libstdc++
type_traits
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1 // C++11 <type_traits> -*- C++ -*-
2 
3 // Copyright (C) 2007-2022 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 _Tp>
45  class reference_wrapper;
46 
47  /**
48  * @defgroup metaprogramming Metaprogramming
49  * @ingroup utilities
50  *
51  * Template utilities for compile-time introspection and modification,
52  * including type classification traits, type property inspection traits
53  * and type transformation traits.
54  *
55  * @since C++11
56  *
57  * @{
58  */
59 
60  /// integral_constant
61  template<typename _Tp, _Tp __v>
62  struct integral_constant
63  {
64  static constexpr _Tp value = __v;
65  typedef _Tp value_type;
66  typedef integral_constant<_Tp, __v> type;
67  constexpr operator value_type() const noexcept { return value; }
68 #if __cplusplus > 201103L
69 
70 #define __cpp_lib_integral_constant_callable 201304L
71 
72  constexpr value_type operator()() const noexcept { return value; }
73 #endif
74  };
75 
76 #if ! __cpp_inline_variables
77  template<typename _Tp, _Tp __v>
78  constexpr _Tp integral_constant<_Tp, __v>::value;
79 #endif
80 
81  /// The type used as a compile-time boolean with true value.
82  using true_type = integral_constant<bool, true>;
83 
84  /// The type used as a compile-time boolean with false value.
85  using false_type = integral_constant<bool, false>;
86 
87  /// @cond undocumented
88  /// bool_constant for C++11
89  template<bool __v>
90  using __bool_constant = integral_constant<bool, __v>;
91  /// @endcond
92 
93 #if __cplusplus >= 201703L
94 # define __cpp_lib_bool_constant 201505L
95  /// Alias template for compile-time boolean constant types.
96  /// @since C++17
97  template<bool __v>
98  using bool_constant = integral_constant<bool, __v>;
99 #endif
100 
101  // Metaprogramming helper types.
102 
103  template<bool>
104  struct __conditional
105  {
106  template<typename _Tp, typename>
107  using type = _Tp;
108  };
109 
110  template<>
111  struct __conditional<false>
112  {
113  template<typename, typename _Up>
114  using type = _Up;
115  };
116 
117  // More efficient version of std::conditional_t for internal use (and C++11)
118  template<bool _Cond, typename _If, typename _Else>
119  using __conditional_t
120  = typename __conditional<_Cond>::template type<_If, _Else>;
121 
122  /// @cond undocumented
123  template <typename _Type>
124  struct __type_identity
125  { using type = _Type; };
126 
127  template<typename _Tp>
128  using __type_identity_t = typename __type_identity<_Tp>::type;
129 
130  template<typename...>
131  struct __or_;
132 
133  template<>
134  struct __or_<>
135  : public false_type
136  { };
137 
138  template<typename _B1>
139  struct __or_<_B1>
140  : public _B1
141  { };
142 
143  template<typename _B1, typename _B2>
144  struct __or_<_B1, _B2>
145  : public __conditional_t<_B1::value, _B1, _B2>
146  { };
147 
148  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
149  struct __or_<_B1, _B2, _B3, _Bn...>
150  : public __conditional_t<_B1::value, _B1, __or_<_B2, _B3, _Bn...>>
151  { };
152 
153  template<typename...>
154  struct __and_;
155 
156  template<>
157  struct __and_<>
158  : public true_type
159  { };
160 
161  template<typename _B1>
162  struct __and_<_B1>
163  : public _B1
164  { };
165 
166  template<typename _B1, typename _B2>
167  struct __and_<_B1, _B2>
168  : public __conditional_t<_B1::value, _B2, _B1>
169  { };
170 
171  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
172  struct __and_<_B1, _B2, _B3, _Bn...>
173  : public __conditional_t<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>
174  { };
175 
176  template<typename _Pp>
177  struct __not_
178  : public __bool_constant<!bool(_Pp::value)>
179  { };
180  /// @endcond
181 
182 #if __cplusplus >= 201703L
183 
184  /// @cond undocumented
185  template<typename... _Bn>
186  inline constexpr bool __or_v = __or_<_Bn...>::value;
187  template<typename... _Bn>
188  inline constexpr bool __and_v = __and_<_Bn...>::value;
189  /// @endcond
190 
191 #define __cpp_lib_logical_traits 201510L
192 
193  template<typename... _Bn>
194  struct conjunction
195  : __and_<_Bn...>
196  { };
197 
198  template<typename... _Bn>
199  struct disjunction
200  : __or_<_Bn...>
201  { };
202 
203  template<typename _Pp>
204  struct negation
205  : __not_<_Pp>
206  { };
207 
208  /** @ingroup variable_templates
209  * @{
210  */
211  template<typename... _Bn>
212  inline constexpr bool conjunction_v = conjunction<_Bn...>::value;
213 
214  template<typename... _Bn>
215  inline constexpr bool disjunction_v = disjunction<_Bn...>::value;
216 
217  template<typename _Pp>
218  inline constexpr bool negation_v = negation<_Pp>::value;
219  /// @}
220 
221 #endif // C++17
222 
223  // Forward declarations
224  template<typename>
225  struct is_reference;
226  template<typename>
227  struct is_function;
228  template<typename>
229  struct is_void;
230  template<typename>
231  struct remove_cv;
232  template<typename>
233  struct is_const;
234 
235  /// @cond undocumented
236  template<typename>
237  struct __is_array_unknown_bounds;
238 
239  // Helper functions that return false_type for incomplete classes,
240  // incomplete unions and arrays of known bound from those.
241 
242  template <typename _Tp, size_t = sizeof(_Tp)>
243  constexpr true_type __is_complete_or_unbounded(__type_identity<_Tp>)
244  { return {}; }
245 
246  template <typename _TypeIdentity,
247  typename _NestedType = typename _TypeIdentity::type>
248  constexpr typename __or_<
249  is_reference<_NestedType>,
250  is_function<_NestedType>,
251  is_void<_NestedType>,
252  __is_array_unknown_bounds<_NestedType>
253  >::type __is_complete_or_unbounded(_TypeIdentity)
254  { return {}; }
255 
256  // For several sfinae-friendly trait implementations we transport both the
257  // result information (as the member type) and the failure information (no
258  // member type). This is very similar to std::enable_if, but we cannot use
259  // them, because we need to derive from them as an implementation detail.
260 
261  template<typename _Tp>
262  struct __success_type
263  { typedef _Tp type; };
264 
265  struct __failure_type
266  { };
267 
268  // __remove_cv_t (std::remove_cv_t for C++11).
269  template<typename _Tp>
270  using __remove_cv_t = typename remove_cv<_Tp>::type;
271 
272  // Primary type categories.
273 
274  template<typename>
275  struct __is_void_helper
276  : public false_type { };
277 
278  template<>
279  struct __is_void_helper<void>
280  : public true_type { };
281  /// @endcond
282 
283  /// is_void
284  template<typename _Tp>
285  struct is_void
286  : public __is_void_helper<__remove_cv_t<_Tp>>::type
287  { };
288 
289  /// @cond undocumented
290  template<typename>
291  struct __is_integral_helper
292  : public false_type { };
293 
294  template<>
295  struct __is_integral_helper<bool>
296  : public true_type { };
297 
298  template<>
299  struct __is_integral_helper<char>
300  : public true_type { };
301 
302  template<>
303  struct __is_integral_helper<signed char>
304  : public true_type { };
305 
306  template<>
307  struct __is_integral_helper<unsigned char>
308  : public true_type { };
309 
310  // We want is_integral<wchar_t> to be true (and make_signed/unsigned to work)
311  // even when libc doesn't provide working <wchar.h> and related functions,
312  // so don't check _GLIBCXX_USE_WCHAR_T here.
313  template<>
314  struct __is_integral_helper<wchar_t>
315  : public true_type { };
316 
317 #ifdef _GLIBCXX_USE_CHAR8_T
318  template<>
319  struct __is_integral_helper<char8_t>
320  : public true_type { };
321 #endif
322 
323  template<>
324  struct __is_integral_helper<char16_t>
325  : public true_type { };
326 
327  template<>
328  struct __is_integral_helper<char32_t>
329  : public true_type { };
330 
331  template<>
332  struct __is_integral_helper<short>
333  : public true_type { };
334 
335  template<>
336  struct __is_integral_helper<unsigned short>
337  : public true_type { };
338 
339  template<>
340  struct __is_integral_helper<int>
341  : public true_type { };
342 
343  template<>
344  struct __is_integral_helper<unsigned int>
345  : public true_type { };
346 
347  template<>
348  struct __is_integral_helper<long>
349  : public true_type { };
350 
351  template<>
352  struct __is_integral_helper<unsigned long>
353  : public true_type { };
354 
355  template<>
356  struct __is_integral_helper<long long>
357  : public true_type { };
358 
359  template<>
360  struct __is_integral_helper<unsigned long long>
361  : public true_type { };
362 
363  // Conditionalizing on __STRICT_ANSI__ here will break any port that
364  // uses one of these types for size_t.
365 #if defined(__GLIBCXX_TYPE_INT_N_0)
366  __extension__
367  template<>
368  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_0>
369  : public true_type { };
370 
371  __extension__
372  template<>
373  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_0>
374  : public true_type { };
375 #endif
376 #if defined(__GLIBCXX_TYPE_INT_N_1)
377  __extension__
378  template<>
379  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_1>
380  : public true_type { };
381 
382  __extension__
383  template<>
384  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_1>
385  : public true_type { };
386 #endif
387 #if defined(__GLIBCXX_TYPE_INT_N_2)
388  __extension__
389  template<>
390  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_2>
391  : public true_type { };
392 
393  __extension__
394  template<>
395  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_2>
396  : public true_type { };
397 #endif
398 #if defined(__GLIBCXX_TYPE_INT_N_3)
399  __extension__
400  template<>
401  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_3>
402  : public true_type { };
403 
404  __extension__
405  template<>
406  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_3>
407  : public true_type { };
408 #endif
409  /// @endcond
410 
411  /// is_integral
412  template<typename _Tp>
413  struct is_integral
414  : public __is_integral_helper<__remove_cv_t<_Tp>>::type
415  { };
416 
417  /// @cond undocumented
418  template<typename>
419  struct __is_floating_point_helper
420  : public false_type { };
421 
422  template<>
423  struct __is_floating_point_helper<float>
424  : public true_type { };
425 
426  template<>
427  struct __is_floating_point_helper<double>
428  : public true_type { };
429 
430  template<>
431  struct __is_floating_point_helper<long double>
432  : public true_type { };
433 
434 #if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
435  template<>
436  struct __is_floating_point_helper<__float128>
437  : public true_type { };
438 #endif
439  /// @endcond
440 
441  /// is_floating_point
442  template<typename _Tp>
443  struct is_floating_point
444  : public __is_floating_point_helper<__remove_cv_t<_Tp>>::type
445  { };
446 
447  /// is_array
448  template<typename>
449  struct is_array
450  : public false_type { };
451 
452  template<typename _Tp, std::size_t _Size>
453  struct is_array<_Tp[_Size]>
454  : public true_type { };
455 
456  template<typename _Tp>
457  struct is_array<_Tp[]>
458  : public true_type { };
459 
460  template<typename>
461  struct __is_pointer_helper
462  : public false_type { };
463 
464  template<typename _Tp>
465  struct __is_pointer_helper<_Tp*>
466  : public true_type { };
467 
468  /// is_pointer
469  template<typename _Tp>
470  struct is_pointer
471  : public __is_pointer_helper<__remove_cv_t<_Tp>>::type
472  { };
473 
474  /// is_lvalue_reference
475  template<typename>
476  struct is_lvalue_reference
477  : public false_type { };
478 
479  template<typename _Tp>
480  struct is_lvalue_reference<_Tp&>
481  : public true_type { };
482 
483  /// is_rvalue_reference
484  template<typename>
485  struct is_rvalue_reference
486  : public false_type { };
487 
488  template<typename _Tp>
489  struct is_rvalue_reference<_Tp&&>
490  : public true_type { };
491 
492  template<typename>
493  struct __is_member_object_pointer_helper
494  : public false_type { };
495 
496  template<typename _Tp, typename _Cp>
497  struct __is_member_object_pointer_helper<_Tp _Cp::*>
498  : public __not_<is_function<_Tp>>::type { };
499 
500  /// is_member_object_pointer
501  template<typename _Tp>
502  struct is_member_object_pointer
503  : public __is_member_object_pointer_helper<__remove_cv_t<_Tp>>::type
504  { };
505 
506  template<typename>
507  struct __is_member_function_pointer_helper
508  : public false_type { };
509 
510  template<typename _Tp, typename _Cp>
511  struct __is_member_function_pointer_helper<_Tp _Cp::*>
512  : public is_function<_Tp>::type { };
513 
514  /// is_member_function_pointer
515  template<typename _Tp>
516  struct is_member_function_pointer
517  : public __is_member_function_pointer_helper<__remove_cv_t<_Tp>>::type
518  { };
519 
520  /// is_enum
521  template<typename _Tp>
522  struct is_enum
523  : public integral_constant<bool, __is_enum(_Tp)>
524  { };
525 
526  /// is_union
527  template<typename _Tp>
528  struct is_union
529  : public integral_constant<bool, __is_union(_Tp)>
530  { };
531 
532  /// is_class
533  template<typename _Tp>
534  struct is_class
535  : public integral_constant<bool, __is_class(_Tp)>
536  { };
537 
538  /// is_function
539  template<typename _Tp>
540  struct is_function
541  : public __bool_constant<!is_const<const _Tp>::value> { };
542 
543  template<typename _Tp>
544  struct is_function<_Tp&>
545  : public false_type { };
546 
547  template<typename _Tp>
548  struct is_function<_Tp&&>
549  : public false_type { };
550 
551 #define __cpp_lib_is_null_pointer 201309L
552 
553  template<typename>
554  struct __is_null_pointer_helper
555  : public false_type { };
556 
557  template<>
558  struct __is_null_pointer_helper<std::nullptr_t>
559  : public true_type { };
560 
561  /// is_null_pointer (LWG 2247).
562  template<typename _Tp>
563  struct is_null_pointer
564  : public __is_null_pointer_helper<__remove_cv_t<_Tp>>::type
565  { };
566 
567  /// __is_nullptr_t (deprecated extension).
