy_assignable_impl<_Tp>::type
1109  {
1110  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1111  "template argument must be a complete class or an unbounded array");
1112  };
1113 
1114  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1115  struct __is_move_assignable_impl;
1116 
1117  template<typename _Tp>
1118  struct __is_move_assignable_impl<_Tp, false>
1119  : public false_type { };
1120 
1121  template<typename _Tp>
1122  struct __is_move_assignable_impl<_Tp, true>
1123  : public __bool_constant<__is_assignable(_Tp&, _Tp&&)>
1124  { };
1125 
1126  /// is_move_assignable
1127  template<typename _Tp>
1128  struct is_move_assignable
1129  : public __is_move_assignable_impl<_Tp>::type
1130  {
1131  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1132  "template argument must be a complete class or an unbounded array");
1133  };
1134 
1135  template<typename _Tp, typename _Up>
1136  using __is_nothrow_assignable_impl
1137  = __bool_constant<__is_nothrow_assignable(_Tp, _Up)>;
1138 
1139  /// is_nothrow_assignable
1140  template<typename _Tp, typename _Up>
1141  struct is_nothrow_assignable
1142  : public __is_nothrow_assignable_impl<_Tp, _Up>
1143  {
1144  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1145  "template argument must be a complete class or an unbounded array");
1146  };
1147 
1148  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1149  struct __is_nt_copy_assignable_impl;
1150 
1151  template<typename _Tp>
1152  struct __is_nt_copy_assignable_impl<_Tp, false>
1153  : public false_type { };
1154 
1155  template<typename _Tp>
1156  struct __is_nt_copy_assignable_impl<_Tp, true>
1157  : public __is_nothrow_assignable_impl<_Tp&, const _Tp&>
1158  { };
1159 
1160  /// is_nothrow_copy_assignable
1161  template<typename _Tp>
1162  struct is_nothrow_copy_assignable
1163  : public __is_nt_copy_assignable_impl<_Tp>
1164  {
1165  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1166  "template argument must be a complete class or an unbounded array");
1167  };
1168 
1169  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1170  struct __is_nt_move_assignable_impl;
1171 
1172  template<typename _Tp>
1173  struct __is_nt_move_assignable_impl<_Tp, false>
1174  : public false_type { };
1175 
1176  template<typename _Tp>
1177  struct __is_nt_move_assignable_impl<_Tp, true>
1178  : public __is_nothrow_assignable_impl<_Tp&, _Tp&&>
1179  { };
1180 
1181  /// is_nothrow_move_assignable
1182  template<typename _Tp>
1183  struct is_nothrow_move_assignable
1184  : public __is_nt_move_assignable_impl<_Tp>
1185  {
1186  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1187  "template argument must be a complete class or an unbounded array");
1188  };
1189 
1190  /// is_trivially_constructible
1191  template<typename _Tp, typename... _Args>
1192  struct is_trivially_constructible
1193  : public __bool_constant<__is_trivially_constructible(_Tp, _Args...)>
1194  {
1195  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1196  "template argument must be a complete class or an unbounded array");
1197  };
1198 
1199  /// is_trivially_default_constructible
1200  template<typename _Tp>
1201  struct is_trivially_default_constructible
1202  : public __bool_constant<__is_trivially_constructible(_Tp)>
1203  {
1204  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1205  "template argument must be a complete class or an unbounded array");
1206  };
1207 
1208  struct __do_is_implicitly_default_constructible_impl
1209  {
1210  template <typename _Tp>
1211  static void __helper(const _Tp&);
1212 
1213  template <typename _Tp>
1214  static true_type __test(const _Tp&,
1215  decltype(__helper<const _Tp&>({}))* = 0);
1216 
1217  static false_type __test(...);
1218  };
1219 
1220  template<typename _Tp>
1221  struct __is_implicitly_default_constructible_impl
1222  : public __do_is_implicitly_default_constructible_impl
1223  {
1224  typedef decltype(__test(declval<_Tp>())) type;
1225  };
1226 
1227  template<typename _Tp>
1228  struct __is_implicitly_default_constructible_safe
1229  : public __is_implicitly_default_constructible_impl<_Tp>::type
1230  { };
1231 
1232  template <typename _Tp>
1233  struct __is_implicitly_default_constructible
1234  : public __and_<__is_constructible_impl<_Tp>,
1235  __is_implicitly_default_constructible_safe<_Tp>>
1236  { };
1237 
1238  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1239  struct __is_trivially_copy_constructible_impl;
1240 
1241  template<typename _Tp>
1242  struct __is_trivially_copy_constructible_impl<_Tp, false>
1243  : public false_type { };
1244 
1245  template<typename _Tp>
1246  struct __is_trivially_copy_constructible_impl<_Tp, true>
1247  : public __and_<__is_copy_constructible_impl<_Tp>,
1248  integral_constant<bool,
1249  __is_trivially_constructible(_Tp, const _Tp&)>>
1250  { };
1251 
1252  /// is_trivially_copy_constructible
1253  template<typename _Tp>
1254  struct is_trivially_copy_constructible
1255  : public __is_trivially_copy_constructible_impl<_Tp>
1256  {
1257  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1258  "template argument must be a complete class or an unbounded array");
1259  };
1260 
1261  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1262  struct __is_trivially_move_constructible_impl;
1263 
1264  template<typename _Tp>
1265  struct __is_trivially_move_constructible_impl<_Tp, false>
1266  : public false_type { };
1267 
1268  template<typename _Tp>
1269  struct __is_trivially_move_constructible_impl<_Tp, true>
1270  : public __and_<__is_move_constructible_impl<_Tp>,
1271  integral_constant<bool,
1272  __is_trivially_constructible(_Tp, _Tp&&)>>
1273  { };
1274 
1275  /// is_trivially_move_constructible
1276  template<typename _Tp>
1277  struct is_trivially_move_constructible
1278  : public __is_trivially_move_constructible_impl<_Tp>
1279  {
1280  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1281  "template argument must be a complete class or an unbounded array");
1282  };
1283 
1284  /// is_trivially_assignable
1285  template<typename _Tp, typename _Up>
1286  struct is_trivially_assignable
1287  : public __bool_constant<__is_trivially_assignable(_Tp, _Up)>
1288  {
1289  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1290  "template argument must be a complete class or an unbounded array");
1291  };
1292 
1293  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1294  struct __is_trivially_copy_assignable_impl;
1295 
1296  template<typename _Tp>
1297  struct __is_trivially_copy_assignable_impl<_Tp, false>
1298  : public false_type { };
1299 
1300  template<typename _Tp>
1301  struct __is_trivially_copy_assignable_impl<_Tp, true>
1302  : public __bool_constant<__is_trivially_assignable(_Tp&, const _Tp&)>
1303  { };
1304 
1305  /// is_trivially_copy_assignable
1306  template<typename _Tp>
1307  struct is_trivially_copy_assignable
1308  : public __is_trivially_copy_assignable_impl<_Tp>
1309  {
1310  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1311  "template argument must be a complete class or an unbounded array");
1312  };
1313 
1314  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1315  struct __is_trivially_move_assignable_impl;
1316 
1317  template<typename _Tp>
1318  struct __is_trivially_move_assignable_impl<_Tp, false>
1319  : public false_type { };
1320 
1321  template<typename _Tp>
1322  struct __is_trivially_move_assignable_impl<_Tp, true>
1323  : public __bool_constant<__is_trivially_assignable(_Tp&, _Tp&&)>
1324  { };
1325 
1326  /// is_trivially_move_assignable
1327  template<typename _Tp>
1328  struct is_trivially_move_assignable
1329  : public __is_trivially_move_assignable_impl<_Tp>
1330  {
1331  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1332  "template argument must be a complete class or an unbounded array");
1333  };
1334 
1335  /// is_trivially_destructible
1336  template<typename _Tp>
1337  struct is_trivially_destructible
1338  : public __and_<__is_destructible_safe<_Tp>,
1339  __bool_constant<__has_trivial_destructor(_Tp)>>
1340  {
1341  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1342  "template argument must be a complete class or an unbounded array");
1343  };
1344 
1345 
1346  /// has_virtual_destructor
1347  template<typename _Tp>
1348  struct has_virtual_destructor
1349  : public integral_constant<bool, __has_virtual_destructor(_Tp)>
1350  {
1351  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1352  "template argument must be a complete class or an unbounded array");
1353  };
1354 
1355 
1356  // type property queries.
1357 
1358  /// alignment_of
1359  template<typename _Tp>
1360  struct alignment_of
1361  : public integral_constant<std::size_t, alignof(_Tp)>
1362  {
1363  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1364  "template argument must be a complete class or an unbounded array");
1365  };
1366 
1367  /// rank
1368  template<typename>
1369  struct rank
1370  : public integral_constant<std::size_t, 0> { };
1371 
1372  template<typename _Tp, std::size_t _Size>
1373  struct rank<_Tp[_Size]>
1374  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1375 
1376  template<typename _Tp>
1377  struct rank<_Tp[]>
1378  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1379 
1380  /// extent
1381  template<typename, unsigned _Uint>
1382  struct extent
1383  : public integral_constant<std::size_t, 0> { };
1384 
1385  template<typename _Tp, unsigned _Uint, std::size_t _Size>
1386  struct extent<_Tp[_Size], _Uint>
1387  : public integral_constant<std::size_t,
1388  _Uint == 0 ? _Size : extent<_Tp,
1389  _Uint - 1>::value>
1390  { };
1391 
1392  template<typename _Tp, unsigned _Uint>
1393  struct extent<_Tp[], _Uint>
1394  : public integral_constant<std::size_t,
1395  _Uint == 0 ? 0 : extent<_Tp,
1396  _Uint - 1>::value>
1397  { };
1398 
1399 
1400  // Type relations.