568  /// @deprecated Non-standard. Use `is_null_pointer` instead.
569  template<typename _Tp>
570  struct __is_nullptr_t
571  : public is_null_pointer<_Tp>
572  { } _GLIBCXX_DEPRECATED_SUGGEST("std::is_null_pointer");
573 
574  // Composite type categories.
575 
576  /// is_reference
577  template<typename _Tp>
578  struct is_reference
579  : public __or_<is_lvalue_reference<_Tp>,
580  is_rvalue_reference<_Tp>>::type
581  { };
582 
583  /// is_arithmetic
584  template<typename _Tp>
585  struct is_arithmetic
586  : public __or_<is_integral<_Tp>, is_floating_point<_Tp>>::type
587  { };
588 
589  /// is_fundamental
590  template<typename _Tp>
591  struct is_fundamental
592  : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
593  is_null_pointer<_Tp>>::type
594  { };
595 
596  /// is_object
597  template<typename _Tp>
598  struct is_object
599  : public __not_<__or_<is_function<_Tp>, is_reference<_Tp>,
600  is_void<_Tp>>>::type
601  { };
602 
603  template<typename>
604  struct is_member_pointer;
605 
606  /// is_scalar
607  template<typename _Tp>
608  struct is_scalar
609  : public __or_<is_arithmetic<_Tp>, is_enum<_Tp>, is_pointer<_Tp>,
610  is_member_pointer<_Tp>, is_null_pointer<_Tp>>::type
611  { };
612 
613  /// is_compound
614  template<typename _Tp>
615  struct is_compound
616  : public __not_<is_fundamental<_Tp>>::type { };
617 
618  /// @cond undocumented
619  template<typename _Tp>
620  struct __is_member_pointer_helper
621  : public false_type { };
622 
623  template<typename _Tp, typename _Cp>
624  struct __is_member_pointer_helper<_Tp _Cp::*>
625  : public true_type { };
626  /// @endcond
627 
628  /// is_member_pointer
629  template<typename _Tp>
630  struct is_member_pointer
631  : public __is_member_pointer_helper<__remove_cv_t<_Tp>>::type
632  { };
633 
634  template<typename, typename>
635  struct is_same;
636 
637  /// @cond undocumented
638  template<typename _Tp, typename... _Types>
639  using __is_one_of = __or_<is_same<_Tp, _Types>...>;
640 
641  // Check if a type is one of the signed integer types.
642  __extension__
643  template<typename _Tp>
644  using __is_signed_integer = __is_one_of<__remove_cv_t<_Tp>,
645  signed char, signed short, signed int, signed long,
646  signed long long
647 #if defined(__GLIBCXX_TYPE_INT_N_0)
648  , signed __GLIBCXX_TYPE_INT_N_0
649 #endif
650 #if defined(__GLIBCXX_TYPE_INT_N_1)
651  , signed __GLIBCXX_TYPE_INT_N_1
652 #endif
653 #if defined(__GLIBCXX_TYPE_INT_N_2)
654  , signed __GLIBCXX_TYPE_INT_N_2
655 #endif
656 #if defined(__GLIBCXX_TYPE_INT_N_3)
657  , signed __GLIBCXX_TYPE_INT_N_3
658 #endif
659  >;
660 
661  // Check if a type is one of the unsigned integer types.
662  __extension__
663  template<typename _Tp>
664  using __is_unsigned_integer = __is_one_of<__remove_cv_t<_Tp>,
665  unsigned char, unsigned short, unsigned int, unsigned long,
666  unsigned long long
667 #if defined(__GLIBCXX_TYPE_INT_N_0)
668  , unsigned __GLIBCXX_TYPE_INT_N_0
669 #endif
670 #if defined(__GLIBCXX_TYPE_INT_N_1)
671  , unsigned __GLIBCXX_TYPE_INT_N_1
672 #endif
673 #if defined(__GLIBCXX_TYPE_INT_N_2)
674  , unsigned __GLIBCXX_TYPE_INT_N_2
675 #endif
676 #if defined(__GLIBCXX_TYPE_INT_N_3)
677  , unsigned __GLIBCXX_TYPE_INT_N_3
678 #endif
679  >;
680 
681  // Check if a type is one of the signed or unsigned integer types.
682  template<typename _Tp>
683  using __is_standard_integer
684  = __or_<__is_signed_integer<_Tp>, __is_unsigned_integer<_Tp>>;
685 
686  // __void_t (std::void_t for C++11)
687  template<typename...> using __void_t = void;
688 
689  // Utility to detect referenceable types ([defns.referenceable]).
690 
691  template<typename _Tp, typename = void>
692  struct __is_referenceable
693  : public false_type
694  { };
695 
696  template<typename _Tp>
697  struct __is_referenceable<_Tp, __void_t<_Tp&>>
698  : public true_type
699  { };
700  /// @endcond
701 
702  // Type properties.
703 
704  /// is_const
705  template<typename>
706  struct is_const
707  : public false_type { };
708 
709  template<typename _Tp>
710  struct is_const<_Tp const>
711  : public true_type { };
712 
713  /// is_volatile
714  template<typename>
715  struct is_volatile
716  : public false_type { };
717 
718  template<typename _Tp>
719  struct is_volatile<_Tp volatile>
720  : public true_type { };
721 
722  /// is_trivial
723  template<typename _Tp>
724  struct is_trivial
725  : public integral_constant<bool, __is_trivial(_Tp)>
726  {
727  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
728  "template argument must be a complete class or an unbounded array");
729  };
730 
731  /// is_trivially_copyable
732  template<typename _Tp>
733  struct is_trivially_copyable
734  : public integral_constant<bool, __is_trivially_copyable(_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_standard_layout
741  template<typename _Tp>
742  struct is_standard_layout
743  : public integral_constant<bool, __is_standard_layout(_Tp)>
744  {
745  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
746  "template argument must be a complete class or an unbounded array");
747  };
748 
749  /** is_pod
750  * @deprecated Deprecated in C++20.
751  * Use `is_standard_layout && is_trivial` instead.
752  */
753  // Could use is_standard_layout && is_trivial instead of the builtin.
754  template<typename _Tp>
755  struct
756  _GLIBCXX20_DEPRECATED("use is_standard_layout && is_trivial instead")
757  is_pod
758  : public integral_constant<bool, __is_pod(_Tp)>
759  {
760  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
761  "template argument must be a complete class or an unbounded array");
762  };
763 
764  /** is_literal_type
765  * @deprecated Deprecated in C++17, removed in C++20.
766  * The idea of a literal type isn't useful.
767  */
768  template<typename _Tp>
769  struct
770  _GLIBCXX17_DEPRECATED
771  is_literal_type
772  : public integral_constant<bool, __is_literal_type(_Tp)>
773  {
774  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
775  "template argument must be a complete class or an unbounded array");
776  };
777 
778  /// is_empty
779  template<typename _Tp>
780  struct is_empty
781  : public integral_constant<bool, __is_empty(_Tp)>
782  { };
783 
784  /// is_polymorphic
785  template<typename _Tp>
786  struct is_polymorphic
787  : public integral_constant<bool, __is_polymorphic(_Tp)>
788  { };
789 
790 #if __cplusplus >= 201402L
791 #define __cpp_lib_is_final 201402L
792  /// is_final
793  /// @since C++14
794  template<typename _Tp>
795  struct is_final
796  : public integral_constant<bool, __is_final(_Tp)>
797  { };
798 #endif
799 
800  /// is_abstract
801  template<typename _Tp>
802  struct is_abstract
803  : public integral_constant<bool, __is_abstract(_Tp)>
804  { };
805 
806  /// @cond undocumented
807  template<typename _Tp,
808  bool = is_arithmetic<_Tp>::value>
809  struct __is_signed_helper
810  : public false_type { };
811 
812  template<typename _Tp>
813  struct __is_signed_helper<_Tp, true>
814  : public integral_constant<bool, _Tp(-1) < _Tp(0)>
815  { };
816  /// @endcond
817 
818  /// is_signed
819  template<typename _Tp>
820  struct is_signed
821  : public __is_signed_helper<_Tp>::type
822  { };
823 
824  /// is_unsigned
825  template<typename _Tp>
826  struct is_unsigned
827  : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>
828  { };
829 
830  /// @cond undocumented
831  template<typename _Tp, typename _Up = _Tp&&>
832  _Up
833  __declval(int);
834 
835  template<typename _Tp>
836  _Tp
837  __declval(long);
838  /// @endcond
839 
840  template<typename _Tp>
841  auto declval() noexcept -> decltype(__declval<_Tp>(0));
842 
843  template<typename, unsigned = 0>
844  struct extent;
845 
846  template<typename>
847  struct remove_all_extents;
848 
849  /// @cond undocumented
850  template<typename _Tp>
851  struct __is_array_known_bounds
852  : public integral_constant<bool, (extent<_Tp>::value > 0)>
853  { };
854 
855  template<typename _Tp>
856  struct __is_array_unknown_bounds
857  : public __and_<is_array<_Tp>, __not_<extent<_Tp>>>
858  { };
859 
860  // Destructible and constructible type properties.
861 
862  // In N3290 is_destructible does not say anything about function
863  // types and abstract types, see LWG 2049. This implementation
864  // describes function types as non-destructible and all complete
865  // object types as destructible, iff the explicit destructor
866  // call expression is wellformed.
867  struct __do_is_destructible_impl
868  {
869  template<typename _Tp, typename = decltype(declval<_Tp&>().~_Tp())>
870  static true_type __test(int);
871 
872  template<typename>
873  static false_type __test(...);
874  };
875 
876  template<typename _Tp>
877  struct __is_destructible_impl
878  : public __do_is_destructible_impl
879  {
880  typedef decltype(__test<_Tp>(0)) type;
881  };
882 
883  template<typename _Tp,
884  bool = __or_<is_void<_Tp>,
885  __is_array_unknown_bounds<_Tp>,
886  is_function<_Tp>>::value,
887  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
888  struct __is_destructible_safe;
889 
890  template<typename _Tp>
891  struct __is_destructible_safe<_Tp, false, false>
892  : public __is_destructible_impl<typename
893  remove_all_extents<_Tp>::type>::type
894  { };
895 
896  template<typename _Tp>
897  struct __is_destructible_safe<_Tp, true, false>
898  : public false_type { };
899 
900  template<typename _Tp>
901  struct __is_destructible_safe<_Tp, false, true>
902  : public true_type { };
903  /// @endcond
904 
905  /// is_destructible
906  template<typename _Tp>
907  struct is_destructible
908  : public __is_destructible_safe<_Tp>::type
909  {
910  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
911  "template argument must be a complete class or an unbounded array");
912  };
913 
914  /// @cond undocumented
915 
916  // is_nothrow_destructible requires that is_destructible is
917  // satisfied as well. We realize that by mimicing the
918  // implementation of is_destructible but refer to noexcept(expr)
919  // instead of decltype(expr).