1401 
1402  /// is_same
1403  template<typename _Tp, typename _Up>
1404  struct is_same
1405 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1406  : public integral_constant<bool, __is_same(_Tp, _Up)>
1407 #else
1408  : public false_type
1409 #endif
1410  { };
1411 
1412 #ifndef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1413  template<typename _Tp>
1414  struct is_same<_Tp, _Tp>
1415  : public true_type
1416  { };
1417 #endif
1418 
1419  /// is_base_of
1420  template<typename _Base, typename _Derived>
1421  struct is_base_of
1422  : public integral_constant<bool, __is_base_of(_Base, _Derived)>
1423  { };
1424 
1425  template<typename _From, typename _To,
1426  bool = __or_<is_void<_From>, is_function<_To>,
1427  is_array<_To>>::value>
1428  struct __is_convertible_helper
1429  {
1430  typedef typename is_void<_To>::type type;
1431  };
1432 
1433 #pragma GCC diagnostic push
1434 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1435  template<typename _From, typename _To>
1436  class __is_convertible_helper<_From, _To, false>
1437  {
1438  template<typename _To1>
1439  static void __test_aux(_To1) noexcept;
1440 
1441  template<typename _From1, typename _To1,
1442  typename = decltype(__test_aux<_To1>(std::declval<_From1>()))>
1443  static true_type
1444  __test(int);
1445 
1446  template<typename, typename>
1447  static false_type
1448  __test(...);
1449 
1450  public:
1451  typedef decltype(__test<_From, _To>(0)) type;
1452  };
1453 #pragma GCC diagnostic pop
1454 
1455  /// is_convertible
1456  template<typename _From, typename _To>
1457  struct is_convertible
1458  : public __is_convertible_helper<_From, _To>::type
1459  { };
1460 
1461  // helper trait for unique_ptr<T[]>, shared_ptr<T[]>, and span<T, N>
1462  template<typename _ToElementType, typename _FromElementType>
1463  using __is_array_convertible
1464  = is_convertible<_FromElementType(*)[], _ToElementType(*)[]>;
1465 
1466  template<typename _From, typename _To,
1467  bool = __or_<is_void<_From>, is_function<_To>,
1468  is_array<_To>>::value>
1469  struct __is_nt_convertible_helper
1470  : is_void<_To>
1471  { };
1472 
1473 #pragma GCC diagnostic push
1474 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1475  template<typename _From, typename _To>
1476  class __is_nt_convertible_helper<_From, _To, false>
1477  {
1478  template<typename _To1>
1479  static void __test_aux(_To1) noexcept;
1480 
1481  template<typename _From1, typename _To1>
1482  static
1483  __bool_constant<noexcept(__test_aux<_To1>(std::declval<_From1>()))>
1484  __test(int);
1485 
1486  template<typename, typename>
1487  static false_type
1488  __test(...);
1489 
1490  public:
1491  using type = decltype(__test<_From, _To>(0));
1492  };
1493 #pragma GCC diagnostic pop
1494 
1495 #if __cplusplus > 201703L
1496 #define __cpp_lib_is_nothrow_convertible 201806L
1497  /// is_nothrow_convertible
1498  template<typename _From, typename _To>
1499  struct is_nothrow_convertible
1500  : public __is_nt_convertible_helper<_From, _To>::type
1501  { };
1502 
1503  /// is_nothrow_convertible_v
1504  template<typename _From, typename _To>
1505  inline constexpr bool is_nothrow_convertible_v
1506  = is_nothrow_convertible<_From, _To>::value;
1507 #endif // C++2a
1508 
1509  // Const-volatile modifications.
1510 
1511  /// remove_const
1512  template<typename _Tp>
1513  struct remove_const
1514  { typedef _Tp type; };
1515 
1516  template<typename _Tp>
1517  struct remove_const<_Tp const>
1518  { typedef _Tp type; };
1519 
1520  /// remove_volatile
1521  template<typename _Tp>
1522  struct remove_volatile
1523  { typedef _Tp type; };
1524 
1525  template<typename _Tp>
1526  struct remove_volatile<_Tp volatile>
1527  { typedef _Tp type; };
1528 
1529  /// remove_cv
1530  template<typename _Tp>
1531  struct remove_cv
1532  { using type = _Tp; };
1533 
1534  template<typename _Tp>
1535  struct remove_cv<const _Tp>
1536  { using type = _Tp; };
1537 
1538  template<typename _Tp>
1539  struct remove_cv<volatile _Tp>
1540  { using type = _Tp; };
1541 
1542  template<typename _Tp>
1543  struct remove_cv<const volatile _Tp>
1544  { using type = _Tp; };
1545 
1546  /// add_const
1547  template<typename _Tp>
1548  struct add_const
1549  { typedef _Tp const type; };
1550 
1551  /// add_volatile
1552  template<typename _Tp>
1553  struct add_volatile
1554  { typedef _Tp volatile type; };
1555 
1556  /// add_cv
1557  template<typename _Tp>
1558  struct add_cv
1559  {
1560  typedef typename
1561  add_const<typename add_volatile<_Tp>::type>::type type;
1562  };
1563 
1564 #if __cplusplus > 201103L
1565 
1566 #define __cpp_lib_transformation_trait_aliases 201304
1567 
1568  /// Alias template for remove_const
1569  template<typename _Tp>
1570  using remove_const_t = typename remove_const<_Tp>::type;
1571 
1572  /// Alias template for remove_volatile
1573  template<typename _Tp>
1574  using remove_volatile_t = typename remove_volatile<_Tp>::type;
1575 
1576  /// Alias template for remove_cv
1577  template<typename _Tp>
1578  using remove_cv_t = typename remove_cv<_Tp>::type;
1579 
1580  /// Alias template for add_const
1581  template<typename _Tp>
1582  using add_const_t = typename add_const<_Tp>::type;
1583 
1584  /// Alias template for add_volatile
1585  template<typename _Tp>
1586  using add_volatile_t = typename add_volatile<_Tp>::type;
1587 
1588  /// Alias template for add_cv
1589  template<typename _Tp>
1590  using add_cv_t = typename add_cv<_Tp>::type;
1591 #endif
1592 
1593  // Reference transformations.
1594 
1595  /// remove_reference
1596  template<typename _Tp>
1597  struct remove_reference
1598  { typedef _Tp type; };
1599 
1600  template<typename _Tp>
1601  struct remove_reference<_Tp&>
1602  { typedef _Tp type; };
1603 
1604  template<typename _Tp>
1605  struct remove_reference<_Tp&&>
1606  { typedef _Tp type; };
1607 
1608  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1609  struct __add_lvalue_reference_helper
1610  { typedef _Tp type; };
1611 
1612  template<typename _Tp>
1613  struct __add_lvalue_reference_helper<_Tp, true>
1614  { typedef _Tp& type; };
1615 
1616  /// add_lvalue_reference
1617  template<typename _Tp>
1618  struct add_lvalue_reference
1619  : public __add_lvalue_reference_helper<_Tp>
1620  { };
1621 
1622  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1623  struct __add_rvalue_reference_helper
1624  { typedef _Tp type; };
1625 
1626  template<typename _Tp>
1627  struct __add_rvalue_reference_helper<_Tp, true>
1628  { typedef _Tp&& type; };
1629 
1630  /// add_rvalue_reference
1631  template<typename _Tp>
1632  struct add_rvalue_reference
1633  : public __add_rvalue_reference_helper<_Tp>
1634  { };
1635 
1636 #if __cplusplus > 201103L
1637  /// Alias template for remove_reference
1638  template<typename _Tp>
1639  using remove_reference_t = typename remove_reference<_Tp>::type;
1640 
1641  /// Alias template for add_lvalue_reference
1642  template<typename _Tp>
1643  using add_lvalue_reference_t = typename add_lvalue_reference<_Tp>::type;
1644 
1645  /// Alias template for add_rvalue_reference
1646  template<typename _Tp>
1647  using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
1648 #endif
1649 
1650  // Sign modifications.
1651 
1652  /// @cond undocumented
1653 
1654  // Utility for constructing identically cv-qualified types.
1655  template<typename _Unqualified, bool _IsConst, bool _IsVol>
1656  struct __cv_selector;
1657 
1658  template<typename _Unqualified>
1659  struct __cv_selector<_Unqualified, false, false>
1660  { typedef _Unqualified __type; };
1661 
1662  template<typename _Unqualified>
1663  struct __cv_selector<_Unqualified, false, true>
1664  { typedef volatile _Unqualified __type; };
1665 
1666  template<typename _Unqualified>
1667  struct __cv_selector<_Unqualified, true, false>
1668  { typedef const _Unqualified __type; };
1669 
1670  template<typename _Unqualified>
1671  struct __cv_selector<_Unqualified, true, true>
1672  { typedef const volatile _Unqualified __type; };
1673 
1674  template<typename _Qualified, typename _Unqualified,
1675  bool _IsConst = is_const<_Qualified>::value,
1676  bool _IsVol = is_volatile<_Qualified>::value>
1677  class __match_cv_qualifiers
1678  {
1679  typedef __cv_selector<_Unqualified, _IsConst, _IsVol> __match;
1680 
1681  public:
1682  typedef typename __match::__type __type;
1683  };
1684 
1685  // Utility for finding the unsigned versions of signed integral types.
1686  template<typename _Tp>
1687  struct __make_unsigned
1688  { typedef _Tp __type; };
1689 
1690  template<>
1691  struct __make_unsigned<char>
1692  { typedef unsigned char __type; };
1693 
1694  template<>
1695  struct __make_unsigned<signed char>
1696  { typedef unsigned char __type; };
1697 
1698  template<>
1699  struct __make_unsigned<short>
1700  { typedef unsigned short __type; };
1701 
1702  template<>
1703  struct __make_unsigned<int>
1704  { typedef unsigned int __type; };
1705 
1706  template<>
1707  struct __make_unsigned<long>
1708  { typedef unsigned long __type; };
1709 
1710  template<>
1711  struct __make_unsigned<long long>
1712  { typedef unsigned long long __type; };
1713 
1714 #if defined(__GLIBCXX_TYPE_INT_N_0)
1715  template<>
1716  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_0>
1717  { typedef unsigned __GLIBCXX_TYPE_INT_N_0 __type; };
1718 #endif
1719 #if defined(__GLIBCXX_TYPE_INT_N_1)
1720  template<>
1721  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_1>
1722  { typedef unsigned __GLIBCXX_TYPE_INT_N_1 __type; };
1723 #endif
1724 #if defined(__GLIBCXX_TYPE_INT_N_2)
1725  template<>
1726  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_2>
1727  { typedef unsigned __GLIBCXX_TYPE_INT_N_2 __type; };
1728 #endif
1729 #if defined(__GLIBCXX_TYPE_INT_N_3)
1730  template<>
1731  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_3>
1732  { typedef unsigned __GLIBCXX_TYPE_INT_N_3 __type; };
1733 #endif
1734 
1735  // Select between integral and enum: not possible to be both.
1736  template<typename _Tp,
1737  bool _IsInt = is_integral<_Tp>::value,
1738  bool _IsEnum = is_enum<_Tp>::value>
1739  class __make_unsigned_selector;
1740 
1741  template<typename _Tp>
1742  class __make_unsigned_selector<_Tp, true, false>
1743  {
1744  using __unsigned_type
1745  = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
1746 
1747  public:
1748  using __type
1749  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1750  };
1751 
1752  class __make_unsigned_selector_base
1753  {
1754  protected:
1755  template<typename...> struct _List { };
1756 
1757  template<typename _Tp, typename... _Up>
1758  struct _List<_Tp, _Up...> : _List<_Up...>
1759  { static constexpr size_t __size = sizeof(_Tp); };
1760 
1761  template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
1762  struct __select;
1763 
1764  template<size_t _Sz, typename _Uint, typename... _UInts>
1765  struct __select<_Sz, _List<_Uint, _UInts...>, true>
1766  { using __type = _Uint; };
1767 
1768  template<size_t _Sz, typename _Uint, typename... _UInts>
1769  struct __select<_Sz, _List<_Uint, _UInts...>, false>
1770  : __select<_Sz, _List<_UInts...>>
1771  { };
1772  };
1773 
1774  // Choose unsigned integer type with the smallest rank and same size as _Tp
1775  template<typename _Tp>
1776  class __make_unsigned_selector<_Tp, false, true>
1777  : __make_unsigned_selector_base
1778  {
1779  // With -fshort-enums, an enum may be as small as a char.
1780  using _UInts = _List<unsigned char, unsigned short, unsigned int,
1781  unsigned long, unsigned long long>;
1782 
1783  using __unsigned_type = typename __select<sizeof(_Tp), _UInts>::__type;
1784 
1785  public:
1786  using __type
1787  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1788  };
1789 
1790  // wchar_t, char8_t, char16_t and char32_t are integral types but are
1791  // neither signed integer types nor unsigned integer types, so must be
1792  // transformed to the unsigned integer type with the smallest rank.