920  struct __do_is_nt_destructible_impl
921  {
922  template<typename _Tp>
923  static __bool_constant<noexcept(declval<_Tp&>().~_Tp())>
924  __test(int);
925 
926  template<typename>
927  static false_type __test(...);
928  };
929 
930  template<typename _Tp>
931  struct __is_nt_destructible_impl
932  : public __do_is_nt_destructible_impl
933  {
934  typedef decltype(__test<_Tp>(0)) type;
935  };
936 
937  template<typename _Tp,
938  bool = __or_<is_void<_Tp>,
939  __is_array_unknown_bounds<_Tp>,
940  is_function<_Tp>>::value,
941  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
942  struct __is_nt_destructible_safe;
943 
944  template<typename _Tp>
945  struct __is_nt_destructible_safe<_Tp, false, false>
946  : public __is_nt_destructible_impl<typename
947  remove_all_extents<_Tp>::type>::type
948  { };
949 
950  template<typename _Tp>
951  struct __is_nt_destructible_safe<_Tp, true, false>
952  : public false_type { };
953 
954  template<typename _Tp>
955  struct __is_nt_destructible_safe<_Tp, false, true>
956  : public true_type { };
957  /// @endcond
958 
959  /// is_nothrow_destructible
960  template<typename _Tp>
961  struct is_nothrow_destructible
962  : public __is_nt_destructible_safe<_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, typename... _Args>
970  struct __is_constructible_impl
971  : public __bool_constant<__is_constructible(_Tp, _Args...)>
972  { };
973  /// @endcond
974 
975  /// is_constructible
976  template<typename _Tp, typename... _Args>
977  struct is_constructible
978  : public __is_constructible_impl<_Tp, _Args...>
979  {
980  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
981  "template argument must be a complete class or an unbounded array");
982  };
983 
984  /// is_default_constructible
985  template<typename _Tp>
986  struct is_default_constructible
987  : public __is_constructible_impl<_Tp>::type
988  {
989  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
990  "template argument must be a complete class or an unbounded array");
991  };
992 
993  /// @cond undocumented
994  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
995  struct __is_copy_constructible_impl;
996 
997  template<typename _Tp>
998  struct __is_copy_constructible_impl<_Tp, false>
999  : public false_type { };
1000 
1001  template<typename _Tp>
1002  struct __is_copy_constructible_impl<_Tp, true>
1003  : public __is_constructible_impl<_Tp, const _Tp&>
1004  { };
1005  /// @endcond
1006 
1007  /// is_copy_constructible
1008  template<typename _Tp>
1009  struct is_copy_constructible
1010  : public __is_copy_constructible_impl<_Tp>
1011  {
1012  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1013  "template argument must be a complete class or an unbounded array");
1014  };
1015 
1016  /// @cond undocumented
1017  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1018  struct __is_move_constructible_impl;
1019 
1020  template<typename _Tp>
1021  struct __is_move_constructible_impl<_Tp, false>
1022  : public false_type { };
1023 
1024  template<typename _Tp>
1025  struct __is_move_constructible_impl<_Tp, true>
1026  : public __is_constructible_impl<_Tp, _Tp&&>
1027  { };
1028  /// @endcond
1029 
1030  /// is_move_constructible
1031  template<typename _Tp>
1032  struct is_move_constructible
1033  : public __is_move_constructible_impl<_Tp>
1034  {
1035  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1036  "template argument must be a complete class or an unbounded array");
1037  };
1038 
1039  /// @cond undocumented
1040  template<typename _Tp, typename... _Args>
1041  using __is_nothrow_constructible_impl
1042  = __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
1043  /// @endcond
1044 
1045  /// is_nothrow_constructible
1046  template<typename _Tp, typename... _Args>
1047  struct is_nothrow_constructible
1048  : public __is_nothrow_constructible_impl<_Tp, _Args...>::type
1049  {
1050  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1051  "template argument must be a complete class or an unbounded array");
1052  };
1053 
1054  /// is_nothrow_default_constructible
1055  template<typename _Tp>
1056  struct is_nothrow_default_constructible
1057  : public __bool_constant<__is_nothrow_constructible(_Tp)>
1058  {
1059  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1060  "template argument must be a complete class or an unbounded array");
1061  };
1062 
1063  /// @cond undocumented
1064  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1065  struct __is_nothrow_copy_constructible_impl;
1066 
1067  template<typename _Tp>
1068  struct __is_nothrow_copy_constructible_impl<_Tp, false>
1069  : public false_type { };
1070 
1071  template<typename _Tp>
1072  struct __is_nothrow_copy_constructible_impl<_Tp, true>
1073  : public __is_nothrow_constructible_impl<_Tp, const _Tp&>
1074  { };
1075  /// @endcond
1076 
1077  /// is_nothrow_copy_constructible
1078  template<typename _Tp>
1079  struct is_nothrow_copy_constructible
1080  : public __is_nothrow_copy_constructible_impl<_Tp>::type
1081  {
1082  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1083  "template argument must be a complete class or an unbounded array");
1084  };
1085 
1086  /// @cond undocumented
1087  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1088  struct __is_nothrow_move_constructible_impl;
1089 
1090  template<typename _Tp>
1091  struct __is_nothrow_move_constructible_impl<_Tp, false>
1092  : public false_type { };
1093 
1094  template<typename _Tp>
1095  struct __is_nothrow_move_constructible_impl<_Tp, true>
1096  : public __is_nothrow_constructible_impl<_Tp, _Tp&&>
1097  { };
1098  /// @endcond
1099 
1100  /// is_nothrow_move_constructible
1101  template<typename _Tp>
1102  struct is_nothrow_move_constructible
1103  : public __is_nothrow_move_constructible_impl<_Tp>::type
1104  {
1105  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1106  "template argument must be a complete class or an unbounded array");
1107  };
1108 
1109  /// is_assignable
1110  template<typename _Tp, typename _Up>
1111  struct is_assignable
1112  : public __bool_constant<__is_assignable(_Tp, _Up)>
1113  {
1114  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1115  "template argument must be a complete class or an unbounded array");
1116  };
1117 
1118  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1119  struct __is_copy_assignable_impl;
1120 
1121  template<typename _Tp>
1122  struct __is_copy_assignable_impl<_Tp, false>
1123  : public false_type { };
1124 
1125  template<typename _Tp>
1126  struct __is_copy_assignable_impl<_Tp, true>
1127  : public __bool_constant<__is_assignable(_Tp&, const _Tp&)>
1128  { };
1129 
1130  /// is_copy_assignable
1131  template<typename _Tp>
1132  struct is_copy_assignable
1133  : public __is_copy_assignable_impl<_Tp>::type
1134  {
1135  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1136  "template argument must be a complete class or an unbounded array");
1137  };
1138 
1139  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1140  struct __is_move_assignable_impl;
1141 
1142  template<typename _Tp>
1143  struct __is_move_assignable_impl<_Tp, false>
1144  : public false_type { };
1145 
1146  template<typename _Tp>
1147  struct __is_move_assignable_impl<_Tp, true>
1148  : public __bool_constant<__is_assignable(_Tp&, _Tp&&)>
1149  { };
1150 
1151  /// is_move_assignable
1152  template<typename _Tp>
1153  struct is_move_assignable
1154  : public __is_move_assignable_impl<_Tp>::type
1155  {
1156  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1157  "template argument must be a complete class or an unbounded array");
1158  };
1159 
1160  template<typename _Tp, typename _Up>
1161  using __is_nothrow_assignable_impl
1162  = __bool_constant<__is_nothrow_assignable(_Tp, _Up)>;
1163 
1164  /// is_nothrow_assignable
1165  template<typename _Tp, typename _Up>
1166  struct is_nothrow_assignable
1167  : public __is_nothrow_assignable_impl<_Tp, _Up>
1168  {
1169  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1170  "template argument must be a complete class or an unbounded array");
1171  };
1172 
1173  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1174  struct __is_nt_copy_assignable_impl;
1175 
1176  template<typename _Tp>
1177  struct __is_nt_copy_assignable_impl<_Tp, false>
1178  : public false_type { };
1179 
1180  template<typename _Tp>
1181  struct __is_nt_copy_assignable_impl<_Tp, true>
1182  : public __is_nothrow_assignable_impl<_Tp&, const _Tp&>
1183  { };
1184 
1185  /// is_nothrow_copy_assignable
1186  template<typename _Tp>
1187  struct is_nothrow_copy_assignable
1188  : public __is_nt_copy_assignable_impl<_Tp>
1189  {
1190  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1191  "template argument must be a complete class or an unbounded array");
1192  };
1193 
1194  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1195  struct __is_nt_move_assignable_impl;
1196 
1197  template<typename _Tp>
1198  struct __is_nt_move_assignable_impl<_Tp, false>
1199  : public false_type { };
1200 
1201  template<typename _Tp>
1202  struct __is_nt_move_assignable_impl<_Tp, true>
1203  : public __is_nothrow_assignable_impl<_Tp&, _Tp&&>
1204  { };
1205 
1206  /// is_nothrow_move_assignable
1207  template<typename _Tp>
1208  struct is_nothrow_move_assignable
1209  : public __is_nt_move_assignable_impl<_Tp>
1210  {
1211  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1212  "template argument must be a complete class or an unbounded array");
1213  };
1214 
1215  /// is_trivially_constructible
1216  template<typename _Tp, typename... _Args>
1217  struct is_trivially_constructible
1218  : public __bool_constant<__is_trivially_constructible(_Tp, _Args...)>
1219  {
1220  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1221  "template argument must be a complete class or an unbounded array");
1222  };
1223 
1224  /// is_trivially_default_constructible
1225  template<typename _Tp>
1226  struct is_trivially_default_constructible
1227  : public __bool_constant<__is_trivially_constructible(_Tp)>
1228  {
1229  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1230  "template argument must be a complete class or an unbounded array");
1231  };
1232 
1233  struct __do_is_implicitly_default_constructible_impl
1234  {
1235  template <typename _Tp>
1236  static void __helper(const _Tp&);
1237 
1238  template <typename _Tp>
1239  static true_type __test(const _Tp&,
1240  decltype(__helper<const _Tp&>({}))* = 0);
1241 
1242  static false_type __test(...);
1243  };
1244 
1245  template<typename _Tp>
1246  struct __is_implicitly_default_constructible_impl
1247  : public __do_is_implicitly_default_constructible_impl
1248  {
1249  typedef decltype(__test(declval<_Tp>())) type;
1250  };
1251 
1252  template<typename _Tp>
1253  struct __is_implicitly_default_constructible_safe
1254  : public __is_implicitly_default_constructible_impl<_Tp>::type
1255  { };
1256 
1257  template <typename _Tp>
1258  struct __is_implicitly_default_constructible
1259  : public __and_<__is_constructible_impl<_Tp>,
1260  __is_implicitly_default_constructible_safe<_Tp>>
1261  { };
1262 
1263  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1264  struct __is_trivially_copy_constructible_impl;
1265 
1266  template<typename _Tp>
1267  struct __is_trivially_copy_constructible_impl<_Tp, false>
1268  : public false_type { };
1269 
1270  template<typename _Tp>
1271  struct __is_trivially_copy_constructible_impl<_Tp, true>
1272  : public __and_<__is_copy_constructible_impl<_Tp>,
1273  integral_constant<bool,
1274  __is_trivially_constructible(_Tp, const _Tp&)>>
1275  { };
1276 
1277  /// is_trivially_copy_constructible
1278  template<typename _Tp>
1279  struct is_trivially_copy_constructible
1280  : public __is_trivially_copy_constructible_impl<_Tp>
1281  {
1282  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1283  "template argument must be a complete class or an unbounded array");
1284  };
1285 
1286  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1287  struct __is_trivially_move_constructible_impl;
1288 
1289  template<typename _Tp>
1290  struct __is_trivially_move_constructible_impl<_Tp, false>
1291  : public false_type { };
1292 
1293  template<typename _Tp>
1294  struct __is_trivially_move_constructible_impl<_Tp, true>
1295  : public __and_<__is_move_constructible_impl<_Tp>,
1296  integral_constant<bool,
1297  __is_trivially_constructible(_Tp, _Tp&&)>>
1298  { };
1299 
1300  /// is_trivially_move_constructible
1301  template<typename _Tp>
1302  struct is_trivially_move_constructible
1303  : public __is_trivially_move_constructible_impl<_Tp>
1304  {
1305  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1306  "template argument must be a complete class or an unbounded array");
1307  };
1308 
1309  /// is_trivially_assignable
1310  template<typename _Tp, typename _Up>
1311  struct is_trivially_assignable
1312  : public __bool_constant<__is_trivially_assignable(_Tp, _Up)>
1313  {
1314  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1315  "template argument must be a complete class or an unbounded array");
1316  };
1317 
1318  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1319  struct __is_trivially_copy_assignable_impl;
1320 
1321  template<typename _Tp>
1322  struct __is_trivially_copy_assignable_impl<_Tp, false>
1323  : public false_type { };
1324 
1325  template<typename _Tp>
1326  struct __is_trivially_copy_assignable_impl<_Tp, true>
1327  : public __bool_constant<__is_trivially_assignable(_Tp&, const _Tp&)>
1328  { };
1329 
1330  /// is_trivially_copy_assignable
1331  template<typename _Tp>
1332  struct is_trivially_copy_assignable
1333  : public __is_trivially_copy_assignable_impl<_Tp>
1334  {
1335  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1336  "template argument must be a complete class or an unbounded array");
1337  };
1338 
1339  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1340  struct __is_trivially_move_assignable_impl;
1341 
1342  template<typename _Tp>
1343  struct __is_trivially_move_assignable_impl<_Tp, false>
1344  : public false_type { };
1345 
1346  template<typename _Tp>
1347  struct __is_trivially_move_assignable_impl<_Tp, true>
1348  : public __bool_constant<__is_trivially_assignable(_Tp&, _Tp&&)>
1349  { };
1350 
1351  /// is_trivially_move_assignable
1352  template<typename _Tp>
1353  struct is_trivially_move_assignable
1354  : public __is_trivially_move_assignable_impl<_Tp>
1355  {
1356  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1357  "template argument must be a complete class or an unbounded array");
1358  };
1359 
1360  /// is_trivially_destructible
1361  template<typename _Tp>
1362  struct is_trivially_destructible
1363  : public __and_<__is_destructible_safe<_Tp>,
1364  __bool_constant<__has_trivial_destructor(_Tp)>>
1365  {
1366  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1367  "template argument must be a complete class or an unbounded array");
1368  };
1369 
1370 
1371  /// has_virtual_destructor
1372  template<typename _Tp>
1373  struct has_virtual_destructor
1374  : public integral_constant<bool, __has_virtual_destructor(_Tp)>
1375  {
1376  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1377  "template argument must be a complete class or an unbounded array");
1378  };
1379 
1380 
1381  // type property queries.
1382 
1383  /// alignment_of
1384  template<typename _Tp>
1385  struct alignment_of
1386  : public integral_constant<std::size_t, alignof(_Tp)>
1387  {
1388  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1389  "template argument must be a complete class or an unbounded array");
1390  };
1391 
1392  /// rank
1393  template<typename>
1394  struct rank
1395  : public integral_constant<std::size_t, 0> { };
1396 
1397  template<typename _Tp, std::size_t _Size>
1398  struct rank<_Tp[_Size]>
1399  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1400 
1401  template<typename _Tp>
1402  struct rank<_Tp[]>
1403  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1404 
1405  /// extent
1406  template<typename, unsigned _Uint>
1407  struct extent
1408  : public integral_constant<std::size_t, 0> { };
1409 
1410  template<typename _Tp, unsigned _Uint, std::size_t _Size>
1411  struct extent<_Tp[_Size], _Uint>
1412  : public integral_constant<std::size_t,
1413  _Uint == 0 ? _Size : extent<_Tp,
1414  _Uint - 1>::value>
1415  { };
1416 
1417  template<typename _Tp, unsigned _Uint>
1418  struct extent<_Tp[], _Uint>
1419  : public integral_constant<std::size_t,
1420  _Uint == 0 ? 0 : extent<_Tp,
1421  _Uint - 1>::value>
1422  { };
1423 
1424 
1425  // Type relations.