1793  // Use the partial specialization for enumeration types to do that.
1794 #ifdef __WCHAR_TYPE__
1795  template<>
1796  struct __make_unsigned<wchar_t>
1797  {
1798  using __type
1799  = typename __make_unsigned_selector<wchar_t, false, true>::__type;
1800  };
1801 #endif
1802 
1803 #ifdef _GLIBCXX_USE_CHAR8_T
1804  template<>
1805  struct __make_unsigned<char8_t>
1806  {
1807  using __type
1808  = typename __make_unsigned_selector<char8_t, false, true>::__type;
1809  };
1810 #endif
1811 
1812  template<>
1813  struct __make_unsigned<char16_t>
1814  {
1815  using __type
1816  = typename __make_unsigned_selector<char16_t, false, true>::__type;
1817  };
1818 
1819  template<>
1820  struct __make_unsigned<char32_t>
1821  {
1822  using __type
1823  = typename __make_unsigned_selector<char32_t, false, true>::__type;
1824  };
1825  /// @endcond
1826 
1827  // Given an integral/enum type, return the corresponding unsigned
1828  // integer type.
1829  // Primary template.
1830  /// make_unsigned
1831  template<typename _Tp>
1832  struct make_unsigned
1833  { typedef typename __make_unsigned_selector<_Tp>::__type type; };
1834 
1835  // Integral, but don't define.
1836  template<>
1837  struct make_unsigned<bool>;
1838 
1839  /// @cond undocumented
1840 
1841  // Utility for finding the signed versions of unsigned integral types.
1842  template<typename _Tp>
1843  struct __make_signed
1844  { typedef _Tp __type; };
1845 
1846  template<>
1847  struct __make_signed<char>
1848  { typedef signed char __type; };
1849 
1850  template<>
1851  struct __make_signed<unsigned char>
1852  { typedef signed char __type; };
1853 
1854  template<>
1855  struct __make_signed<unsigned short>
1856  { typedef signed short __type; };
1857 
1858  template<>
1859  struct __make_signed<unsigned int>
1860  { typedef signed int __type; };
1861 
1862  template<>
1863  struct __make_signed<unsigned long>
1864  { typedef signed long __type; };
1865 
1866  template<>
1867  struct __make_signed<unsigned long long>
1868  { typedef signed long long __type; };
1869 
1870 #if defined(__GLIBCXX_TYPE_INT_N_0)
1871  template<>
1872  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_0>
1873  { typedef __GLIBCXX_TYPE_INT_N_0 __type; };
1874 #endif
1875 #if defined(__GLIBCXX_TYPE_INT_N_1)
1876  template<>
1877  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_1>
1878  { typedef __GLIBCXX_TYPE_INT_N_1 __type; };
1879 #endif
1880 #if defined(__GLIBCXX_TYPE_INT_N_2)
1881  template<>
1882  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_2>
1883  { typedef __GLIBCXX_TYPE_INT_N_2 __type; };
1884 #endif
1885 #if defined(__GLIBCXX_TYPE_INT_N_3)
1886  template<>
1887  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_3>
1888  { typedef __GLIBCXX_TYPE_INT_N_3 __type; };
1889 #endif
1890 
1891  // Select between integral and enum: not possible to be both.
1892  template<typename _Tp,
1893  bool _IsInt = is_integral<_Tp>::value,
1894  bool _IsEnum = is_enum<_Tp>::value>
1895  class __make_signed_selector;
1896 
1897  template<typename _Tp>
1898  class __make_signed_selector<_Tp, true, false>
1899  {
1900  using __signed_type
1901  = typename __make_signed<__remove_cv_t<_Tp>>::__type;
1902 
1903  public:
1904  using __type
1905  = typename __match_cv_qualifiers<_Tp, __signed_type>::__type;
1906  };
1907 
1908  // Choose signed integer type with the smallest rank and same size as _Tp
1909  template<typename _Tp>
1910  class __make_signed_selector<_Tp, false, true>
1911  {
1912  typedef typename __make_unsigned_selector<_Tp>::__type __unsigned_type;
1913 
1914  public:
1915  typedef typename __make_signed_selector<__unsigned_type>::__type __type;
1916  };
1917 
1918  // wchar_t, char16_t and char32_t are integral types but are neither
1919  // signed integer types nor unsigned integer types, so must be
1920  // transformed to the signed integer type with the smallest rank.
1921  // Use the partial specialization for enumeration types to do that.
1922 #if defined(__WCHAR_TYPE__)
1923  template<>
1924  struct __make_signed<wchar_t>
1925  {
1926  using __type
1927  = typename __make_signed_selector<wchar_t, false, true>::__type;
1928  };
1929 #endif
1930 
1931 #if defined(_GLIBCXX_USE_CHAR8_T)
1932  template<>
1933  struct __make_signed<char8_t>
1934  {
1935  using __type
1936  = typename __make_signed_selector<char8_t, false, true>::__type;
1937  };
1938 #endif
1939 
1940  template<>
1941  struct __make_signed<char16_t>
1942  {
1943  using __type
1944  = typename __make_signed_selector<char16_t, false, true>::__type;
1945  };
1946 
1947  template<>
1948  struct __make_signed<char32_t>
1949  {
1950  using __type
1951  = typename __make_signed_selector<char32_t, false, true>::__type;
1952  };
1953  /// @endcond
1954 
1955  // Given an integral/enum type, return the corresponding signed
1956  // integer type.
1957  // Primary template.
1958  /// make_signed
1959  template<typename _Tp>
1960  struct make_signed
1961  { typedef typename __make_signed_selector<_Tp>::__type type; };
1962 
1963  // Integral, but don't define.
1964  template<>
1965  struct make_signed<bool>;
1966 
1967 #if __cplusplus > 201103L
1968  /// Alias template for make_signed
1969  template<typename _Tp>
1970  using make_signed_t = typename make_signed<_Tp>::type;
1971 
1972  /// Alias template for make_unsigned
1973  template<typename _Tp>
1974  using make_unsigned_t = typename make_unsigned<_Tp>::type;
1975 #endif
1976 
1977  // Array modifications.
1978 
1979  /// remove_extent
1980  template<typename _Tp>
1981  struct remove_extent
1982  { typedef _Tp type; };
1983 
1984  template<typename _Tp, std::size_t _Size>
1985  struct remove_extent<_Tp[_Size]>
1986  { typedef _Tp type; };
1987 
1988  template<typename _Tp>
1989  struct remove_extent<_Tp[]>
1990  { typedef _Tp type; };
1991 
1992  /// remove_all_extents
1993  template<typename _Tp>
1994  struct remove_all_extents
1995  { typedef _Tp type; };
1996 
1997  template<typename _Tp, std::size_t _Size>
1998  struct remove_all_extents<_Tp[_Size]>
1999  { typedef typename remove_all_extents<_Tp>::type type; };
2000 
2001  template<typename _Tp>
2002  struct remove_all_extents<_Tp[]>
2003  { typedef typename remove_all_extents<_Tp>::type type; };
2004 
2005 #if __cplusplus > 201103L
2006  /// Alias template for remove_extent
2007  template<typename _Tp>
2008  using remove_extent_t = typename remove_extent<_Tp>::type;
2009 
2010  /// Alias template for remove_all_extents
2011  template<typename _Tp>
2012  using remove_all_extents_t = typename remove_all_extents<_Tp>::type;
2013 #endif
2014 
2015  // Pointer modifications.
2016 
2017  template<typename _Tp, typename>
2018  struct __remove_pointer_helper
2019  { typedef _Tp type; };
2020 
2021  template<typename _Tp, typename _Up>
2022  struct __remove_pointer_helper<_Tp, _Up*>
2023  { typedef _Up type; };
2024 
2025  /// remove_pointer
2026  template<typename _Tp>
2027  struct remove_pointer
2028  : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
2029  { };
2030 
2031  template<typename _Tp, bool = __or_<__is_referenceable<_Tp>,
2032  is_void<_Tp>>::value>
2033  struct __add_pointer_helper
2034  { typedef _Tp type; };
2035 
2036  template<typename _Tp>
2037  struct __add_pointer_helper<_Tp, true>
2038  { typedef typename remove_reference<_Tp>::type* type; };
2039 
2040  /// add_pointer
2041  template<typename _Tp>
2042  struct add_pointer
2043  : public __add_pointer_helper<_Tp>
2044  { };
2045 
2046 #if __cplusplus > 201103L
2047  /// Alias template for remove_pointer
2048  template<typename _Tp>
2049  using remove_pointer_t = typename remove_pointer<_Tp>::type;
2050 
2051  /// Alias template for add_pointer
2052  template<typename _Tp>
2053  using add_pointer_t = typename add_pointer<_Tp>::type;
2054 #endif
2055 
2056  template<std::size_t _Len>
2057  struct __aligned_storage_msa
2058  {
2059  union __type
2060  {
2061  unsigned char __data[_Len];
2062  struct __attribute__((__aligned__)) { } __align;
2063  };
2064  };
2065 
2066  /**
2067  * @brief Alignment type.
2068  *
2069  * The value of _Align is a default-alignment which shall be the
2070  * most stringent alignment requirement for any C++ object type
2071  * whose size is no greater than _Len (3.9). The member typedef
2072  * type shall be a POD type suitable for use as uninitialized
2073  * storage for any object whose size is at most _Len and whose
2074  * alignment is a divisor of _Align.
2075  */
2076  template<std::size_t _Len, std::size_t _Align =
2077  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2078  struct aligned_storage
2079  {
2080  union type
2081  {
2082  unsigned char __data[_Len];
2083  struct __attribute__((__aligned__((_Align)))) { } __align;
2084  };
2085  };
2086 
2087  template <typename... _Types>
2088  struct __strictest_alignment
2089  {
2090  static const size_t _S_alignment = 0;
2091  static const size_t _S_size = 0;
2092  };
2093 
2094  template <typename _Tp, typename... _Types>
2095  struct __strictest_alignment<_Tp, _Types...>
2096  {
2097  static const size_t _S_alignment =
2098  alignof(_Tp) > __strictest_alignment<_Types...>::_S_alignment
2099  ? alignof(_Tp) : __strictest_alignment<_Types...>::_S_alignment;
2100  static const size_t _S_size =
2101  sizeof(_Tp) > __strictest_alignment<_Types...>::_S_size
2102  ? sizeof(_Tp) : __strictest_alignment<_Types...>::_S_size;
2103  };
2104 
2105  /**
2106  * @brief Provide aligned storage for types.
2107  *
2108  * [meta.trans.other]
2109  *
2110  * Provides aligned storage for any of the provided types of at
2111  * least size _Len.
2112  *
2113  * @see aligned_storage
2114  */
2115  template <size_t _Len, typename... _Types>
2116  struct aligned_union
2117  {
2118  private:
2119  static_assert(sizeof...(_Types) != 0, "At least one type is required");
2120 
2121  using __strictest = __strictest_alignment<_Types...>;
2122  static const size_t _S_len = _Len > __strictest::_S_size
2123  ? _Len : __strictest::_S_size;
2124  public:
2125  /// The value of the strictest alignment of _Types.
2126  static const size_t alignment_value = __strictest::_S_alignment;
2127  /// The storage.
2128  typedef typename aligned_storage<_S_len, alignment_value>::type type;
2129  };
2130 
2131  template <size_t _Len, typename... _Types>
2132  const size_t aligned_union<_Len, _Types...>::alignment_value;
2133 
2134  /// @cond undocumented
2135 
2136  // Decay trait for arrays and functions, used for perfect forwarding
2137  // in make_pair, make_tuple, etc.