1426 
1427  /// is_same
1428  template<typename _Tp, typename _Up>
1429  struct is_same
1430 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1431  : public integral_constant<bool, __is_same(_Tp, _Up)>
1432 #else
1433  : public false_type
1434 #endif
1435  { };
1436 
1437 #ifndef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1438  template<typename _Tp>
1439  struct is_same<_Tp, _Tp>
1440  : public true_type
1441  { };
1442 #endif
1443 
1444  /// is_base_of
1445  template<typename _Base, typename _Derived>
1446  struct is_base_of
1447  : public integral_constant<bool, __is_base_of(_Base, _Derived)>
1448  { };
1449 
1450  template<typename _From, typename _To,
1451  bool = __or_<is_void<_From>, is_function<_To>,
1452  is_array<_To>>::value>
1453  struct __is_convertible_helper
1454  {
1455  typedef typename is_void<_To>::type type;
1456  };
1457 
1458 #pragma GCC diagnostic push
1459 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1460  template<typename _From, typename _To>
1461  class __is_convertible_helper<_From, _To, false>
1462  {
1463  template<typename _To1>
1464  static void __test_aux(_To1) noexcept;
1465 
1466  template<typename _From1, typename _To1,
1467  typename = decltype(__test_aux<_To1>(std::declval<_From1>()))>
1468  static true_type
1469  __test(int);
1470 
1471  template<typename, typename>
1472  static false_type
1473  __test(...);
1474 
1475  public:
1476  typedef decltype(__test<_From, _To>(0)) type;
1477  };
1478 #pragma GCC diagnostic pop
1479 
1480  /// is_convertible
1481  template<typename _From, typename _To>
1482  struct is_convertible
1483  : public __is_convertible_helper<_From, _To>::type
1484  { };
1485 
1486  // helper trait for unique_ptr<T[]>, shared_ptr<T[]>, and span<T, N>
1487  template<typename _ToElementType, typename _FromElementType>
1488  using __is_array_convertible
1489  = is_convertible<_FromElementType(*)[], _ToElementType(*)[]>;
1490 
1491  template<typename _From, typename _To,
1492  bool = __or_<is_void<_From>, is_function<_To>,
1493  is_array<_To>>::value>
1494  struct __is_nt_convertible_helper
1495  : is_void<_To>
1496  { };
1497 
1498 #pragma GCC diagnostic push
1499 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1500  template<typename _From, typename _To>
1501  class __is_nt_convertible_helper<_From, _To, false>
1502  {
1503  template<typename _To1>
1504  static void __test_aux(_To1) noexcept;
1505 
1506  template<typename _From1, typename _To1>
1507  static
1508  __bool_constant<noexcept(__test_aux<_To1>(std::declval<_From1>()))>
1509  __test(int);
1510 
1511  template<typename, typename>
1512  static false_type
1513  __test(...);
1514 
1515  public:
1516  using type = decltype(__test<_From, _To>(0));
1517  };
1518 #pragma GCC diagnostic pop
1519 
1520  // is_nothrow_convertible for C++11
1521  template<typename _From, typename _To>
1522  struct __is_nothrow_convertible
1523  : public __is_nt_convertible_helper<_From, _To>::type
1524  { };
1525 
1526 #if __cplusplus > 201703L
1527 #define __cpp_lib_is_nothrow_convertible 201806L
1528  /// is_nothrow_convertible
1529  template<typename _From, typename _To>
1530  struct is_nothrow_convertible
1531  : public __is_nt_convertible_helper<_From, _To>::type
1532  { };
1533 
1534  /// is_nothrow_convertible_v
1535  template<typename _From, typename _To>
1536  inline constexpr bool is_nothrow_convertible_v
1537  = is_nothrow_convertible<_From, _To>::value;
1538 #endif // C++2a
1539 
1540  // Const-volatile modifications.
1541 
1542  /// remove_const
1543  template<typename _Tp>
1544  struct remove_const
1545  { typedef _Tp type; };
1546 
1547  template<typename _Tp>
1548  struct remove_const<_Tp const>
1549  { typedef _Tp type; };
1550 
1551  /// remove_volatile
1552  template<typename _Tp>
1553  struct remove_volatile
1554  { typedef _Tp type; };
1555 
1556  template<typename _Tp>
1557  struct remove_volatile<_Tp volatile>
1558  { typedef _Tp type; };
1559 
1560  /// remove_cv
1561  template<typename _Tp>
1562  struct remove_cv
1563  { using type = _Tp; };
1564 
1565  template<typename _Tp>
1566  struct remove_cv<const _Tp>
1567  { using type = _Tp; };
1568 
1569  template<typename _Tp>
1570  struct remove_cv<volatile _Tp>
1571  { using type = _Tp; };
1572 
1573  template<typename _Tp>
1574  struct remove_cv<const volatile _Tp>
1575  { using type = _Tp; };
1576 
1577  /// add_const
1578  template<typename _Tp>
1579  struct add_const
1580  { typedef _Tp const type; };
1581 
1582  /// add_volatile
1583  template<typename _Tp>
1584  struct add_volatile
1585  { typedef _Tp volatile type; };
1586 
1587  /// add_cv
1588  template<typename _Tp>
1589  struct add_cv
1590  {
1591  typedef typename
1592  add_const<typename add_volatile<_Tp>::type>::type type;
1593  };
1594 
1595 #if __cplusplus > 201103L
1596 
1597 #define __cpp_lib_transformation_trait_aliases 201304L
1598 
1599  /// Alias template for remove_const
1600  template<typename _Tp>
1601  using remove_const_t = typename remove_const<_Tp>::type;
1602 
1603  /// Alias template for remove_volatile
1604  template<typename _Tp>
1605  using remove_volatile_t = typename remove_volatile<_Tp>::type;
1606 
1607  /// Alias template for remove_cv
1608  template<typename _Tp>
1609  using remove_cv_t = typename remove_cv<_Tp>::type;
1610 
1611  /// Alias template for add_const
1612  template<typename _Tp>
1613  using add_const_t = typename add_const<_Tp>::type;
1614 
1615  /// Alias template for add_volatile
1616  template<typename _Tp>
1617  using add_volatile_t = typename add_volatile<_Tp>::type;
1618 
1619  /// Alias template for add_cv
1620  template<typename _Tp>
1621  using add_cv_t = typename add_cv<_Tp>::type;
1622 #endif
1623 
1624  // Reference transformations.
1625 
1626  /// remove_reference
1627  template<typename _Tp>
1628  struct remove_reference
1629  { typedef _Tp type; };
1630 
1631  template<typename _Tp>
1632  struct remove_reference<_Tp&>
1633  { typedef _Tp type; };
1634 
1635  template<typename _Tp>
1636  struct remove_reference<_Tp&&>
1637  { typedef _Tp type; };
1638 
1639  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1640  struct __add_lvalue_reference_helper
1641  { typedef _Tp type; };
1642 
1643  template<typename _Tp>
1644  struct __add_lvalue_reference_helper<_Tp, true>
1645  { typedef _Tp& type; };
1646 
1647  /// add_lvalue_reference
1648  template<typename _Tp>
1649  struct add_lvalue_reference
1650  : public __add_lvalue_reference_helper<_Tp>
1651  { };
1652 
1653  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1654  struct __add_rvalue_reference_helper
1655  { typedef _Tp type; };
1656 
1657  template<typename _Tp>
1658  struct __add_rvalue_reference_helper<_Tp, true>
1659  { typedef _Tp&& type; };
1660 
1661  /// add_rvalue_reference
1662  template<typename _Tp>
1663  struct add_rvalue_reference
1664  : public __add_rvalue_reference_helper<_Tp>
1665  { };
1666 
1667 #if __cplusplus > 201103L
1668  /// Alias template for remove_reference
1669  template<typename _Tp>
1670  using remove_reference_t = typename remove_reference<_Tp>::type;
1671 
1672  /// Alias template for add_lvalue_reference
1673  template<typename _Tp>
1674  using add_lvalue_reference_t = typename add_lvalue_reference<_Tp>::type;
1675 
1676  /// Alias template for add_rvalue_reference
1677  template<typename _Tp>
1678  using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
1679 #endif
1680 
1681  // Sign modifications.
1682 
1683  /// @cond undocumented
1684 
1685  // Utility for constructing identically cv-qualified types.
1686  template<typename _Unqualified, bool _IsConst, bool _IsVol>
1687  struct __cv_selector;
1688 
1689  template<typename _Unqualified>
1690  struct __cv_selector<_Unqualified, false, false>
1691  { typedef _Unqualified __type; };
1692 
1693  template<typename _Unqualified>
1694  struct __cv_selector<_Unqualified, false, true>
1695  { typedef volatile _Unqualified __type; };
1696 
1697  template<typename _Unqualified>
1698  struct __cv_selector<_Unqualified, true, false>
1699  { typedef const _Unqualified __type; };
1700 
1701  template<typename _Unqualified>
1702  struct __cv_selector<_Unqualified, true, true>
1703  { typedef const volatile _Unqualified __type; };
1704 
1705  template<typename _Qualified, typename _Unqualified,
1706  bool _IsConst = is_const<_Qualified>::value,
1707  bool _IsVol = is_volatile<_Qualified>::value>
1708  class __match_cv_qualifiers
1709  {
1710  typedef __cv_selector<_Unqualified, _IsConst, _IsVol> __match;
1711 
1712  public:
1713  typedef typename __match::__type __type;
1714  };
1715 
1716  // Utility for finding the unsigned versions of signed integral types.
1717  template<typename _Tp>
1718  struct __make_unsigned
1719  { typedef _Tp __type; };
1720 
1721  template<>
1722  struct __make_unsigned<char>
1723  { typedef unsigned char __type; };
1724 
1725  template<>
1726  struct __make_unsigned<signed char>
1727  { typedef unsigned char __type; };
1728 
1729  template<>
1730  struct __make_unsigned<short>
1731  { typedef unsigned short __type; };
1732 
1733  template<>
1734  struct __make_unsigned<int>
1735  { typedef unsigned int __type; };
1736 
1737  template<>
1738  struct __make_unsigned<long>
1739  { typedef unsigned long __type; };
1740 
1741  template<>
1742  struct __make_unsigned<long long>
1743  { typedef unsigned long long __type; };
1744 
1745 #if defined(__GLIBCXX_TYPE_INT_N_0)
1746  __extension__
1747  template<>
1748  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_0>
1749  { typedef unsigned __GLIBCXX_TYPE_INT_N_0 __type; };
1750 #endif
1751 #if defined(__GLIBCXX_TYPE_INT_N_1)
1752  __extension__
1753  template<>
1754  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_1>
1755  { typedef unsigned __GLIBCXX_TYPE_INT_N_1 __type; };
1756 #endif
1757 #if defined(__GLIBCXX_TYPE_INT_N_2)
1758  __extension__
1759  template<>
1760  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_2>
1761  { typedef unsigned __GLIBCXX_TYPE_INT_N_2 __type; };
1762 #endif
1763 #if defined(__GLIBCXX_TYPE_INT_N_3)
1764  __extension__
1765  template<>
1766  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_3>
1767  { typedef unsigned __GLIBCXX_TYPE_INT_N_3 __type; };
1768 #endif
1769 
1770  // Select between integral and enum: not possible to be both.
1771  template<typename _Tp,
1772  bool _IsInt = is_integral<_Tp>::value,
1773  bool _IsEnum = is_enum<_Tp>::value>
1774  class __make_unsigned_selector;
1775 
1776  template<typename _Tp>
1777  class __make_unsigned_selector<_Tp, true, false>
1778  {
1779  using __unsigned_type
1780  = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
1781 
1782  public:
1783  using __type
1784  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1785  };
1786 
1787  class __make_unsigned_selector_base
1788  {
1789  protected:
1790  template<typename...> struct _List { };
1791 
1792  template<typename _Tp, typename... _Up>
1793  struct _List<_Tp, _Up...> : _List<_Up...>
1794  { static constexpr size_t __size = sizeof(_Tp); };
1795 
1796  template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
1797  struct __select;
1798 
1799  template<size_t _Sz, typename _Uint, typename... _UInts>
1800  struct __select<_Sz, _List<_Uint, _UInts...>, true>
1801  { using __type = _Uint; };
1802 
1803  template<size_t _Sz, typename _Uint, typename... _UInts>
1804  struct __select<_Sz, _List<_Uint, _UInts...>, false>
1805  : __select<_Sz, _List<_UInts...>>
1806  { };
1807  };
1808 
1809  // Choose unsigned integer type with the smallest rank and same size as _Tp
1810  template<typename _Tp>
1811  class __make_unsigned_selector<_Tp, false, true>
1812  : __make_unsigned_selector_base
1813  {
1814  // With -fshort-enums, an enum may be as small as a char.
1815  using _UInts = _List<unsigned char, unsigned short, unsigned int,
1816  unsigned long, unsigned long long>;
1817 
1818  using __unsigned_type = typename __select<sizeof(_Tp), _UInts>::__type;
1819 
1820  public:
1821  using __type
1822  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1823  };
1824 
1825  // wchar_t, char8_t, char16_t and char32_t are integral types but are
1826  // neither signed integer types nor unsigned integer types, so must be
1827  // transformed to the unsigned integer type with the smallest rank.
1828  // Use the partial specialization for enumeration types to do that.
1829  template<>
1830  struct __make_unsigned<wchar_t>
1831  {
1832  using __type
1833  = typename __make_unsigned_selector<wchar_t, false, true>::__type;
1834  };
1835 
1836 #ifdef _GLIBCXX_USE_CHAR8_T
1837  template<>
1838  struct __make_unsigned<char8_t>
1839  {
1840  using __type
1841  = typename __make_unsigned_selector<char8_t, false, true>::__type;
1842  };
1843 #endif
1844 
1845  template<>
1846  struct __make_unsigned<char16_t>
1847  {
1848  using __type
1849  = typename __make_unsigned_selector<char16_t, false, true>::__type;
1850  };
1851 
1852  template<>
1853  struct __make_unsigned<char32_t>
1854  {
1855  using __type
1856  = typename __make_unsigned_selector<char32_t, false, true>::__type;
1857  };
1858  /// @endcond
1859 
1860  // Given an integral/enum type, return the corresponding unsigned
1861  // integer type.
1862  // Primary template.
1863  /// make_unsigned
1864  template<typename _Tp>
1865  struct make_unsigned
1866  { typedef typename __make_unsigned_selector<_Tp>::__type type; };
1867 
1868  // Integral, but don't define.
1869  template<>
1870  struct make_unsigned<bool>;
1871 
1872  /// @cond undocumented
1873 
1874  // Utility for finding the signed versions of unsigned integral types.
1875  template<typename _Tp>
1876  struct __make_signed
1877  { typedef _Tp __type; };
1878 
1879  template<>
1880  struct __make_signed<char>
1881  { typedef signed char __type; };
1882 
1883  template<>
1884  struct __make_signed<unsigned char>
1885  { typedef signed char __type; };
1886 
1887  template<>
1888  struct __make_signed<unsigned short>
1889  { typedef signed short __type; };
1890 
1891  template<>
1892  struct __make_signed<unsigned int>
1893  { typedef signed int __type; };
1894 
1895  template<>
1896  struct __make_signed<unsigned long>
1897  { typedef signed long __type; };
1898 
1899  template<>
1900  struct __make_signed<unsigned long long>
1901  { typedef signed long long __type; };
1902 
1903 #if defined(__GLIBCXX_TYPE_INT_N_0)
1904  __extension__
1905  template<>
1906  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_0>
1907  { typedef __GLIBCXX_TYPE_INT_N_0 __type; };
1908 #endif
1909 #if defined(__GLIBCXX_TYPE_INT_N_1)
1910  __extension__
1911  template<>
1912  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_1>
1913  { typedef __GLIBCXX_TYPE_INT_N_1 __type; };
1914 #endif
1915 #if defined(__GLIBCXX_TYPE_INT_N_2)
1916  __extension__
1917  template<>
1918  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_2>
1919  { typedef __GLIBCXX_TYPE_INT_N_2 __type; };
1920 #endif
1921 #if defined(__GLIBCXX_TYPE_INT_N_3)
1922  __extension__
1923  template<>
1924  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_3>
1925  { typedef __GLIBCXX_TYPE_INT_N_3 __type; };
1926 #endif
1927 
1928  // Select between integral and enum: not possible to be both.