2138  template<typename _Up,
2139  bool _IsArray = is_array<_Up>::value,
2140  bool _IsFunction = is_function<_Up>::value>
2141  struct __decay_selector;
2142 
2143  // NB: DR 705.
2144  template<typename _Up>
2145  struct __decay_selector<_Up, false, false>
2146  { typedef __remove_cv_t<_Up> __type; };
2147 
2148  template<typename _Up>
2149  struct __decay_selector<_Up, true, false>
2150  { typedef typename remove_extent<_Up>::type* __type; };
2151 
2152  template<typename _Up>
2153  struct __decay_selector<_Up, false, true>
2154  { typedef typename add_pointer<_Up>::type __type; };
2155  /// @endcond
2156 
2157  /// decay
2158  template<typename _Tp>
2159  class decay
2160  {
2161  typedef typename remove_reference<_Tp>::type __remove_type;
2162 
2163  public:
2164  typedef typename __decay_selector<__remove_type>::__type type;
2165  };
2166 
2167  /// @cond undocumented
2168 
2169  // Helper which adds a reference to a type when given a reference_wrapper
2170  template<typename _Tp>
2171  struct __strip_reference_wrapper
2172  {
2173  typedef _Tp __type;
2174  };
2175 
2176  template<typename _Tp>
2177  struct __strip_reference_wrapper<reference_wrapper<_Tp> >
2178  {
2179  typedef _Tp& __type;
2180  };
2181 
2182  // __decay_t (std::decay_t for C++11).
2183  template<typename _Tp>
2184  using __decay_t = typename decay<_Tp>::type;
2185 
2186  template<typename _Tp>
2187  using __decay_and_strip = __strip_reference_wrapper<__decay_t<_Tp>>;
2188  /// @endcond
2189 
2190  // Primary template.
2191  /// Define a member typedef `type` only if a boolean constant is true.
2192  template<bool, typename _Tp = void>
2193  struct enable_if
2194  { };
2195 
2196  // Partial specialization for true.
2197  template<typename _Tp>
2198  struct enable_if<true, _Tp>
2199  { typedef _Tp type; };
2200 
2201  /// @cond undocumented
2202 
2203  // __enable_if_t (std::enable_if_t for C++11)
2204  template<bool _Cond, typename _Tp = void>
2205  using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
2206 
2207  // Helper for SFINAE constraints
2208  template<typename... _Cond>
2209  using _Require = __enable_if_t<__and_<_Cond...>::value>;
2210 
2211  // __remove_cvref_t (std::remove_cvref_t for C++11).
2212  template<typename _Tp>
2213  using __remove_cvref_t
2214  = typename remove_cv<typename remove_reference<_Tp>::type>::type;
2215  /// @endcond
2216 
2217  // Primary template.
2218  /// Define a member typedef @c type to one of two argument types.
2219  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2220  struct conditional
2221  { typedef _Iftrue type; };
2222 
2223  // Partial specialization for false.
2224  template<typename _Iftrue, typename _Iffalse>
2225  struct conditional<false, _Iftrue, _Iffalse>
2226  { typedef _Iffalse type; };
2227 
2228  /// common_type
2229  template<typename... _Tp>
2230  struct common_type;
2231 
2232  // Sfinae-friendly common_type implementation:
2233 
2234  /// @cond undocumented
2235  struct __do_common_type_impl
2236  {
2237  template<typename _Tp, typename _Up>
2238  using __cond_t
2239  = decltype(true ? std::declval<_Tp>() : std::declval<_Up>());
2240 
2241  // if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2242  // denotes a valid type, let C denote that type.
2243  template<typename _Tp, typename _Up>
2244  static __success_type<__decay_t<__cond_t<_Tp, _Up>>>
2245  _S_test(int);
2246 
2247 #if __cplusplus > 201703L
2248  // Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type,
2249  // let C denote the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
2250  template<typename _Tp, typename _Up>
2251  static __success_type<__remove_cvref_t<__cond_t<const _Tp&, const _Up&>>>
2252  _S_test_2(int);
2253 #endif
2254 
2255  template<typename, typename>
2256  static __failure_type
2257  _S_test_2(...);
2258 
2259  template<typename _Tp, typename _Up>
2260  static decltype(_S_test_2<_Tp, _Up>(0))
2261  _S_test(...);
2262  };
2263 
2264  // If sizeof...(T) is zero, there shall be no member type.
2265  template<>
2266  struct common_type<>
2267  { };
2268 
2269  // If sizeof...(T) is one, the same type, if any, as common_type_t<T0, T0>.
2270  template<typename _Tp0>
2271  struct common_type<_Tp0>
2272  : public common_type<_Tp0, _Tp0>
2273  { };
2274 
2275  // If sizeof...(T) is two, ...
2276  template<typename _Tp1, typename _Tp2,
2277  typename _Dp1 = __decay_t<_Tp1>, typename _Dp2 = __decay_t<_Tp2>>
2278  struct __common_type_impl
2279  {
2280  // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false,
2281  // let C denote the same type, if any, as common_type_t<D1, D2>.
2282  using type = common_type<_Dp1, _Dp2>;
2283  };
2284 
2285  template<typename _Tp1, typename _Tp2>
2286  struct __common_type_impl<_Tp1, _Tp2, _Tp1, _Tp2>
2287  : private __do_common_type_impl
2288  {
2289  // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2290  // denotes a valid type, let C denote that type.
2291  using type = decltype(_S_test<_Tp1, _Tp2>(0));
2292  };
2293 
2294  // If sizeof...(T) is two, ...
2295  template<typename _Tp1, typename _Tp2>
2296  struct common_type<_Tp1, _Tp2>
2297  : public __common_type_impl<_Tp1, _Tp2>::type
2298  { };
2299 
2300  template<typename...>
2301  struct __common_type_pack
2302  { };
2303 
2304  template<typename, typename, typename = void>
2305  struct __common_type_fold;
2306 
2307  // If sizeof...(T) is greater than two, ...
2308  template<typename _Tp1, typename _Tp2, typename... _Rp>
2309  struct common_type<_Tp1, _Tp2, _Rp...>
2310  : public __common_type_fold<common_type<_Tp1, _Tp2>,
2311  __common_type_pack<_Rp...>>
2312  { };
2313 
2314  // Let C denote the same type, if any, as common_type_t<T1, T2>.
2315  // If there is such a type C, type shall denote the same type, if any,
2316  // as common_type_t<C, R...>.
2317  template<typename _CTp, typename... _Rp>
2318  struct __common_type_fold<_CTp, __common_type_pack<_Rp...>,
2319  __void_t<typename _CTp::type>>
2320  : public common_type<typename _CTp::type, _Rp...>
2321  { };
2322 
2323  // Otherwise, there shall be no member type.
2324  template<typename _CTp, typename _Rp>
2325  struct __common_type_fold<_CTp, _Rp, void>
2326  { };
2327 
2328  template<typename _Tp, bool = is_enum<_Tp>::value>
2329  struct __underlying_type_impl
2330  {
2331  using type = __underlying_type(_Tp);
2332  };
2333 
2334  template<typename _Tp>
2335  struct __underlying_type_impl<_Tp, false>
2336  { };
2337  /// @endcond
2338 
2339  /// The underlying type of an enum.
2340  template<typename _Tp>
2341  struct underlying_type
2342  : public __underlying_type_impl<_Tp>
2343  { };
2344 
2345  /// @cond undocumented
2346  template<typename _Tp>
2347  struct __declval_protector
2348  {
2349  static const bool __stop = false;
2350  };
2351  /// @endcond
2352 
2353  /** Utility to simplify expressions used in unevaluated operands
2354  * @since C++11
2355  * @ingroup utilities
2356  */
2357  template<typename _Tp>
2358  auto declval() noexcept -> decltype(__declval<_Tp>(0))
2359  {
2360  static_assert(__declval_protector<_Tp>::__stop,
2361  "declval() must not be used!");
2362  return __declval<_Tp>(0);
2363  }
2364 
2365  /// result_of
2366  template<typename _Signature>
2367  struct result_of;
2368 
2369  // Sfinae-friendly result_of implementation:
2370 
2371 #define __cpp_lib_result_of_sfinae 201210
2372 
2373  /// @cond undocumented
2374  struct __invoke_memfun_ref { };
2375  struct __invoke_memfun_deref { };
2376  struct __invoke_memobj_ref { };
2377  struct __invoke_memobj_deref { };
2378  struct __invoke_other { };
2379 
2380  // Associate a tag type with a specialization of __success_type.
2381  template<typename _Tp, typename _Tag>
2382  struct __result_of_success : __success_type<_Tp>
2383  { using __invoke_type = _Tag; };
2384 
2385  // [func.require] paragraph 1 bullet 1:
2386  struct __result_of_memfun_ref_impl
2387  {
2388  template<typename _Fp, typename _Tp1, typename... _Args>
2389  static __result_of_success<decltype(
2390  (std::declval<_Tp1>().*std::declval<_Fp>())(std::declval<_Args>()...)
2391  ), __invoke_memfun_ref> _S_test(int);
2392 
2393  template<typename...>
2394  static __failure_type _S_test(...);
2395  };
2396 
2397  template<typename _MemPtr, typename _Arg, typename... _Args>
2398  struct __result_of_memfun_ref
2399  : private __result_of_memfun_ref_impl
2400  {
2401  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2402  };
2403 
2404  // [func.require] paragraph 1 bullet 2:
2405  struct __result_of_memfun_deref_impl
2406  {
2407  template<typename _Fp, typename _Tp1, typename... _Args>
2408  static __result_of_success<decltype(
2409  ((*std::declval<_Tp1>()).*std::declval<_Fp>())(std::declval<_Args>()...)
2410  ), __invoke_memfun_deref> _S_test(int);
2411 
2412  template<typename...>
2413  static __failure_type _S_test(...);
2414  };
2415 
2416  template<typename _MemPtr, typename _Arg, typename... _Args>
2417  struct __result_of_memfun_deref
2418  : private __result_of_memfun_deref_impl
2419  {
2420  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2421  };
2422 
2423  // [func.require] paragraph 1 bullet 3:
2424  struct __result_of_memobj_ref_impl
2425  {
2426  template<typename _Fp, typename _Tp1>
2427  static __result_of_success<decltype(
2428  std::declval<_Tp1>().*std::declval<_Fp>()
2429  ), __invoke_memobj_ref> _S_test(int);
2430 
2431  template<typename, typename>
2432  static __failure_type _S_test(...);
2433  };
2434 
2435  template<typename _MemPtr, typename _Arg>
2436  struct __result_of_memobj_ref
2437  : private __result_of_memobj_ref_impl
2438  {
2439  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2440  };
2441 
2442  // [func.require] paragraph 1 bullet 4:
2443  struct __result_of_memobj_deref_impl
2444  {
2445  template<typename _Fp, typename _Tp1>
2446  static __result_of_success<decltype(
2447  (*std::declval<_Tp1>()).*std::declval<_Fp>()
2448  ), __invoke_memobj_deref> _S_test(int);
2449 
2450  template<typename, typename>
2451  static __failure_type _S_test(...);
2452  };
2453 
2454  template<typename _MemPtr, typename _Arg>
2455  struct __result_of_memobj_deref
2456  : private __result_of_memobj_deref_impl
2457  {
2458  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2459  };
2460 
2461  template<typename _MemPtr, typename _Arg>
2462  struct __result_of_memobj;
2463 
2464  template<typename _Res, typename _Class, typename _Arg>
2465  struct __result_of_memobj<_Res _Class::*, _Arg>
2466  {
2467  typedef __remove_cvref_t<_Arg> _Argval;
2468  typedef _Res _Class::* _MemPtr;
2469  typedef typename conditional<__or_<is_same<_Argval, _Class>,
2470  is_base_of<_Class, _Argval>>::value,
2471  __result_of_memobj_ref<_MemPtr, _Arg>,
2472  __result_of_memobj_deref<_MemPtr, _Arg>
2473  >::type::type type;
2474  };
2475 
2476  template<typename _MemPtr, typename _Arg, typename... _Args>
2477  struct __result_of_memfun;
2478 
2479  template<typename _Res, typename _Class, typename _Arg, typename... _Args>
2480  struct __result_of_memfun<_Res _Class::*, _Arg, _Args...>
2481  {
2482  typedef typename remove_reference<_Arg>::type _Argval;
2483  typedef _Res _Class::* _MemPtr;
2484  typedef typename conditional<is_base_of<_Class, _Argval>::value,
2485  __result_of_memfun_ref<_MemPtr, _Arg, _Args...>,
2486  __result_of_memfun_deref<_MemPtr, _Arg, _Args...>
2487  >::type::type type;
2488  };
2489 
2490  // _GLIBCXX_RESOLVE_LIB_DEFECTS
2491  // 2219. INVOKE-ing a pointer to member with a reference_wrapper
2492  // as the object expression
2493 
2494  // Used by result_of, invoke etc. to unwrap a reference_wrapper.
2495  template<typename _Tp, typename _Up = __remove_cvref_t<_Tp>>
2496  struct __inv_unwrap
2497  {
2498  using type = _Tp;
2499  };
2500 
2501  template<typename _Tp, typename _Up>
2502  struct __inv_unwrap<_Tp, reference_wrapper<_Up>>
2503  {
2504  using type = _Up&;
2505  };
2506 
2507  template<bool, bool, typename _Functor, typename... _ArgTypes>
2508  struct __result_of_impl
2509  {
2510  typedef __failure_type type;
2511  };
2512 
2513  template<typename _MemPtr, typename _Arg>
2514  struct __result_of_impl<true, false, _MemPtr, _Arg>
2515  : public __result_of_memobj<__decay_t<_MemPtr>,
2516  typename __inv_unwrap<_Arg>::type>
2517  { };
2518 
2519  template<typename _MemPtr, typename _Arg, typename... _Args>
2520  struct __result_of_impl<false, true, _MemPtr, _Arg, _Args...>
2521  : public __result_of_memfun<__decay_t<_MemPtr>,
2522  typename __inv_unwrap<_Arg>::type, _Args...>
2523  { };
2524 
2525  // [func.require] paragraph 1 bullet 5:
2526  struct __result_of_other_impl
2527  {
2528  template<typename _Fn, typename... _Args>
2529  static __result_of_success<decltype(
2530  std::declval<_Fn>()(std::declval<_Args>()...)
2531  ), __invoke_other> _S_test(int);
2532 
2533  template<typename...>
2534  static __failure_type _S_test(...);
2535  };
2536 
2537  template<typename _Functor, typename... _ArgTypes>
2538  struct __result_of_impl<false, false, _Functor, _ArgTypes...>
2539  : private __result_of_other_impl
2540  {
2541  typedef decltype(_S_test<_Functor, _ArgTypes...>(0)) type;
2542  };
2543 
2544  // __invoke_result (std::invoke_result for C++11)
2545  template<typename _Functor, typename... _ArgTypes>
2546  struct __invoke_result
2547  : public __result_of_impl<
2548  is_member_object_pointer<
2549  typename remove_reference<_Functor>::type
2550  >::value,
2551  is_member_function_pointer<
2552  typename remove_reference<_Functor>::type
2553  >::value,
2554  _Functor, _ArgTypes...
2555  >::type
2556  { };
2557  /// @endcond
2558 
2559  template<typename _Functor, typename... _ArgTypes>
2560  struct result_of<_Functor(_ArgTypes...)>
2561  : public __invoke_result<_Functor, _ArgTypes...>
2562  { };
2563 
2564 #if __cplusplus >= 201402L
2565  /// Alias template for aligned_storage
2566  template<size_t _Len, size_t _Align =
2567  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2568  using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
2569 
2570  template <size_t _Len, typename... _Types>
2571  using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
2572 
2573  /// Alias template for decay
2574  template<typename _Tp>
2575  using decay_t = typename decay<_Tp>::type;
2576 
2577  /// Alias template for enable_if
2578  template<bool _Cond, typename _Tp = void>
2579  using enable_if_t = typename enable_if<_Cond, _Tp>::type;
2580 
2581  /// Alias template for conditional
2582  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2583  using conditional_t = typename conditional<_Cond, _Iftrue, _Iffalse>::type;
2584 
2585  /// Alias template for common_type
2586  template<typename... _Tp>
2587  using common_type_t = typename common_type<_Tp...>::type;
2588 
2589  /// Alias template for underlying_type
2590  template<typename _Tp>
2591  using underlying_type_t = typename underlying_type<_Tp>::type;
2592 
2593  /// Alias template for result_of
2594  template<typename _Tp>
2595  using result_of_t = typename result_of<_Tp>::type;
2596 #endif // C++14
2597 
2598 #if __cplusplus >= 201703L || !defined(__STRICT_ANSI__) // c++17 or gnu++11
2599 #define __cpp_lib_void_t 201411
2600  /// A metafunction that always yields void, used for detecting valid types.
2601  template<typename...> using void_t = void;
2602 #endif
2603 
2604  /// @cond undocumented
2605 
2606  /// Implementation of the detection idiom (negative case).
2607  template<typename _Default, typename _AlwaysVoid,
2608  template<typename...> class _Op, typename... _Args>
2609  struct __detector
2610  {
2611  using value_t = false_type;
2612  using type = _Default;
2613  };
2614 
2615  /// Implementation of the detection idiom (positive case).
2616  template<typename _Default, template<typename...> class _Op,
2617  typename... _Args>
2618  struct __detector<_Default, __void_t<_Op<_Args...>>, _Op, _Args...>
2619  {
2620  using value_t = true_type;
2621  using type = _Op<_Args...>;
2622  };
2623 
2624  // Detect whether _Op<_Args...> is a valid type, use _Default if not.
2625  template<typename _Default, template<typename...> class _Op,
2626  typename... _Args>
2627  using __detected_or = __detector<_Default, void, _Op, _Args...>;
2628 
2629  // _Op<_Args...> if that is a valid type, otherwise _Default.
2630  template<typename _Default, template<typename...> class _Op,
2631  typename... _Args>
2632  using __detected_or_t
2633  = typename __detected_or<_Default, _Op, _Args...>::type;
2634 
2635  /**
2636  * Use SFINAE to determine if the type _Tp has a publicly-accessible
2637  * member type _NTYPE.
2638  */
2639 #define _GLIBCXX_HAS_NESTED_TYPE(_NTYPE) \
2640  template<typename _Tp, typename = __void_t<>> \
2641  struct __has_##_NTYPE \
2642  : false_type \
2643  { }; \
2644  template<typename _Tp> \
2645  struct __has_##_NTYPE<_Tp, __void_t<typename _Tp::_NTYPE>> \
2646  : true_type \
2647  { };
2648 
2649  template <typename _Tp>
2650  struct __is_swappable;
2651 
2652  template <typename _Tp>
2653  struct __is_nothrow_swappable;
2654 
2655  template<typename>
2656  struct __is_tuple_like_impl : false_type
2657  { };
2658 
2659  template<typename... _Tps>
2660  struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
2661  { };
2662 
2663  // Internal type trait that allows us to sfinae-protect tuple_cat.