1929  template<typename _Tp,
1930  bool _IsInt = is_integral<_Tp>::value,
1931  bool _IsEnum = is_enum<_Tp>::value>
1932  class __make_signed_selector;
1933 
1934  template<typename _Tp>
1935  class __make_signed_selector<_Tp, true, false>
1936  {
1937  using __signed_type
1938  = typename __make_signed<__remove_cv_t<_Tp>>::__type;
1939 
1940  public:
1941  using __type
1942  = typename __match_cv_qualifiers<_Tp, __signed_type>::__type;
1943  };
1944 
1945  // Choose signed integer type with the smallest rank and same size as _Tp
1946  template<typename _Tp>
1947  class __make_signed_selector<_Tp, false, true>
1948  {
1949  typedef typename __make_unsigned_selector<_Tp>::__type __unsigned_type;
1950 
1951  public:
1952  typedef typename __make_signed_selector<__unsigned_type>::__type __type;
1953  };
1954 
1955  // wchar_t, char16_t and char32_t are integral types but are neither
1956  // signed integer types nor unsigned integer types, so must be
1957  // transformed to the signed integer type with the smallest rank.
1958  // Use the partial specialization for enumeration types to do that.
1959  template<>
1960  struct __make_signed<wchar_t>
1961  {
1962  using __type
1963  = typename __make_signed_selector<wchar_t, false, true>::__type;
1964  };
1965 
1966 #if defined(_GLIBCXX_USE_CHAR8_T)
1967  template<>
1968  struct __make_signed<char8_t>
1969  {
1970  using __type
1971  = typename __make_signed_selector<char8_t, false, true>::__type;
1972  };
1973 #endif
1974 
1975  template<>
1976  struct __make_signed<char16_t>
1977  {
1978  using __type
1979  = typename __make_signed_selector<char16_t, false, true>::__type;
1980  };
1981 
1982  template<>
1983  struct __make_signed<char32_t>
1984  {
1985  using __type
1986  = typename __make_signed_selector<char32_t, false, true>::__type;
1987  };
1988  /// @endcond
1989 
1990  // Given an integral/enum type, return the corresponding signed
1991  // integer type.
1992  // Primary template.
1993  /// make_signed
1994  template<typename _Tp>
1995  struct make_signed
1996  { typedef typename __make_signed_selector<_Tp>::__type type; };
1997 
1998  // Integral, but don't define.
1999  template<>
2000  struct make_signed<bool>;
2001 
2002 #if __cplusplus > 201103L
2003  /// Alias template for make_signed
2004  template<typename _Tp>
2005  using make_signed_t = typename make_signed<_Tp>::type;
2006 
2007  /// Alias template for make_unsigned
2008  template<typename _Tp>
2009  using make_unsigned_t = typename make_unsigned<_Tp>::type;
2010 #endif
2011 
2012  // Array modifications.
2013 
2014  /// remove_extent
2015  template<typename _Tp>
2016  struct remove_extent
2017  { typedef _Tp type; };
2018 
2019  template<typename _Tp, std::size_t _Size>
2020  struct remove_extent<_Tp[_Size]>
2021  { typedef _Tp type; };
2022 
2023  template<typename _Tp>
2024  struct remove_extent<_Tp[]>
2025  { typedef _Tp type; };
2026 
2027  /// remove_all_extents
2028  template<typename _Tp>
2029  struct remove_all_extents
2030  { typedef _Tp type; };
2031 
2032  template<typename _Tp, std::size_t _Size>
2033  struct remove_all_extents<_Tp[_Size]>
2034  { typedef typename remove_all_extents<_Tp>::type type; };
2035 
2036  template<typename _Tp>
2037  struct remove_all_extents<_Tp[]>
2038  { typedef typename remove_all_extents<_Tp>::type type; };
2039 
2040 #if __cplusplus > 201103L
2041  /// Alias template for remove_extent
2042  template<typename _Tp>
2043  using remove_extent_t = typename remove_extent<_Tp>::type;
2044 
2045  /// Alias template for remove_all_extents
2046  template<typename _Tp>
2047  using remove_all_extents_t = typename remove_all_extents<_Tp>::type;
2048 #endif
2049 
2050  // Pointer modifications.
2051 
2052  template<typename _Tp, typename>
2053  struct __remove_pointer_helper
2054  { typedef _Tp type; };
2055 
2056  template<typename _Tp, typename _Up>
2057  struct __remove_pointer_helper<_Tp, _Up*>
2058  { typedef _Up type; };
2059 
2060  /// remove_pointer
2061  template<typename _Tp>
2062  struct remove_pointer
2063  : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
2064  { };
2065 
2066  template<typename _Tp, bool = __or_<__is_referenceable<_Tp>,
2067  is_void<_Tp>>::value>
2068  struct __add_pointer_helper
2069  { typedef _Tp type; };
2070 
2071  template<typename _Tp>
2072  struct __add_pointer_helper<_Tp, true>
2073  { typedef typename remove_reference<_Tp>::type* type; };
2074 
2075  /// add_pointer
2076  template<typename _Tp>
2077  struct add_pointer
2078  : public __add_pointer_helper<_Tp>
2079  { };
2080 
2081 #if __cplusplus > 201103L
2082  /// Alias template for remove_pointer
2083  template<typename _Tp>
2084  using remove_pointer_t = typename remove_pointer<_Tp>::type;
2085 
2086  /// Alias template for add_pointer
2087  template<typename _Tp>
2088  using add_pointer_t = typename add_pointer<_Tp>::type;
2089 #endif
2090 
2091  template<std::size_t _Len>
2092  struct __aligned_storage_msa
2093  {
2094  union __type
2095  {
2096  unsigned char __data[_Len];
2097  struct __attribute__((__aligned__)) { } __align;
2098  };
2099  };
2100 
2101  /**
2102  * @brief Alignment type.
2103  *
2104  * The value of _Align is a default-alignment which shall be the
2105  * most stringent alignment requirement for any C++ object type
2106  * whose size is no greater than _Len (3.9). The member typedef
2107  * type shall be a POD type suitable for use as uninitialized
2108  * storage for any object whose size is at most _Len and whose
2109  * alignment is a divisor of _Align.
2110  */
2111  template<std::size_t _Len, std::size_t _Align =
2112  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2113  struct aligned_storage
2114  {
2115  union type
2116  {
2117  unsigned char __data[_Len];
2118  struct __attribute__((__aligned__((_Align)))) { } __align;
2119  };
2120  };
2121 
2122  template <typename... _Types>
2123  struct __strictest_alignment
2124  {
2125  static const size_t _S_alignment = 0;
2126  static const size_t _S_size = 0;
2127  };
2128 
2129  template <typename _Tp, typename... _Types>
2130  struct __strictest_alignment<_Tp, _Types...>
2131  {
2132  static const size_t _S_alignment =
2133  alignof(_Tp) > __strictest_alignment<_Types...>::_S_alignment
2134  ? alignof(_Tp) : __strictest_alignment<_Types...>::_S_alignment;
2135  static const size_t _S_size =
2136  sizeof(_Tp) > __strictest_alignment<_Types...>::_S_size
2137  ? sizeof(_Tp) : __strictest_alignment<_Types...>::_S_size;
2138  };
2139 
2140  /**
2141  * @brief Provide aligned storage for types.
2142  *
2143  * [meta.trans.other]
2144  *
2145  * Provides aligned storage for any of the provided types of at
2146  * least size _Len.
2147  *
2148  * @see aligned_storage
2149  */
2150  template <size_t _Len, typename... _Types>
2151  struct aligned_union
2152  {
2153  private:
2154  static_assert(sizeof...(_Types) != 0, "At least one type is required");
2155 
2156  using __strictest = __strictest_alignment<_Types...>;
2157  static const size_t _S_len = _Len > __strictest::_S_size
2158  ? _Len : __strictest::_S_size;
2159  public:
2160  /// The value of the strictest alignment of _Types.
2161  static const size_t alignment_value = __strictest::_S_alignment;
2162  /// The storage.
2163  typedef typename aligned_storage<_S_len, alignment_value>::type type;
2164  };
2165 
2166  template <size_t _Len, typename... _Types>
2167  const size_t aligned_union<_Len, _Types...>::alignment_value;
2168 
2169  /// @cond undocumented
2170 
2171  // Decay trait for arrays and functions, used for perfect forwarding
2172  // in make_pair, make_tuple, etc.
2173  template<typename _Up,
2174  bool _IsArray = is_array<_Up>::value,
2175  bool _IsFunction = is_function<_Up>::value>
2176  struct __decay_selector;
2177 
2178  // NB: DR 705.
2179  template<typename _Up>
2180  struct __decay_selector<_Up, false, false>
2181  { typedef __remove_cv_t<_Up> __type; };
2182 
2183  template<typename _Up>
2184  struct __decay_selector<_Up, true, false>
2185  { typedef typename remove_extent<_Up>::type* __type; };
2186 
2187  template<typename _Up>
2188  struct __decay_selector<_Up, false, true>
2189  { typedef typename add_pointer<_Up>::type __type; };
2190  /// @endcond
2191 
2192  /// decay
2193  template<typename _Tp>
2194  class decay
2195  {
2196  typedef typename remove_reference<_Tp>::type __remove_type;
2197 
2198  public:
2199  typedef typename __decay_selector<__remove_type>::__type type;
2200  };
2201 
2202  /// @cond undocumented
2203 
2204  // Helper which adds a reference to a type when given a reference_wrapper
2205  template<typename _Tp>
2206  struct __strip_reference_wrapper
2207  {
2208  typedef _Tp __type;
2209  };
2210 
2211  template<typename _Tp>
2212  struct __strip_reference_wrapper<reference_wrapper<_Tp> >
2213  {
2214  typedef _Tp& __type;
2215  };
2216 
2217  // __decay_t (std::decay_t for C++11).
2218  template<typename _Tp>
2219  using __decay_t = typename decay<_Tp>::type;
2220 
2221  template<typename _Tp>
2222  using __decay_and_strip = __strip_reference_wrapper<__decay_t<_Tp>>;
2223  /// @endcond
2224 
2225  // Primary template.
2226  /// Define a member typedef `type` only if a boolean constant is true.
2227  template<bool, typename _Tp = void>
2228  struct enable_if
2229  { };
2230 
2231  // Partial specialization for true.
2232  template<typename _Tp>
2233  struct enable_if<true, _Tp>
2234  { typedef _Tp type; };
2235 
2236  /// @cond undocumented
2237 
2238  // __enable_if_t (std::enable_if_t for C++11)
2239  template<bool _Cond, typename _Tp = void>
2240  using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
2241 
2242  // Helper for SFINAE constraints
2243  template<typename... _Cond>
2244  using _Require = __enable_if_t<__and_<_Cond...>::value>;
2245 
2246  // __remove_cvref_t (std::remove_cvref_t for C++11).
2247  template<typename _Tp>
2248  using __remove_cvref_t
2249  = typename remove_cv<typename remove_reference<_Tp>::type>::type;
2250  /// @endcond
2251 
2252  // Primary template.
2253  /// Define a member typedef @c type to one of two argument types.
2254  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2255  struct conditional
2256  { typedef _Iftrue type; };
2257 
2258  // Partial specialization for false.
2259  template<typename _Iftrue, typename _Iffalse>
2260  struct conditional<false, _Iftrue, _Iffalse>
2261  { typedef _Iffalse type; };
2262 
2263  /// common_type
2264  template<typename... _Tp>
2265  struct common_type;
2266 
2267  // Sfinae-friendly common_type implementation:
2268 
2269  /// @cond undocumented
2270  struct __do_common_type_impl
2271  {
2272  template<typename _Tp, typename _Up>
2273  using __cond_t
2274  = decltype(true ? std::declval<_Tp>() : std::declval<_Up>());
2275 
2276  // if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2277  // denotes a valid type, let C denote that type.
2278  template<typename _Tp, typename _Up>
2279  static __success_type<__decay_t<__cond_t<_Tp, _Up>>>
2280  _S_test(int);
2281 
2282 #if __cplusplus > 201703L
2283  // Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type,
2284  // let C denote the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
2285  template<typename _Tp, typename _Up>
2286  static __success_type<__remove_cvref_t<__cond_t<const _Tp&, const _Up&>>>
2287  _S_test_2(int);
2288 #endif
2289 
2290  template<typename, typename>
2291  static __failure_type
2292  _S_test_2(...);
2293 
2294  template<typename _Tp, typename _Up>
2295  static decltype(_S_test_2<_Tp, _Up>(0))
2296  _S_test(...);
2297  };
2298 
2299  // If sizeof...(T) is zero, there shall be no member type.
2300  template<>
2301  struct common_type<>
2302  { };
2303 
2304  // If sizeof...(T) is one, the same type, if any, as common_type_t<T0, T0>.
2305  template<typename _Tp0>
2306  struct common_type<_Tp0>
2307  : public common_type<_Tp0, _Tp0>
2308  { };
2309 
2310  // If sizeof...(T) is two, ...
2311  template<typename _Tp1, typename _Tp2,
2312  typename _Dp1 = __decay_t<_Tp1>, typename _Dp2 = __decay_t<_Tp2>>
2313  struct __common_type_impl
2314  {
2315  // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false,
2316  // let C denote the same type, if any, as common_type_t<D1, D2>.
2317  using type = common_type<_Dp1, _Dp2>;
2318  };
2319 
2320  template<typename _Tp1, typename _Tp2>
2321  struct __common_type_impl<_Tp1, _Tp2, _Tp1, _Tp2>
2322  : private __do_common_type_impl
2323  {
2324  // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2325  // denotes a valid type, let C denote that type.
2326  using type = decltype(_S_test<_Tp1, _Tp2>(0));
2327  };
2328 
2329  // If sizeof...(T) is two, ...