2664  template<typename _Tp>
2665  struct __is_tuple_like
2666  : public __is_tuple_like_impl<__remove_cvref_t<_Tp>>::type
2667  { };
2668  /// @endcond
2669 
2670  template<typename _Tp>
2671  _GLIBCXX20_CONSTEXPR
2672  inline
2673  _Require<__not_<__is_tuple_like<_Tp>>,
2674  is_move_constructible<_Tp>,
2675  is_move_assignable<_Tp>>
2676  swap(_Tp&, _Tp&)
2677  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
2678  is_nothrow_move_assignable<_Tp>>::value);
2679 
2680  template<typename _Tp, size_t _Nm>
2681  _GLIBCXX20_CONSTEXPR
2682  inline
2683  __enable_if_t<__is_swappable<_Tp>::value>
2684  swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
2685  noexcept(__is_nothrow_swappable<_Tp>::value);
2686 
2687  /// @cond undocumented
2688  namespace __swappable_details {
2689  using std::swap;
2690 
2691  struct __do_is_swappable_impl
2692  {
2693  template<typename _Tp, typename
2694  = decltype(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))>
2695  static true_type __test(int);
2696 
2697  template<typename>
2698  static false_type __test(...);
2699  };
2700 
2701  struct __do_is_nothrow_swappable_impl
2702  {
2703  template<typename _Tp>
2704  static __bool_constant<
2705  noexcept(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))
2706  > __test(int);
2707 
2708  template<typename>
2709  static false_type __test(...);
2710  };
2711 
2712  } // namespace __swappable_details
2713 
2714  template<typename _Tp>
2715  struct __is_swappable_impl
2716  : public __swappable_details::__do_is_swappable_impl
2717  {
2718  typedef decltype(__test<_Tp>(0)) type;
2719  };
2720 
2721  template<typename _Tp>
2722  struct __is_nothrow_swappable_impl
2723  : public __swappable_details::__do_is_nothrow_swappable_impl
2724  {
2725  typedef decltype(__test<_Tp>(0)) type;
2726  };
2727 
2728  template<typename _Tp>
2729  struct __is_swappable
2730  : public __is_swappable_impl<_Tp>::type
2731  { };
2732 
2733  template<typename _Tp>
2734  struct __is_nothrow_swappable
2735  : public __is_nothrow_swappable_impl<_Tp>::type
2736  { };
2737  /// @endcond
2738 
2739 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2740 #define __cpp_lib_is_swappable 201603
2741  /// Metafunctions used for detecting swappable types: p0185r1
2742 
2743  /// is_swappable
2744  template<typename _Tp>
2745  struct is_swappable
2746  : public __is_swappable_impl<_Tp>::type
2747  {
2748  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2749  "template argument must be a complete class or an unbounded array");
2750  };
2751 
2752  /// is_nothrow_swappable
2753  template<typename _Tp>
2754  struct is_nothrow_swappable
2755  : public __is_nothrow_swappable_impl<_Tp>::type
2756  {
2757  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2758  "template argument must be a complete class or an unbounded array");
2759  };
2760 
2761 #if __cplusplus >= 201402L
2762  /// is_swappable_v
2763  template<typename _Tp>
2764  _GLIBCXX17_INLINE constexpr bool is_swappable_v =
2765  is_swappable<_Tp>::value;
2766 
2767  /// is_nothrow_swappable_v
2768  template<typename _Tp>
2769  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_v =
2770  is_nothrow_swappable<_Tp>::value;
2771 #endif // __cplusplus >= 201402L
2772 
2773  /// @cond undocumented
2774  namespace __swappable_with_details {
2775  using std::swap;
2776 
2777  struct __do_is_swappable_with_impl
2778  {
2779  template<typename _Tp, typename _Up, typename
2780  = decltype(swap(std::declval<_Tp>(), std::declval<_Up>())),
2781  typename
2782  = decltype(swap(std::declval<_Up>(), std::declval<_Tp>()))>
2783  static true_type __test(int);
2784 
2785  template<typename, typename>
2786  static false_type __test(...);
2787  };
2788 
2789  struct __do_is_nothrow_swappable_with_impl
2790  {
2791  template<typename _Tp, typename _Up>
2792  static __bool_constant<
2793  noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()))
2794  &&
2795  noexcept(swap(std::declval<_Up>(), std::declval<_Tp>()))
2796  > __test(int);
2797 
2798  template<typename, typename>
2799  static false_type __test(...);
2800  };
2801 
2802  } // namespace __swappable_with_details
2803 
2804  template<typename _Tp, typename _Up>
2805  struct __is_swappable_with_impl
2806  : public __swappable_with_details::__do_is_swappable_with_impl
2807  {
2808  typedef decltype(__test<_Tp, _Up>(0)) type;
2809  };
2810 
2811  // Optimization for the homogenous lvalue case, not required:
2812  template<typename _Tp>
2813  struct __is_swappable_with_impl<_Tp&, _Tp&>
2814  : public __swappable_details::__do_is_swappable_impl
2815  {
2816  typedef decltype(__test<_Tp&>(0)) type;
2817  };
2818 
2819  template<typename _Tp, typename _Up>
2820  struct __is_nothrow_swappable_with_impl
2821  : public __swappable_with_details::__do_is_nothrow_swappable_with_impl
2822  {
2823  typedef decltype(__test<_Tp, _Up>(0)) type;
2824  };
2825 
2826  // Optimization for the homogenous lvalue case, not required:
2827  template<typename _Tp>
2828  struct __is_nothrow_swappable_with_impl<_Tp&, _Tp&>
2829  : public __swappable_details::__do_is_nothrow_swappable_impl
2830  {
2831  typedef decltype(__test<_Tp&>(0)) type;
2832  };
2833  /// @endcond
2834 
2835  /// is_swappable_with
2836  template<typename _Tp, typename _Up>
2837  struct is_swappable_with
2838  : public __is_swappable_with_impl<_Tp, _Up>::type
2839  {
2840  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2841  "first template argument must be a complete class or an unbounded array");
2842  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2843  "second template argument must be a complete class or an unbounded array");
2844  };
2845 
2846  /// is_nothrow_swappable_with
2847  template<typename _Tp, typename _Up>
2848  struct is_nothrow_swappable_with
2849  : public __is_nothrow_swappable_with_impl<_Tp, _Up>::type
2850  {
2851  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2852  "first template argument must be a complete class or an unbounded array");
2853  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2854  "second template argument must be a complete class or an unbounded array");
2855  };
2856 
2857 #if __cplusplus >= 201402L
2858  /// is_swappable_with_v
2859  template<typename _Tp, typename _Up>
2860  _GLIBCXX17_INLINE constexpr bool is_swappable_with_v =
2861  is_swappable_with<_Tp, _Up>::value;
2862 
2863  /// is_nothrow_swappable_with_v
2864  template<typename _Tp, typename _Up>
2865  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_with_v =
2866  is_nothrow_swappable_with<_Tp, _Up>::value;
2867 #endif // __cplusplus >= 201402L
2868 
2869 #endif// c++1z or gnu++11
2870 
2871  /// @cond undocumented
2872 
2873  // __is_invocable (std::is_invocable for C++11)
2874 
2875  // The primary template is used for invalid INVOKE expressions.
2876  template<typename _Result, typename _Ret,
2877  bool = is_void<_Ret>::value, typename = void>
2878  struct __is_invocable_impl
2879  : false_type
2880  {
2881  using __nothrow_type = false_type; // For is_nothrow_invocable_r
2882  };
2883 
2884  // Used for valid INVOKE and INVOKE<void> expressions.
2885  template<typename _Result, typename _Ret>
2886  struct __is_invocable_impl<_Result, _Ret,
2887  /* is_void<_Ret> = */ true,
2888  __void_t<typename _Result::type>>
2889  : true_type
2890  {
2891  using __nothrow_type = true_type; // For is_nothrow_invocable_r
2892  };
2893 
2894 #pragma GCC diagnostic push
2895 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
2896  // Used for INVOKE<R> expressions to check the implicit conversion to R.
2897  template<typename _Result, typename _Ret>
2898  struct __is_invocable_impl<_Result, _Ret,
2899  /* is_void<_Ret> = */ false,
2900  __void_t<typename _Result::type>>
2901  {
2902  private:
2903  // The type of the INVOKE expression.
2904  // Unlike declval, this doesn't add_rvalue_reference, so it respects
2905  // guaranteed copy elision.
2906  static typename _Result::type _S_get() noexcept;
2907 
2908  template<typename _Tp>
2909  static void _S_conv(_Tp) noexcept;
2910 
2911  // This overload is viable if INVOKE(f, args...) can convert to _Tp.
2912  template<typename _Tp, bool _Check_Noex = false,
2913  typename = decltype(_S_conv<_Tp>(_S_get())),
2914  bool _Noex = noexcept(_S_conv<_Tp>(_S_get()))>
2915  static __bool_constant<_Check_Noex ? _Noex : true>
2916  _S_test(int);
2917 
2918  template<typename _Tp, bool = false>
2919  static false_type
2920  _S_test(...);
2921 
2922  public:
2923  // For is_invocable_r
2924  using type = decltype(_S_test<_Ret>(1));
2925 
2926  // For is_nothrow_invocable_r
2927  using __nothrow_type = decltype(_S_test<_Ret, true>(1));
2928  };
2929 #pragma GCC diagnostic pop
2930 
2931  template<typename _Fn, typename... _ArgTypes>
2932  struct __is_invocable
2933  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
2934  { };
2935 
2936  template<typename _Fn, typename _Tp, typename... _Args>
2937  constexpr bool __call_is_nt(__invoke_memfun_ref)
2938  {
2939  using _Up = typename __inv_unwrap<_Tp>::type;
2940  return noexcept((std::declval<_Up>().*std::declval<_Fn>())(
2941  std::declval<_Args>()...));
2942  }
2943 
2944  template<typename _Fn, typename _Tp, typename... _Args>
2945  constexpr bool __call_is_nt(__invoke_memfun_deref)
2946  {
2947  return noexcept(((*std::declval<_Tp>()).*std::declval<_Fn>())(
2948  std::declval<_Args>()...));
2949  }
2950 
2951  template<typename _Fn, typename _Tp>
2952  constexpr bool __call_is_nt(__invoke_memobj_ref)
2953  {
2954  using _Up = typename __inv_unwrap<_Tp>::type;
2955  return noexcept(std::declval<_Up>().*std::declval<_Fn>());
2956  }
2957 
2958  template<typename _Fn, typename _Tp>
2959  constexpr bool __call_is_nt(__invoke_memobj_deref)
2960  {
2961  return noexcept((*std::declval<_Tp>()).*std::declval<_Fn>());
2962  }
2963 
2964  template<typename _Fn, typename... _Args>
2965  constexpr bool __call_is_nt(__invoke_other)
2966  {
2967  return noexcept(std::declval<_Fn>()(std::declval<_Args>()...));
2968  }
2969 
2970  template<typename _Result, typename _Fn, typename... _Args>
2971  struct __call_is_nothrow
2972  : __bool_constant<
2973  std::__call_is_nt<_Fn, _Args...>(typename _Result::__invoke_type{})
2974  >
2975  { };
2976 
2977  template<typename _Fn, typename... _Args>
2978  using __call_is_nothrow_
2979  = __call_is_nothrow<__invoke_result<_Fn, _Args...>, _Fn, _Args...>;
2980 
2981  // __is_nothrow_invocable (std::is_nothrow_invocable for C++11)
2982  template<typename _Fn, typename... _Args>
2983  struct __is_nothrow_invocable
2984  : __and_<__is_invocable<_Fn, _Args...>,
2985  __call_is_nothrow_<_Fn, _Args...>>::type
2986  { };
2987 
2988 #pragma GCC diagnostic push
2989 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
2990  struct __nonesuchbase {};
2991  struct __nonesuch : private __nonesuchbase {
2992  ~__nonesuch() = delete;
2993  __nonesuch(__nonesuch const&) = delete;
2994  void operator=(__nonesuch const&) = delete;
2995  };
2996 #pragma GCC diagnostic pop
2997  /// @endcond
2998 
2999 #if __cplusplus >= 201703L
3000 # define __cpp_lib_is_invocable 201703
3001 
3002  /// std::invoke_result
3003  template<typename _Functor, typename... _ArgTypes>
3004  struct invoke_result
3005  : public __invoke_result<_Functor, _ArgTypes...>
3006  {
3007  static_assert(std::__is_complete_or_unbounded(__type_identity<_Functor>{}),
3008  "_Functor must be a complete class or an unbounded array");
3009  static_assert((std::__is_complete_or_unbounded(
3010  __type_identity<_ArgTypes>{}) && ...),
3011  "each argument type must be a complete class or an unbounded array");
3012  };
3013 
3014  /// std::invoke_result_t
3015  template<typename _Fn, typename... _Args>
3016  using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;
3017 
3018  /// std::is_invocable
3019  template<typename _Fn, typename... _ArgTypes>
3020  struct is_invocable
3021  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
3022  {
3023  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3024  "_Fn must be a complete class or an unbounded array");
3025  static_assert((std::__is_complete_or_unbounded(
3026  __type_identity<_ArgTypes>{}) && ...),
3027  "each argument type must be a complete class or an unbounded array");
3028  };
3029 
3030  /// std::is_invocable_r
3031  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3032  struct is_invocable_r
3033  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>::type
3034  {
3035  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3036  "_Fn must be a complete class or an unbounded array");
3037  static_assert((std::__is_complete_or_unbounded(
3038  __type_identity<_ArgTypes>{}) && ...),
3039  "each argument type must be a complete class or an unbounded array");
3040  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3041  "_Ret must be a complete class or an unbounded array");
3042  };
3043 
3044  /// std::is_nothrow_invocable
3045  template<typename _Fn, typename... _ArgTypes>
3046  struct is_nothrow_invocable
3047  : __and_<__is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>,
3048  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3049  {
3050  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3051  "_Fn must be a complete class or an unbounded array");
3052  static_assert((std::__is_complete_or_unbounded(
3053  __type_identity<_ArgTypes>{}) && ...),
3054  "each argument type must be a complete class or an unbounded array");
3055  };
3056 
3057  /// @cond undocumented
3058  template<typename _Result, typename _Ret>
3059  using __is_nt_invocable_impl
3060  = typename __is_invocable_impl<_Result, _Ret>::__nothrow_type;
3061  /// @endcond
3062 
3063  /// std::is_nothrow_invocable_r
3064  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3065  struct is_nothrow_invocable_r
3066  : __and_<__is_nt_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>,
3067  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3068  {
3069  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3070  "_Fn must be a complete class or an unbounded array");
3071  static_assert((std::__is_complete_or_unbounded(
3072  __type_identity<_ArgTypes>{}) && ...),
3073  "each argument type must be a complete class or an unbounded array");
3074  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3075  "_Ret must be a complete class or an unbounded array");
3076  };
3077 #endif // C++17
3078 
3079 #if __cplusplus >= 201703L
3080 # define __cpp_lib_type_trait_variable_templates 201510L
3081  /**
3082  * @defgroup variable_templates Variable templates for type traits.
3083  * @ingroup metaprogramming
3084  *
3085  * The variable `is_foo_v<T>` is a boolean constant with the same value
3086  * as the type trait `is_foo<T>::value`.
3087  *
3088  * @since C++17
3089  */
3090 
3091  /** @ingroup variable_templates
3092  * @{
3093  */
3094 template <typename _Tp>
3095  inline constexpr bool is_void_v = is_void<_Tp>::value;
3096 template <typename _Tp>
3097  inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
3098 template <typename _Tp>
3099  inline constexpr bool is_integral_v = is_integral<_Tp>::value;
3100 template <typename _Tp>
3101  inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
3102 template <typename _Tp>
3103  inline constexpr bool is_array_v = is_array<_Tp>::value;
3104 template <typename _Tp>
3105  inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
3106 template <typename _Tp>
3107  inline constexpr bool is_lvalue_reference_v =
3108  is_lvalue_reference<_Tp>::value;
3109 template <typename _Tp>
3110  inline constexpr bool is_rvalue_reference_v =
3111  is_rvalue_reference<_Tp>::value;
3112 template <typename _Tp>
3113  inline constexpr bool is_member_object_pointer_v =
3114  is_member_object_pointer<_Tp>::value;
3115 template <typename _Tp>
3116  inline constexpr bool is_member_function_pointer_v =
3117  is_member_function_pointer<_Tp>::value;
3118 template <typename _Tp>
3119  inline constexpr bool is_enum_v = is_enum<_Tp>::value;
3120 template <typename _Tp>
3121  inline constexpr bool is_union_v = is_union<_Tp>::value;
3122 template <typename _Tp>
3123  inline constexpr bool is_class_v = is_class<_Tp>::value;
3124 template <typename _Tp>
3125  inline constexpr bool is_function_v = is_function<_Tp>::value;
3126 template <typename _Tp>
3127  inline constexpr bool is_reference_v = is_reference<_Tp>::value;
3128 template <typename _Tp>
3129  inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
3130 template <typename _Tp>
3131  inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
3132 template <typename _Tp>
3133  inline constexpr bool is_object_v = is_object<_Tp>::value;
3134 template <typename _Tp>
3135  inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
3136 template <typename _Tp>
3137  inline constexpr bool is_compound_v = is_compound<_Tp>::value;
3138 template <typename _Tp>
3139  inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
3140 template <typename _Tp>
3141  inline constexpr bool is_const_v = is_const<_Tp>::value;
3142 template <typename _Tp>
3143  inline constexpr bool is_volatile_v = is_volatile<_Tp>::value;
3144 template <typename _Tp>
3145  inline constexpr bool is_trivial_v = is_trivial<_Tp>::value;
3146 template <typename _Tp>
3147  inline constexpr bool is_trivially_copyable_v =
3148  is_trivially_copyable<_Tp>::value;
3149 template <typename _Tp>
3150  inline constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
3151 #pragma GCC diagnostic push
3152 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
3153 template <typename _Tp>
3154  _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
3155  inline constexpr bool is_pod_v = is_pod<_Tp>::value;
3156 template <typename _Tp>
3157  _GLIBCXX17_DEPRECATED
3158  inline constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
3159 #pragma GCC diagnostic pop
3160  template <typename _Tp>
3161  inline constexpr bool is_empty_v = is_empty<_Tp>::value;
3162 template <typename _Tp>
3163  inline constexpr bool is_polymorphic_v = is_polymorphic<_Tp>::value;
3164 template <typename _Tp>
3165  inline constexpr bool is_abstract_v = is_abstract<_Tp>::value;
3166 template <typename _Tp>
3167  inline constexpr bool is_final_v = is_final<_Tp>::value;
3168 template <typename _Tp>
3169  inline constexpr bool is_signed_v = is_signed<_Tp>::value;
3170 template <typename _Tp>
3171  inline constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
3172 template <typename _Tp, typename... _Args>
3173  inline constexpr bool is_constructible_v =
3174  is_constructible<_Tp, _Args...>::value;
3175 template <typename _Tp>
3176  inline constexpr bool is_default_constructible_v =
3177  is_default_constructible<_Tp>::value;
3178 template <typename _Tp>
3179  inline constexpr bool is_copy_constructible_v =
3180  is_copy_constructible<_Tp>::value;
3181 template <typename _Tp>
3182  inline constexpr bool is_move_constructible_v =
3183  is_move_constructible<_Tp>::value;
3184 template <typename _Tp, typename _Up>
3185  inline constexpr bool is_assignable_v = is_assignable<_Tp, _Up>::value;
3186 template <typename _Tp>
3187  inline constexpr bool is_copy_assignable_v = is_copy_assignable<_Tp>::value;
3188 template <typename _Tp>
3189  inline constexpr bool is_move_assignable_v = is_move_assignable<_Tp>::value;
3190 template <typename _Tp>
3191  inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
3192 template <typename _Tp, typename... _Args>
3193  inline constexpr bool is_trivially_constructible_v =
3194  is_trivially_constructible<_Tp, _Args...>::value;
3195 template <typename _Tp>
3196  inline constexpr bool is_trivially_default_constructible_v =
3197  is_trivially_default_constructible<_Tp>::value;
3198 template <typename _Tp>
3199  inline constexpr bool is_trivially_copy_constructible_v =
3200  is_trivially_copy_constructible<_Tp>::value;
3201 template <typename _Tp>
3202  inline constexpr bool is_trivially_move_constructible_v =
3203  is_trivially_move_constructible<_Tp>::value;
3204 template <typename _Tp, typename _Up>
3205  inline constexpr bool is_trivially_assignable_v =
3206  is_trivially_assignable<_Tp, _Up>::value;
3207 template <typename _Tp>
3208  inline constexpr bool is_trivially_copy_assignable_v =
3209  is_trivially_copy_assignable<_Tp>::value;
3210 template <typename _Tp>
3211  inline constexpr bool is_trivially_move_assignable_v =
3212  is_trivially_move_assignable<_Tp>::value;
3213 template <typename _Tp>
3214  inline constexpr bool is_trivially_destructible_v =
3215  is_trivially_destructible<_Tp>::value;
3216 template <typename _Tp, typename... _Args>
3217  inline constexpr bool is_nothrow_constructible_v =
3218  is_nothrow_constructible<_Tp, _Args...>::value;
3219 template <typename _Tp>
3220  inline constexpr bool is_nothrow_default_constructible_v =
3221  is_nothrow_default_constructible<_Tp>::value;
3222 template <typename _Tp>
3223  inline constexpr bool is_nothrow_copy_constructible_v =
3224  is_nothrow_copy_constructible<_Tp>::value;
3225 template <typename _Tp>
3226  inline constexpr bool is_nothrow_move_constructible_v =
3227  is_nothrow_move_constructible<_Tp>::value;
3228 template <typename _Tp, typename _Up>
3229  inline constexpr bool is_nothrow_assignable_v =
3230  is_nothrow_assignable<_Tp, _Up>::value;
3231 template <typename _Tp>
3232  inline constexpr bool is_nothrow_copy_assignable_v =
3233  is_nothrow_copy_assignable<_Tp>::value;
3234 template <typename _Tp>
3235  inline constexpr bool is_nothrow_move_assignable_v =
3236  is_nothrow_move_assignable<_Tp>::value;
3237 template <typename _Tp>
3238  inline constexpr bool is_nothrow_destructible_v =
3239  is_nothrow_destructible<_Tp>::value;
3240 template <typename _Tp>
3241  inline constexpr bool has_virtual_destructor_v =
3242  has_virtual_destructor<_Tp>::value;
3243 template <typename _Tp>
3244  inline constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
3245 template <typename _Tp>
3246  inline constexpr size_t rank_v = rank<_Tp>::value;
3247 template <typename _Tp, unsigned _Idx = 0>
3248  inline constexpr size_t extent_v = extent<_Tp, _Idx>::value;
3249 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
3250 template <typename _Tp, typename _Up>
3251  inline constexpr bool is_same_v = __is_same(_Tp, _Up);
3252 #else
3253 template <typename _Tp, typename _Up>
3254  inline constexpr bool is_same_v = std::is_same<_Tp, _Up>::value;
3255 #endif
3256 template <typename _Base, typename _Derived>
3257  inline constexpr bool is_base_of_v = is_base_of<_Base, _Derived>::value;
3258 template <typename _From, typename _To>
3259  inline constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
3260 template<typename _Fn, typename... _Args>
3261  inline constexpr bool is_invocable_v = is_invocable<_Fn, _Args...>::value;
3262 template<typename _Fn, typename... _Args>
3263  inline constexpr bool is_nothrow_invocable_v
3264  = is_nothrow_invocable<_Fn, _Args...>::value;
3265 template<typename _Ret, typename _Fn, typename... _Args>
3266  inline constexpr bool is_invocable_r_v
3267  = is_invocable_r<_Ret, _Fn, _Args...>::value;
3268 template<typename _Ret, typename _Fn, typename... _Args>
3269  inline constexpr bool is_nothrow_invocable_r_v
3270  = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;
3271 /// @}
3272 
3273 #ifdef _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP
3274 # define __cpp_lib_has_unique_object_representations 201606
3275  /// has_unique_object_representations
3276  template<typename _Tp>
3277  struct has_unique_object_representations
3278  : bool_constant<__has_unique_object_representations(
3279  remove_cv_t<remove_all_extents_t<_Tp>>
3280  )>
3281  {
3282  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
3283  "template argument must be a complete class or an unbounded array");
3284  };
3285 
3286  /// @ingroup variable_templates
3287  template<typename _Tp>
3288  inline constexpr bool has_unique_object_representations_v
3289  = has_unique_object_representations<_Tp>::value;
3290 #endif
3291 
3292 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE
3293 # define __cpp_lib_is_aggregate 201703
3294  /// is_aggregate
3295  template<typename _Tp>
3296  struct is_aggregate
3297  : bool_constant<__is_aggregate(remove_cv_t<_Tp>)>
3298  { };
3299 
3300  /// @ingroup variable_templates
3301  template<typename _Tp>
3302  inline constexpr bool is_aggregate_v = is_aggregate<_Tp>::value;
3303 #endif
3304 #endif // C++17
3305 
3306 #if __cplusplus > 201703L
3307 #define __cpp_lib_remove_cvref 201711L
3308 
3309  /// Remove references and cv-qualifiers.
3310  template<typename _Tp>
3311  struct remove_cvref
3312  : remove_cv<_Tp>
3313  { };
3314 
3315  template<typename _Tp>
3316  struct remove_cvref<_Tp&>
3317  : remove_cv<_Tp>
3318  { };
3319 
3320  template<typename _Tp>
3321  struct remove_cvref<_Tp&&>
3322  : remove_cv<_Tp>
3323  { };
3324 
3325  template<typename _Tp>
3326  using remove_cvref_t = typename remove_cvref<_Tp>::type;
3327 
3328 #define __cpp_lib_type_identity 201806L
3329  /// Identity metafunction.