2330  template<typename _Tp1, typename _Tp2>
2331  struct common_type<_Tp1, _Tp2>
2332  : public __common_type_impl<_Tp1, _Tp2>::type
2333  { };
2334 
2335  template<typename...>
2336  struct __common_type_pack
2337  { };
2338 
2339  template<typename, typename, typename = void>
2340  struct __common_type_fold;
2341 
2342  // If sizeof...(T) is greater than two, ...
2343  template<typename _Tp1, typename _Tp2, typename... _Rp>
2344  struct common_type<_Tp1, _Tp2, _Rp...>
2345  : public __common_type_fold<common_type<_Tp1, _Tp2>,
2346  __common_type_pack<_Rp...>>
2347  { };
2348 
2349  // Let C denote the same type, if any, as common_type_t<T1, T2>.
2350  // If there is such a type C, type shall denote the same type, if any,
2351  // as common_type_t<C, R...>.
2352  template<typename _CTp, typename... _Rp>
2353  struct __common_type_fold<_CTp, __common_type_pack<_Rp...>,
2354  __void_t<typename _CTp::type>>
2355  : public common_type<typename _CTp::type, _Rp...>
2356  { };
2357 
2358  // Otherwise, there shall be no member type.
2359  template<typename _CTp, typename _Rp>
2360  struct __common_type_fold<_CTp, _Rp, void>
2361  { };
2362 
2363  template<typename _Tp, bool = is_enum<_Tp>::value>
2364  struct __underlying_type_impl
2365  {
2366  using type = __underlying_type(_Tp);
2367  };
2368 
2369  template<typename _Tp>
2370  struct __underlying_type_impl<_Tp, false>
2371  { };
2372  /// @endcond
2373 
2374  /// The underlying type of an enum.
2375  template<typename _Tp>
2376  struct underlying_type
2377  : public __underlying_type_impl<_Tp>
2378  { };
2379 
2380  /// @cond undocumented
2381  template<typename _Tp>
2382  struct __declval_protector
2383  {
2384  static const bool __stop = false;
2385  };
2386  /// @endcond
2387 
2388  /** Utility to simplify expressions used in unevaluated operands
2389  * @since C++11
2390  * @ingroup utilities
2391  */
2392  template<typename _Tp>
2393  auto declval() noexcept -> decltype(__declval<_Tp>(0))
2394  {
2395  static_assert(__declval_protector<_Tp>::__stop,
2396  "declval() must not be used!");
2397  return __declval<_Tp>(0);
2398  }
2399 
2400  /// result_of
2401  template<typename _Signature>
2402  struct result_of;
2403 
2404  // Sfinae-friendly result_of implementation:
2405 
2406 #define __cpp_lib_result_of_sfinae 201210L
2407 
2408  /// @cond undocumented
2409  struct __invoke_memfun_ref { };
2410  struct __invoke_memfun_deref { };
2411  struct __invoke_memobj_ref { };
2412  struct __invoke_memobj_deref { };
2413  struct __invoke_other { };
2414 
2415  // Associate a tag type with a specialization of __success_type.
2416  template<typename _Tp, typename _Tag>
2417  struct __result_of_success : __success_type<_Tp>
2418  { using __invoke_type = _Tag; };
2419 
2420  // [func.require] paragraph 1 bullet 1:
2421  struct __result_of_memfun_ref_impl
2422  {
2423  template<typename _Fp, typename _Tp1, typename... _Args>
2424  static __result_of_success<decltype(
2425  (std::declval<_Tp1>().*std::declval<_Fp>())(std::declval<_Args>()...)
2426  ), __invoke_memfun_ref> _S_test(int);
2427 
2428  template<typename...>
2429  static __failure_type _S_test(...);
2430  };
2431 
2432  template<typename _MemPtr, typename _Arg, typename... _Args>
2433  struct __result_of_memfun_ref
2434  : private __result_of_memfun_ref_impl
2435  {
2436  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2437  };
2438 
2439  // [func.require] paragraph 1 bullet 2:
2440  struct __result_of_memfun_deref_impl
2441  {
2442  template<typename _Fp, typename _Tp1, typename... _Args>
2443  static __result_of_success<decltype(
2444  ((*std::declval<_Tp1>()).*std::declval<_Fp>())(std::declval<_Args>()...)
2445  ), __invoke_memfun_deref> _S_test(int);
2446 
2447  template<typename...>
2448  static __failure_type _S_test(...);
2449  };
2450 
2451  template<typename _MemPtr, typename _Arg, typename... _Args>
2452  struct __result_of_memfun_deref
2453  : private __result_of_memfun_deref_impl
2454  {
2455  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2456  };
2457 
2458  // [func.require] paragraph 1 bullet 3:
2459  struct __result_of_memobj_ref_impl
2460  {
2461  template<typename _Fp, typename _Tp1>
2462  static __result_of_success<decltype(
2463  std::declval<_Tp1>().*std::declval<_Fp>()
2464  ), __invoke_memobj_ref> _S_test(int);
2465 
2466  template<typename, typename>
2467  static __failure_type _S_test(...);
2468  };
2469 
2470  template<typename _MemPtr, typename _Arg>
2471  struct __result_of_memobj_ref
2472  : private __result_of_memobj_ref_impl
2473  {
2474  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2475  };
2476 
2477  // [func.require] paragraph 1 bullet 4:
2478  struct __result_of_memobj_deref_impl
2479  {
2480  template<typename _Fp, typename _Tp1>
2481  static __result_of_success<decltype(
2482  (*std::declval<_Tp1>()).*std::declval<_Fp>()
2483  ), __invoke_memobj_deref> _S_test(int);
2484 
2485  template<typename, typename>
2486  static __failure_type _S_test(...);
2487  };
2488 
2489  template<typename _MemPtr, typename _Arg>
2490  struct __result_of_memobj_deref
2491  : private __result_of_memobj_deref_impl
2492  {
2493  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2494  };
2495 
2496  template<typename _MemPtr, typename _Arg>
2497  struct __result_of_memobj;
2498 
2499  template<typename _Res, typename _Class, typename _Arg>
2500  struct __result_of_memobj<_Res _Class::*, _Arg>
2501  {
2502  typedef __remove_cvref_t<_Arg> _Argval;
2503  typedef _Res _Class::* _MemPtr;
2504  typedef typename __conditional_t<__or_<is_same<_Argval, _Class>,
2505  is_base_of<_Class, _Argval>>::value,
2506  __result_of_memobj_ref<_MemPtr, _Arg>,
2507  __result_of_memobj_deref<_MemPtr, _Arg>
2508  >::type type;
2509  };
2510 
2511  template<typename _MemPtr, typename _Arg, typename... _Args>
2512  struct __result_of_memfun;
2513 
2514  template<typename _Res, typename _Class, typename _Arg, typename... _Args>
2515  struct __result_of_memfun<_Res _Class::*, _Arg, _Args...>
2516  {
2517  typedef typename remove_reference<_Arg>::type _Argval;
2518  typedef _Res _Class::* _MemPtr;
2519  typedef typename __conditional_t<is_base_of<_Class, _Argval>::value,
2520  __result_of_memfun_ref<_MemPtr, _Arg, _Args...>,
2521  __result_of_memfun_deref<_MemPtr, _Arg, _Args...>
2522  >::type type;
2523  };
2524 
2525  // _GLIBCXX_RESOLVE_LIB_DEFECTS
2526  // 2219. INVOKE-ing a pointer to member with a reference_wrapper
2527  // as the object expression
2528 
2529  // Used by result_of, invoke etc. to unwrap a reference_wrapper.
2530  template<typename _Tp, typename _Up = __remove_cvref_t<_Tp>>
2531  struct __inv_unwrap
2532  {
2533  using type = _Tp;
2534  };
2535 
2536  template<typename _Tp, typename _Up>
2537  struct __inv_unwrap<_Tp, reference_wrapper<_Up>>
2538  {
2539  using type = _Up&;
2540  };
2541 
2542  template<bool, bool, typename _Functor, typename... _ArgTypes>
2543  struct __result_of_impl
2544  {
2545  typedef __failure_type type;
2546  };
2547 
2548  template<typename _MemPtr, typename _Arg>
2549  struct __result_of_impl<true, false, _MemPtr, _Arg>
2550  : public __result_of_memobj<__decay_t<_MemPtr>,
2551  typename __inv_unwrap<_Arg>::type>
2552  { };
2553 
2554  template<typename _MemPtr, typename _Arg, typename... _Args>
2555  struct __result_of_impl<false, true, _MemPtr, _Arg, _Args...>
2556  : public __result_of_memfun<__decay_t<_MemPtr>,
2557  typename __inv_unwrap<_Arg>::type, _Args...>
2558  { };
2559 
2560  // [func.require] paragraph 1 bullet 5:
2561  struct __result_of_other_impl
2562  {
2563  template<typename _Fn, typename... _Args>
2564  static __result_of_success<decltype(
2565  std::declval<_Fn>()(std::declval<_Args>()...)
2566  ), __invoke_other> _S_test(int);
2567 
2568  template<typename...>
2569  static __failure_type _S_test(...);
2570  };
2571 
2572  template<typename _Functor, typename... _ArgTypes>
2573  struct __result_of_impl<false, false, _Functor, _ArgTypes...>
2574  : private __result_of_other_impl
2575  {
2576  typedef decltype(_S_test<_Functor, _ArgTypes...>(0)) type;
2577  };
2578 
2579  // __invoke_result (std::invoke_result for C++11)
2580  template<typename _Functor, typename... _ArgTypes>
2581  struct __invoke_result
2582  : public __result_of_impl<
2583  is_member_object_pointer<
2584  typename remove_reference<_Functor>::type
2585  >::value,
2586  is_member_function_pointer<
2587  typename remove_reference<_Functor>::type
2588  >::value,
2589  _Functor, _ArgTypes...
2590  >::type
2591  { };
2592  /// @endcond
2593 
2594  template<typename _Functor, typename... _ArgTypes>
2595  struct result_of<_Functor(_ArgTypes...)>
2596  : public __invoke_result<_Functor, _ArgTypes...>
2597  { } _GLIBCXX17_DEPRECATED_SUGGEST("std::invoke_result");
2598 
2599 #if __cplusplus >= 201402L
2600  /// Alias template for aligned_storage
2601  template<size_t _Len, size_t _Align =
2602  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2603  using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
2604 
2605  template <size_t _Len, typename... _Types>
2606  using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
2607 
2608  /// Alias template for decay
2609  template<typename _Tp>
2610  using decay_t = typename decay<_Tp>::type;
2611 
2612  /// Alias template for enable_if
2613  template<bool _Cond, typename _Tp = void>
2614  using enable_if_t = typename enable_if<_Cond, _Tp>::type;
2615 
2616  /// Alias template for conditional
2617  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2618  using conditional_t = typename conditional<_Cond, _Iftrue, _Iffalse>::type;
2619 
2620  /// Alias template for common_type
2621  template<typename... _Tp>
2622  using common_type_t = typename common_type<_Tp...>::type;
2623 
2624  /// Alias template for underlying_type
2625  template<typename _Tp>
2626  using underlying_type_t = typename underlying_type<_Tp>::type;
2627 
2628  /// Alias template for result_of
2629  template<typename _Tp>
2630  using result_of_t = typename result_of<_Tp>::type;
2631 #endif // C++14
2632 
2633 #if __cplusplus >= 201703L || !defined(__STRICT_ANSI__) // c++17 or gnu++11
2634 #define __cpp_lib_void_t 201411L
2635  /// A metafunction that always yields void, used for detecting valid types.
2636  template<typename...> using void_t = void;
2637 #endif
2638 
2639  /// @cond undocumented
2640 
2641  /// Implementation of the detection idiom (negative case).
2642  template<typename _Default, typename _AlwaysVoid,
2643  template<typename...> class _Op, typename... _Args>
2644  struct __detector
2645  {
2646  using value_t = false_type;
2647  using type = _Default;
2648  };
2649 
2650  /// Implementation of the detection idiom (positive case).
2651  template<typename _Default, template<typename...> class _Op,
2652  typename... _Args>
2653  struct __detector<_Default, __void_t<_Op<_Args...>>, _Op, _Args...>
2654  {
2655  using value_t = true_type;
2656  using type = _Op<_Args...>;
2657  };
2658 
2659  // Detect whether _Op<_Args...> is a valid type, use _Default if not.
2660  template<typename _Default, template<typename...> class _Op,
2661  typename... _Args>
2662  using __detected_or = __detector<_Default, void, _Op, _Args...>;
2663 
2664  // _Op<_Args...> if that is a valid type, otherwise _Default.
2665  template<typename _Default, template<typename...> class _Op,
2666  typename... _Args>
2667  using __detected_or_t
2668  = typename __detected_or<_Default, _Op, _Args...>::type;
2669 
2670  /**
2671  * Use SFINAE to determine if the type _Tp has a publicly-accessible
2672  * member type _NTYPE.
2673  */
2674 #define _GLIBCXX_HAS_NESTED_TYPE(_NTYPE) \
2675  template<typename _Tp, typename = __void_t<>> \
2676  struct __has_##_NTYPE \
2677  : false_type \
2678  { }; \
2679  template<typename _Tp> \
2680  struct __has_##_NTYPE<_Tp, __void_t<typename _Tp::_NTYPE>> \
2681  : true_type \
2682  { };
2683 
2684  template <typename _Tp>
2685  struct __is_swappable;
2686 
2687  template <typename _Tp>
2688  struct __is_nothrow_swappable;
2689 
2690  template<typename>
2691  struct __is_tuple_like_impl : false_type
2692  { };
2693 
2694  // Internal type trait that allows us to sfinae-protect tuple_cat.