3330  template<typename _Tp>
3331  struct type_identity { using type = _Tp; };
3332 
3333  template<typename _Tp>
3334  using type_identity_t = typename type_identity<_Tp>::type;
3335 
3336 #define __cpp_lib_unwrap_ref 201811L
3337 
3338  /// Unwrap a reference_wrapper
3339  template<typename _Tp>
3340  struct unwrap_reference { using type = _Tp; };
3341 
3342  template<typename _Tp>
3343  struct unwrap_reference<reference_wrapper<_Tp>> { using type = _Tp&; };
3344 
3345  template<typename _Tp>
3346  using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
3347 
3348  /// Decay type and if it's a reference_wrapper, unwrap it
3349  template<typename _Tp>
3350  struct unwrap_ref_decay { using type = unwrap_reference_t<decay_t<_Tp>>; };
3351 
3352  template<typename _Tp>
3353  using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
3354 
3355 #define __cpp_lib_bounded_array_traits 201902L
3356 
3357  /// True for a type that is an array of known bound.
3358  template<typename _Tp>
3359  struct is_bounded_array
3360  : public __is_array_known_bounds<_Tp>
3361  { };
3362 
3363  /// True for a type that is an array of unknown bound.
3364  template<typename _Tp>
3365  struct is_unbounded_array
3366  : public __is_array_unknown_bounds<_Tp>
3367  { };
3368 
3369  /// @ingroup variable_templates
3370  template<typename _Tp>
3371  inline constexpr bool is_bounded_array_v
3372  = is_bounded_array<_Tp>::value;
3373 
3374  /// @ingroup variable_templates
3375  template<typename _Tp>
3376  inline constexpr bool is_unbounded_array_v
3377  = is_unbounded_array<_Tp>::value;
3378 
3379 #if __cplusplus > 202002L
3380 #define __cpp_lib_is_scoped_enum 202011L
3381 
3382  /// @since C++23
3383  //@{
3384 
3385  template<typename _Tp>
3386  struct is_scoped_enum
3387  : false_type
3388  { };
3389 
3390  template<typename _Tp>
3391  requires __is_enum(_Tp)
3392  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3393  struct is_scoped_enum<_Tp>
3394  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3395  { };
3396 
3397  // FIXME remove this partial specialization and use remove_cv_t<_Tp> above
3398  // when PR c++/99968 is fixed.
3399  template<typename _Tp>
3400  requires __is_enum(_Tp)
3401  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3402  struct is_scoped_enum<const _Tp>
3403  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3404  { };
3405 
3406  /**
3407  * @ingroup variable_templates
3408  */
3409  template<typename _Tp>
3410  inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
3411 #endif // C++23
3412 
3413 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
3414 
3415 #define __cpp_lib_is_constant_evaluated 201811L
3416 
3417  /// Returns true only when called during constant evaluation.
3418  constexpr inline bool
3419  is_constant_evaluated() noexcept
3420  { return __builtin_is_constant_evaluated(); }
3421  /// @}
3422 #endif
3423 
3424  /// @cond undocumented
3425  template<typename _From, typename _To>
3426  using __copy_cv = typename __match_cv_qualifiers<_From, _To>::__type;
3427 
3428  template<typename _Xp, typename _Yp>
3429  using __cond_res
3430  = decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()());
3431 
3432  template<typename _Ap, typename _Bp, typename = void>
3433  struct __common_ref_impl
3434  { };
3435 
3436  // [meta.trans.other], COMMON-REF(A, B)
3437  template<typename _Ap, typename _Bp>
3438  using __common_ref = typename __common_ref_impl<_Ap, _Bp>::type;
3439 
3440  // COND-RES(COPYCV(X, Y) &, COPYCV(Y, X) &)
3441  template<typename _Xp, typename _Yp>
3442  using __condres_cvref
3443  = __cond_res<__copy_cv<_Xp, _Yp>&, __copy_cv<_Yp, _Xp>&>;
3444 
3445  // If A and B are both lvalue reference types, ...
3446  template<typename _Xp, typename _Yp>
3447  struct __common_ref_impl<_Xp&, _Yp&, __void_t<__condres_cvref<_Xp, _Yp>>>
3448  : enable_if<is_reference_v<__condres_cvref<_Xp, _Yp>>,
3449  __condres_cvref<_Xp, _Yp>>
3450  { };
3451 
3452  // let C be remove_reference_t<COMMON-REF(X&, Y&)>&&
3453  template<typename _Xp, typename _Yp>
3454  using __common_ref_C = remove_reference_t<__common_ref<_Xp&, _Yp&>>&&;
3455 
3456  // If A and B are both rvalue reference types, ...
3457  template<typename _Xp, typename _Yp>
3458  struct __common_ref_impl<_Xp&&, _Yp&&,
3459  _Require<is_convertible<_Xp&&, __common_ref_C<_Xp, _Yp>>,
3460  is_convertible<_Yp&&, __common_ref_C<_Xp, _Yp>>>>
3461  { using type = __common_ref_C<_Xp, _Yp>; };
3462 
3463  // let D be COMMON-REF(const X&, Y&)
3464  template<typename _Xp, typename _Yp>
3465  using __common_ref_D = __common_ref<const _Xp&, _Yp&>;
3466 
3467  // If A is an rvalue reference and B is an lvalue reference, ...
3468  template<typename _Xp, typename _Yp>
3469  struct __common_ref_impl<_Xp&&, _Yp&,
3470  _Require<is_convertible<_Xp&&, __common_ref_D<_Xp, _Yp>>>>
3471  { using type = __common_ref_D<_Xp, _Yp>; };
3472 
3473  // If A is an lvalue reference and B is an rvalue reference, ...
3474  template<typename _Xp, typename _Yp>
3475  struct __common_ref_impl<_Xp&, _Yp&&>
3476  : __common_ref_impl<_Yp&&, _Xp&>
3477  { };
3478  /// @endcond
3479 
3480  template<typename _Tp, typename _Up,
3481  template<typename> class _TQual, template<typename> class _UQual>
3482  struct basic_common_reference
3483  { };
3484 
3485  /// @cond undocumented
3486  template<typename _Tp>
3487  struct __xref
3488  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>; };
3489 
3490  template<typename _Tp>
3491  struct __xref<_Tp&>
3492  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&; };
3493 
3494  template<typename _Tp>
3495  struct __xref<_Tp&&>
3496  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&&; };
3497 
3498  template<typename _Tp1, typename _Tp2>
3499  using __basic_common_ref
3500  = typename basic_common_reference<remove_cvref_t<_Tp1>,
3501  remove_cvref_t<_Tp2>,
3502  __xref<_Tp1>::template __type,
3503  __xref<_Tp2>::template __type>::type;
3504  /// @endcond
3505 
3506  template<typename... _Tp>
3507  struct common_reference;
3508 
3509  template<typename... _Tp>
3510  using common_reference_t = typename common_reference<_Tp...>::type;
3511 
3512  // If sizeof...(T) is zero, there shall be no member type.
3513  template<>
3514  struct common_reference<>
3515  { };
3516 
3517  // If sizeof...(T) is one ...
3518  template<typename _Tp0>
3519  struct common_reference<_Tp0>
3520  { using type = _Tp0; };
3521 
3522  /// @cond undocumented
3523  template<typename _Tp1, typename _Tp2, int _Bullet = 1, typename = void>
3524  struct __common_reference_impl
3525  : __common_reference_impl<_Tp1, _Tp2, _Bullet + 1>
3526  { };
3527 
3528  // If sizeof...(T) is two ...
3529  template<typename _Tp1, typename _Tp2>
3530  struct common_reference<_Tp1, _Tp2>
3531  : __common_reference_impl<_Tp1, _Tp2>
3532  { };
3533 
3534  // If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, ...
3535  template<typename _Tp1, typename _Tp2>
3536  struct __common_reference_impl<_Tp1&, _Tp2&, 1,
3537  void_t<__common_ref<_Tp1&, _Tp2&>>>
3538  { using type = __common_ref<_Tp1&, _Tp2&>; };
3539 
3540  template<typename _Tp1, typename _Tp2>
3541  struct __common_reference_impl<_Tp1&&, _Tp2&&, 1,
3542  void_t<__common_ref<_Tp1&&, _Tp2&&>>>
3543  { using type = __common_ref<_Tp1&&, _Tp2&&>; };
3544 
3545  template<typename _Tp1, typename _Tp2>
3546  struct __common_reference_impl<_Tp1&, _Tp2&&, 1,
3547  void_t<__common_ref<_Tp1&, _Tp2&&>>>
3548  { using type = __common_ref<_Tp1&, _Tp2&&>; };
3549 
3550  template<typename _Tp1, typename _Tp2>
3551  struct __common_reference_impl<_Tp1&&, _Tp2&, 1,
3552  void_t<__common_ref<_Tp1&&, _Tp2&>>>
3553  { using type = __common_ref<_Tp1&&, _Tp2&>; };
3554 
3555  // Otherwise, if basic_common_reference<...>::type is well-formed, ...
3556  template<typename _Tp1, typename _Tp2>
3557  struct __common_reference_impl<_Tp1, _Tp2, 2,
3558  void_t<__basic_common_ref<_Tp1, _Tp2>>>
3559  { using type = __basic_common_ref<_Tp1, _Tp2>; };
3560 
3561  // Otherwise, if COND-RES(T1, T2) is well-formed, ...
3562  template<typename _Tp1, typename _Tp2>
3563  struct __common_reference_impl<_Tp1, _Tp2, 3,
3564  void_t<__cond_res<_Tp1, _Tp2>>>
3565  { using type = __cond_res<_Tp1, _Tp2>; };
3566 
3567  // Otherwise, if common_type_t<T1, T2> is well-formed, ...
3568  template<typename _Tp1, typename _Tp2>
3569  struct __common_reference_impl<_Tp1, _Tp2, 4,
3570  void_t<common_type_t<_Tp1, _Tp2>>>
3571  { using type = common_type_t<_Tp1, _Tp2>; };
3572 
3573  // Otherwise, there shall be no member type.
3574  template<typename _Tp1, typename _Tp2>
3575  struct __common_reference_impl<_Tp1, _Tp2, 5, void>
3576  { };
3577 
3578  // Otherwise, if sizeof...(T) is greater than two, ...
3579  template<typename _Tp1, typename _Tp2, typename... _Rest>
3580  struct common_reference<_Tp1, _Tp2, _Rest...>
3581  : __common_type_fold<common_reference<_Tp1, _Tp2>,
3582  __common_type_pack<_Rest...>>
3583  { };
3584 
3585  // Reuse __common_type_fold for common_reference<T1, T2, Rest...>
3586  template<typename _Tp1, typename _Tp2, typename... _Rest>
3587  struct __common_type_fold<common_reference<_Tp1, _Tp2>,
3588  __common_type_pack<_Rest...>,
3589  void_t<common_reference_t<_Tp1, _Tp2>>>
3590  : public common_reference<common_reference_t<_Tp1, _Tp2>, _Rest...>
3591  { };
3592  /// @endcond
3593 
3594 #endif // C++2a
3595 
3596  /// @} group metaprogramming
3597 
3598 _GLIBCXX_END_NAMESPACE_VERSION
3599 } // namespace std
3600 
3601 #endif // C++11
3602 
3603 #endif // _GLIBCXX_TYPE_TRAITS