2695  template<typename _Tp>
2696  struct __is_tuple_like
2697  : public __is_tuple_like_impl<__remove_cvref_t<_Tp>>::type
2698  { };
2699  /// @endcond
2700 
2701  template<typename _Tp>
2702  _GLIBCXX20_CONSTEXPR
2703  inline
2704  _Require<__not_<__is_tuple_like<_Tp>>,
2705  is_move_constructible<_Tp>,
2706  is_move_assignable<_Tp>>
2707  swap(_Tp&, _Tp&)
2708  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
2709  is_nothrow_move_assignable<_Tp>>::value);
2710 
2711  template<typename _Tp, size_t _Nm>
2712  _GLIBCXX20_CONSTEXPR
2713  inline
2714  __enable_if_t<__is_swappable<_Tp>::value>
2715  swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
2716  noexcept(__is_nothrow_swappable<_Tp>::value);
2717 
2718  /// @cond undocumented
2719  namespace __swappable_details {
2720  using std::swap;
2721 
2722  struct __do_is_swappable_impl
2723  {
2724  template<typename _Tp, typename
2725  = decltype(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))>
2726  static true_type __test(int);
2727 
2728  template<typename>
2729  static false_type __test(...);
2730  };
2731 
2732  struct __do_is_nothrow_swappable_impl
2733  {
2734  template<typename _Tp>
2735  static __bool_constant<
2736  noexcept(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))
2737  > __test(int);
2738 
2739  template<typename>
2740  static false_type __test(...);
2741  };
2742 
2743  } // namespace __swappable_details
2744 
2745  template<typename _Tp>
2746  struct __is_swappable_impl
2747  : public __swappable_details::__do_is_swappable_impl
2748  {
2749  typedef decltype(__test<_Tp>(0)) type;
2750  };
2751 
2752  template<typename _Tp>
2753  struct __is_nothrow_swappable_impl
2754  : public __swappable_details::__do_is_nothrow_swappable_impl
2755  {
2756  typedef decltype(__test<_Tp>(0)) type;
2757  };
2758 
2759  template<typename _Tp>
2760  struct __is_swappable
2761  : public __is_swappable_impl<_Tp>::type
2762  { };
2763 
2764  template<typename _Tp>
2765  struct __is_nothrow_swappable
2766  : public __is_nothrow_swappable_impl<_Tp>::type
2767  { };
2768  /// @endcond
2769 
2770 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2771 #define __cpp_lib_is_swappable 201603L
2772  /// Metafunctions used for detecting swappable types: p0185r1
2773 
2774  /// is_swappable
2775  template<typename _Tp>
2776  struct is_swappable
2777  : public __is_swappable_impl<_Tp>::type
2778  {
2779  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2780  "template argument must be a complete class or an unbounded array");
2781  };
2782 
2783  /// is_nothrow_swappable
2784  template<typename _Tp>
2785  struct is_nothrow_swappable
2786  : public __is_nothrow_swappable_impl<_Tp>::type
2787  {
2788  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2789  "template argument must be a complete class or an unbounded array");
2790  };
2791 
2792 #if __cplusplus >= 201402L
2793  /// is_swappable_v
2794  template<typename _Tp>
2795  _GLIBCXX17_INLINE constexpr bool is_swappable_v =
2796  is_swappable<_Tp>::value;
2797 
2798  /// is_nothrow_swappable_v
2799  template<typename _Tp>
2800  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_v =
2801  is_nothrow_swappable<_Tp>::value;
2802 #endif // __cplusplus >= 201402L
2803 
2804  /// @cond undocumented
2805  namespace __swappable_with_details {
2806  using std::swap;
2807 
2808  struct __do_is_swappable_with_impl
2809  {
2810  template<typename _Tp, typename _Up, typename
2811  = decltype(swap(std::declval<_Tp>(), std::declval<_Up>())),
2812  typename
2813  = decltype(swap(std::declval<_Up>(), std::declval<_Tp>()))>
2814  static true_type __test(int);
2815 
2816  template<typename, typename>
2817  static false_type __test(...);
2818  };
2819 
2820  struct __do_is_nothrow_swappable_with_impl
2821  {
2822  template<typename _Tp, typename _Up>
2823  static __bool_constant<
2824  noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()))
2825  &&
2826  noexcept(swap(std::declval<_Up>(), std::declval<_Tp>()))
2827  > __test(int);
2828 
2829  template<typename, typename>
2830  static false_type __test(...);
2831  };
2832 
2833  } // namespace __swappable_with_details
2834 
2835  template<typename _Tp, typename _Up>
2836  struct __is_swappable_with_impl
2837  : public __swappable_with_details::__do_is_swappable_with_impl
2838  {
2839  typedef decltype(__test<_Tp, _Up>(0)) type;
2840  };
2841 
2842  // Optimization for the homogenous lvalue case, not required:
2843  template<typename _Tp>
2844  struct __is_swappable_with_impl<_Tp&, _Tp&>
2845  : public __swappable_details::__do_is_swappable_impl
2846  {
2847  typedef decltype(__test<_Tp&>(0)) type;
2848  };
2849 
2850  template<typename _Tp, typename _Up>
2851  struct __is_nothrow_swappable_with_impl
2852  : public __swappable_with_details::__do_is_nothrow_swappable_with_impl
2853  {
2854  typedef decltype(__test<_Tp, _Up>(0)) type;
2855  };
2856 
2857  // Optimization for the homogenous lvalue case, not required:
2858  template<typename _Tp>
2859  struct __is_nothrow_swappable_with_impl<_Tp&, _Tp&>
2860  : public __swappable_details::__do_is_nothrow_swappable_impl
2861  {
2862  typedef decltype(__test<_Tp&>(0)) type;
2863  };
2864  /// @endcond
2865 
2866  /// is_swappable_with
2867  template<typename _Tp, typename _Up>
2868  struct is_swappable_with
2869  : public __is_swappable_with_impl<_Tp, _Up>::type
2870  {
2871  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2872  "first template argument must be a complete class or an unbounded array");
2873  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2874  "second template argument must be a complete class or an unbounded array");
2875  };
2876 
2877  /// is_nothrow_swappable_with
2878  template<typename _Tp, typename _Up>
2879  struct is_nothrow_swappable_with
2880  : public __is_nothrow_swappable_with_impl<_Tp, _Up>::type
2881  {
2882  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2883  "first template argument must be a complete class or an unbounded array");
2884  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2885  "second template argument must be a complete class or an unbounded array");
2886  };
2887 
2888 #if __cplusplus >= 201402L
2889  /// is_swappable_with_v
2890  template<typename _Tp, typename _Up>
2891  _GLIBCXX17_INLINE constexpr bool is_swappable_with_v =
2892  is_swappable_with<_Tp, _Up>::value;
2893 
2894  /// is_nothrow_swappable_with_v
2895  template<typename _Tp, typename _Up>
2896  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_with_v =
2897  is_nothrow_swappable_with<_Tp, _Up>::value;
2898 #endif // __cplusplus >= 201402L
2899 
2900 #endif// c++1z or gnu++11
2901 
2902  /// @cond undocumented
2903 
2904  // __is_invocable (std::is_invocable for C++11)
2905 
2906  // The primary template is used for invalid INVOKE expressions.
2907  template<typename _Result, typename _Ret,
2908  bool = is_void<_Ret>::value, typename = void>
2909  struct __is_invocable_impl : false_type { };
2910 
2911  // Used for valid INVOKE and INVOKE<void> expressions.
2912  template<typename _Result, typename _Ret>
2913  struct __is_invocable_impl<_Result, _Ret,
2914  /* is_void<_Ret> = */ true,
2915  __void_t<typename _Result::type>>
2916  : true_type
2917  { };
2918 
2919 #pragma GCC diagnostic push
2920 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
2921  // Used for INVOKE<R> expressions to check the implicit conversion to R.
2922  template<typename _Result, typename _Ret>
2923  struct __is_invocable_impl<_Result, _Ret,
2924  /* is_void<_Ret> = */ false,
2925  __void_t<typename _Result::type>>
2926  {
2927  private:
2928  // The type of the INVOKE expression.
2929  // Unlike declval, this doesn't add_rvalue_reference.
2930  static typename _Result::type _S_get();
2931 
2932  template<typename _Tp>
2933  static void _S_conv(_Tp);
2934 
2935  // This overload is viable if INVOKE(f, args...) can convert to _Tp.
2936  template<typename _Tp, typename = decltype(_S_conv<_Tp>(_S_get()))>
2937  static true_type
2938  _S_test(int);
2939 
2940  template<typename _Tp>
2941  static false_type
2942  _S_test(...);
2943 
2944  public:
2945  using type = decltype(_S_test<_Ret>(1));
2946  };
2947 #pragma GCC diagnostic pop
2948 
2949  template<typename _Fn, typename... _ArgTypes>
2950  struct __is_invocable
2951  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
2952  { };
2953 
2954  template<typename _Fn, typename _Tp, typename... _Args>
2955  constexpr bool __call_is_nt(__invoke_memfun_ref)
2956  {
2957  using _Up = typename __inv_unwrap<_Tp>::type;
2958  return noexcept((std::declval<_Up>().*std::declval<_Fn>())(
2959  std::declval<_Args>()...));
2960  }
2961 
2962  template<typename _Fn, typename _Tp, typename... _Args>
2963  constexpr bool __call_is_nt(__invoke_memfun_deref)
2964  {
2965  return noexcept(((*std::declval<_Tp>()).*std::declval<_Fn>())(
2966  std::declval<_Args>()...));
2967  }
2968 
2969  template<typename _Fn, typename _Tp>
2970  constexpr bool __call_is_nt(__invoke_memobj_ref)
2971  {
2972  using _Up = typename __inv_unwrap<_Tp>::type;
2973  return noexcept(std::declval<_Up>().*std::declval<_Fn>());
2974  }
2975 
2976  template<typename _Fn, typename _Tp>
2977  constexpr bool __call_is_nt(__invoke_memobj_deref)
2978  {
2979  return noexcept((*std::declval<_Tp>()).*std::declval<_Fn>());
2980  }
2981 
2982  template<typename _Fn, typename... _Args>
2983  constexpr bool __call_is_nt(__invoke_other)
2984  {
2985  return noexcept(std::declval<_Fn>()(std::declval<_Args>()...));
2986  }
2987 
2988  template<typename _Result, typename _Fn, typename... _Args>
2989  struct __call_is_nothrow
2990  : __bool_constant<
2991  std::__call_is_nt<_Fn, _Args...>(typename _Result::__invoke_type{})
2992  >
2993  { };
2994 
2995  template<typename _Fn, typename... _Args>
2996  using __call_is_nothrow_
2997  = __call_is_nothrow<__invoke_result<_Fn, _Args...>, _Fn, _Args...>;
2998 
2999  // __is_nothrow_invocable (std::is_nothrow_invocable for C++11)
3000  template<typename _Fn, typename... _Args>
3001  struct __is_nothrow_invocable
3002  : __and_<__is_invocable<_Fn, _Args...>,
3003  __call_is_nothrow_<_Fn, _Args...>>::type
3004  { };
3005 
3006 #pragma GCC diagnostic push
3007 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
3008  struct __nonesuchbase {};
3009  struct __nonesuch : private __nonesuchbase {
3010  ~__nonesuch() = delete;
3011  __nonesuch(__nonesuch const&) = delete;
3012  void operator=(__nonesuch const&) = delete;
3013  };
3014 #pragma GCC diagnostic pop
3015  /// @endcond
3016 
3017 #if __cplusplus >= 201703L
3018 # define __cpp_lib_is_invocable 201703L
3019 
3020  /// std::invoke_result
3021  template<typename _Functor, typename... _ArgTypes>
3022  struct invoke_result
3023  : public __invoke_result<_Functor, _ArgTypes...>
3024  {
3025  static_assert(std::__is_complete_or_unbounded(__type_identity<_Functor>{}),
3026  "_Functor must be a complete class or an unbounded array");
3027  static_assert((std::__is_complete_or_unbounded(
3028  __type_identity<_ArgTypes>{}) && ...),
3029  "each argument type must be a complete class or an unbounded array");
3030  };
3031 
3032  /// std::invoke_result_t
3033  template<typename _Fn, typename... _Args>
3034  using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;
3035 
3036  /// std::is_invocable
3037  template<typename _Fn, typename... _ArgTypes>
3038  struct is_invocable
3039  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
3040  {
3041  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3042  "_Fn must be a complete class or an unbounded array");
3043  static_assert((std::__is_complete_or_unbounded(
3044  __type_identity<_ArgTypes>{}) && ...),
3045  "each argument type must be a complete class or an unbounded array");
3046  };
3047 
3048  /// std::is_invocable_r
3049  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3050  struct is_invocable_r
3051  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>::type
3052  {
3053  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3054  "_Fn must be a complete class or an unbounded array");
3055  static_assert((std::__is_complete_or_unbounded(
3056  __type_identity<_ArgTypes>{}) && ...),
3057  "each argument type must be a complete class or an unbounded array");
3058  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3059  "_Ret must be a complete class or an unbounded array");
3060  };
3061 
3062  /// std::is_nothrow_invocable
3063  template<typename _Fn, typename... _ArgTypes>
3064  struct is_nothrow_invocable
3065  : __and_<__is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>,
3066  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3067  {
3068  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3069  "_Fn must be a complete class or an unbounded array");
3070  static_assert((std::__is_complete_or_unbounded(
3071  __type_identity<_ArgTypes>{}) && ...),
3072  "each argument type must be a complete class or an unbounded array");
3073  };
3074 
3075  /// @cond undocumented
3076  template<typename _Result, typename _Ret, typename = void>
3077  struct __is_nt_invocable_impl : false_type { };
3078 
3079  template<typename _Result, typename _Ret>
3080  struct __is_nt_invocable_impl<_Result, _Ret,
3081  __void_t<typename _Result::type>>
3082  : __or_<is_void<_Ret>,
3083  __is_nothrow_convertible<typename _Result::type, _Ret>>
3084  { };
3085  /// @endcond
3086 
3087  /// std::is_nothrow_invocable_r
3088  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3089  struct is_nothrow_invocable_r
3090  : __and_<__is_nt_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>,
3091  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3092  {
3093  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3094  "_Fn must be a complete class or an unbounded array");
3095  static_assert((std::__is_complete_or_unbounded(
3096  __type_identity<_ArgTypes>{}) && ...),
3097  "each argument type must be a complete class or an unbounded array");
3098  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3099  "_Ret must be a complete class or an unbounded array");
3100  };
3101 #endif // C++17
3102 
3103 #if __cplusplus >= 201703L
3104 # define __cpp_lib_type_trait_variable_templates 201510L
3105  /**
3106  * @defgroup variable_templates Variable templates for type traits
3107  * @ingroup metaprogramming
3108  *
3109  * Each variable `is_xxx_v<T>` is a boolean constant with the same value
3110  * as the `value` member of the corresponding type trait `is_xxx<T>`.
3111  *
3112  * @since C++17 unless noted otherwise.
3113  */
3114 
3115  /**
3116  * @{
3117  * @ingroup variable_templates
3118  */
3119 template <typename _Tp>
3120  inline constexpr bool is_void_v = is_void<_Tp>::value;
3121 template <typename _Tp>
3122  inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
3123 template <typename _Tp>
3124  inline constexpr bool is_integral_v = is_integral<_Tp>::value;
3125 template <typename _Tp>
3126  inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
3127 template <typename _Tp>
3128  inline constexpr bool is_array_v = is_array<_Tp>::value;
3129 template <typename _Tp>
3130  inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
3131 template <typename _Tp>
3132  inline constexpr bool is_lvalue_reference_v =
3133  is_lvalue_reference<_Tp>::value;
3134 template <typename _Tp>
3135  inline constexpr bool is_rvalue_reference_v =
3136  is_rvalue_reference<_Tp>::value;
3137 template <typename _Tp>
3138  inline constexpr bool is_member_object_pointer_v =
3139  is_member_object_pointer<_Tp>::value;
3140 template <typename _Tp>
3141  inline constexpr bool is_member_function_pointer_v =
3142  is_member_function_pointer<_Tp>::value;
3143 template <typename _Tp>
3144  inline constexpr bool is_enum_v = is_enum<_Tp>::value;
3145 template <typename _Tp>
3146  inline constexpr bool is_union_v = is_union<_Tp>::value;
3147 template <typename _Tp>
3148  inline constexpr bool is_class_v = is_class<_Tp>::value;
3149 template <typename _Tp>
3150  inline constexpr bool is_function_v = is_function<_Tp>::value;
3151 template <typename _Tp>
3152  inline constexpr bool is_reference_v = is_reference<_Tp>::value;
3153 template <typename _Tp>
3154  inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
3155 template <typename _Tp>
3156  inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
3157 template <typename _Tp>
3158  inline constexpr bool is_object_v = is_object<_Tp>::value;
3159 template <typename _Tp>
3160  inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
3161 template <typename _Tp>
3162  inline constexpr bool is_compound_v = is_compound<_Tp>::value;
3163 template <typename _Tp>
3164  inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
3165 template <typename _Tp>
3166  inline constexpr bool is_const_v = is_const<_Tp>::value;
3167 template <typename _Tp>
3168  inline constexpr bool is_volatile_v = is_volatile<_Tp>::value;
3169 template <typename _Tp>
3170  inline constexpr bool is_trivial_v = is_trivial<_Tp>::value;
3171 template <typename _Tp>
3172  inline constexpr bool is_trivially_copyable_v =
3173  is_trivially_copyable<_Tp>::value;
3174 template <typename _Tp>
3175  inline constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
3176 #pragma GCC diagnostic push
3177 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
3178 template <typename _Tp>
3179  _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
3180  inline constexpr bool is_pod_v = is_pod<_Tp>::value;
3181 template <typename _Tp>
3182  _GLIBCXX17_DEPRECATED
3183  inline constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
3184 #pragma GCC diagnostic pop
3185  template <typename _Tp>
3186  inline constexpr bool is_empty_v = is_empty<_Tp>::value;
3187 template <typename _Tp>
3188  inline constexpr bool is_polymorphic_v = is_polymorphic<_Tp>::value;
3189 template <typename _Tp>
3190  inline constexpr bool is_abstract_v = is_abstract<_Tp>::value;
3191 template <typename _Tp>
3192  inline constexpr bool is_final_v = is_final<_Tp>::value;
3193 template <typename _Tp>
3194  inline constexpr bool is_signed_v = is_signed<_Tp>::value;
3195 template <typename _Tp>
3196  inline constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
3197 template <typename _Tp, typename... _Args>
3198  inline constexpr bool is_constructible_v =
3199  is_constructible<_Tp, _Args...>::value;
3200 template <typename _Tp>
3201  inline constexpr bool is_default_constructible_v =
3202  is_default_constructible<_Tp>::value;
3203 template <typename _Tp>
3204  inline constexpr bool is_copy_constructible_v =
3205  is_copy_constructible<_Tp>::value;
3206 template <typename _Tp>
3207  inline constexpr bool is_move_constructible_v =
3208  is_move_constructible<_Tp>::value;
3209 template <typename _Tp, typename _Up>
3210  inline constexpr bool is_assignable_v = is_assignable<_Tp, _Up>::value;
3211 template <typename _Tp>
3212  inline constexpr bool is_copy_assignable_v = is_copy_assignable<_Tp>::value;
3213 template <typename _Tp>
3214  inline constexpr bool is_move_assignable_v = is_move_assignable<_Tp>::value;
3215 template <typename _Tp>
3216  inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
3217 template <typename _Tp, typename... _Args>
3218  inline constexpr bool is_trivially_constructible_v =
3219  is_trivially_constructible<_Tp, _Args...>::value;
3220 template <typename _Tp>
3221  inline constexpr bool is_trivially_default_constructible_v =
3222  is_trivially_default_constructible<_Tp>::value;
3223 template <typename _Tp>
3224  inline constexpr bool is_trivially_copy_constructible_v =
3225  is_trivially_copy_constructible<_Tp>::value;
3226 template <typename _Tp>
3227  inline constexpr bool is_trivially_move_constructible_v =
3228  is_trivially_move_constructible<_Tp>::value;
3229 template <typename _Tp, typename _Up>
3230  inline constexpr bool is_trivially_assignable_v =
3231  is_trivially_assignable<_Tp, _Up>::value;
3232 template <typename _Tp>
3233  inline constexpr bool is_trivially_copy_assignable_v =
3234  is_trivially_copy_assignable<_Tp>::value;
3235 template <typename _Tp>
3236  inline constexpr bool is_trivially_move_assignable_v =
3237  is_trivially_move_assignable<_Tp>::value;
3238 template <typename _Tp>
3239  inline constexpr bool is_trivially_destructible_v =
3240  is_trivially_destructible<_Tp>::value;
3241 template <typename _Tp, typename... _Args>
3242  inline constexpr bool is_nothrow_constructible_v =
3243  is_nothrow_constructible<_Tp, _Args...>::value;
3244 template <typename _Tp>
3245  inline constexpr bool is_nothrow_default_constructible_v =
3246  is_nothrow_default_constructible<_Tp>::value;
3247 template <typename _Tp>
3248  inline constexpr bool is_nothrow_copy_constructible_v =
3249  is_nothrow_copy_constructible<_Tp>::value;
3250 template <typename _Tp>
3251  inline constexpr bool is_nothrow_move_constructible_v =
3252  is_nothrow_move_constructible<_Tp>::value;
3253 template <typename _Tp, typename _Up>
3254  inline constexpr bool is_nothrow_assignable_v =
3255  is_nothrow_assignable<_Tp, _Up>::value;
3256 template <typename _Tp>
3257  inline constexpr bool is_nothrow_copy_assignable_v =
3258  is_nothrow_copy_assignable<_Tp>::value;
3259 template <typename _Tp>
3260  inline constexpr bool is_nothrow_move_assignable_v =
3261  is_nothrow_move_assignable<_Tp>::value;
3262 template <typename _Tp>
3263  inline constexpr bool is_nothrow_destructible_v =
3264  is_nothrow_destructible<_Tp>::value;
3265 template <typename _Tp>
3266  inline constexpr bool has_virtual_destructor_v =
3267  has_virtual_destructor<_Tp>::value;
3268 template <typename _Tp>
3269  inline constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
3270 template <typename _Tp>
3271  inline constexpr size_t rank_v = rank<_Tp>::value;
3272 template <typename _Tp, unsigned _Idx = 0>
3273  inline constexpr size_t extent_v = extent<_Tp, _Idx>::value;
3274 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
3275 template <typename _Tp, typename _Up>
3276  inline constexpr bool is_same_v = __is_same(_Tp, _Up);
3277 #else
3278 template <typename _Tp, typename _Up>
3279  inline constexpr bool is_same_v = std::is_same<_Tp, _Up>::value;
3280 #endif
3281 template <typename _Base, typename _Derived>
3282  inline constexpr bool is_base_of_v = is_base_of<_Base, _Derived>::value;
3283 template <typename _From, typename _To>
3284  inline constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
3285 template<typename _Fn, typename... _Args>
3286  inline constexpr bool is_invocable_v = is_invocable<_Fn, _Args...>::value;
3287 template<typename _Fn, typename... _Args>
3288  inline constexpr bool is_nothrow_invocable_v
3289  = is_nothrow_invocable<_Fn, _Args...>::value;
3290 template<typename _Ret, typename _Fn, typename... _Args>
3291  inline constexpr bool is_invocable_r_v
3292  = is_invocable_r<_Ret, _Fn, _Args...>::value;
3293 template<typename _Ret, typename _Fn, typename... _Args>
3294  inline constexpr bool is_nothrow_invocable_r_v
3295  = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;
3296 /// @}
3297 
3298 #ifdef _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP
3299 # define __cpp_lib_has_unique_object_representations 201606L
3300  /// has_unique_object_representations
3301  /// @since C++17
3302  template<typename _Tp>
3303  struct has_unique_object_representations
3304  : bool_constant<__has_unique_object_representations(
3305  remove_cv_t<remove_all_extents_t<_Tp>>
3306  )>
3307  {
3308  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
3309  "template argument must be a complete class or an unbounded array");
3310  };
3311 
3312  /// @ingroup variable_templates
3313  template<typename _Tp>
3314  inline constexpr bool has_unique_object_representations_v
3315  = has_unique_object_representations<_Tp>::value;
3316 #endif
3317 
3318 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE
3319 # define __cpp_lib_is_aggregate 201703L
3320  /// is_aggregate
3321  /// @since C++17
3322  template<typename _Tp>
3323  struct is_aggregate
3324  : bool_constant<__is_aggregate(remove_cv_t<_Tp>)>
3325  { };
3326 
3327  /// @ingroup variable_templates
3328  template<typename _Tp>
3329  inline constexpr bool is_aggregate_v = is_aggregate<_Tp>::value;
3330 #endif
3331 #endif // C++17
3332 
3333 #if __cplusplus >= 202002L
3334 
3335  /** * Remove references and cv-qualifiers.
3336  * @since C++20
3337  * @{
3338  */
3339 #define __cpp_lib_remove_cvref 201711L
3340 
3341  template<typename _Tp>
3342  struct remove_cvref
3343  : remove_cv<_Tp>
3344  { };
3345 
3346  template<typename _Tp>
3347  struct remove_cvref<_Tp&>
3348  : remove_cv<_Tp>
3349  { };
3350 
3351  template<typename _Tp>
3352  struct remove_cvref<_Tp&&>
3353  : remove_cv<_Tp>
3354  { };
3355 
3356  template<typename _Tp>
3357  using remove_cvref_t = typename remove_cvref<_Tp>::type;
3358  /// @}
3359 
3360  /** * Identity metafunction.
3361  * @since C++20
3362  * @{
3363  */
3364 #define __cpp_lib_type_identity 201806L
3365  template<typename _Tp>
3366  struct type_identity { using type = _Tp; };
3367 
3368  template<typename _Tp>
3369  using type_identity_t = typename type_identity<_Tp>::type;
3370  /// @}
3371 
3372 #define __cpp_lib_unwrap_ref 201811L
3373 
3374  /** Unwrap a reference_wrapper
3375  * @since C++20
3376  * @{
3377  */
3378  template<typename _Tp>
3379  struct unwrap_reference { using type = _Tp; };
3380 
3381  template<typename _Tp>
3382  struct unwrap_reference<reference_wrapper<_Tp>> { using type = _Tp&; };
3383 
3384  template<typename _Tp>
3385  using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
3386  /// @}
3387 
3388  /** Decay type and if it's a reference_wrapper, unwrap it
3389  * @since C++20
3390  * @{
3391  */
3392  template<typename _Tp>
3393  struct unwrap_ref_decay { using type = unwrap_reference_t<decay_t<_Tp>>; };
3394 
3395  template<typename _Tp>
3396  using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
3397  /// @}
3398 
3399 #define __cpp_lib_bounded_array_traits 201902L
3400 
3401  /// True for a type that is an array of known bound.
3402  /// @since C++20
3403  template<typename _Tp>
3404  struct is_bounded_array
3405  : public __is_array_known_bounds<_Tp>
3406  { };
3407 
3408  /// True for a type that is an array of unknown bound.
3409  /// @since C++20
3410  template<typename _Tp>
3411  struct is_unbounded_array
3412  : public __is_array_unknown_bounds<_Tp>
3413  { };
3414 
3415  /// @ingroup variable_templates
3416  /// @since C++20
3417  template<typename _Tp>
3418  inline constexpr bool is_bounded_array_v
3419  = is_bounded_array<_Tp>::value;
3420 
3421  /// @ingroup variable_templates
3422  /// @since C++20
3423  template<typename _Tp>
3424  inline constexpr bool is_unbounded_array_v
3425  = is_unbounded_array<_Tp>::value;
3426 
3427 #if __has_builtin(__is_layout_compatible)
3428 
3429  /// @since C++20
3430  template<typename _Tp, typename _Up>
3431  struct is_layout_compatible
3432  : bool_constant<__is_layout_compatible(_Tp, _Up)>
3433  { };
3434 
3435  /// @ingroup variable_templates
3436  /// @since C++20
3437  template<typename _Tp, typename _Up>
3438  constexpr bool is_layout_compatible_v
3439  = __is_layout_compatible(_Tp, _Up);
3440 
3441 #if __has_builtin(__builtin_is_corresponding_member)
3442 #define __cpp_lib_is_layout_compatible 201907L
3443 
3444  /// @since C++20
3445  template<typename _S1, typename _S2, typename _M1, typename _M2>
3446  constexpr bool
3447  is_corresponding_member(_M1 _S1::*__m1, _M2 _S2::*__m2) noexcept
3448  { return __builtin_is_corresponding_member(__m1, __m2); }
3449 #endif
3450 #endif
3451 
3452 #if __has_builtin(__is_pointer_interconvertible_base_of)
3453  /// True if `_Derived` is standard-layout and has a base class of type `_Base`
3454  /// @since C++20
3455  template<typename _Base, typename _Derived>
3456  struct is_pointer_interconvertible_base_of
3457  : bool_constant<__is_pointer_interconvertible_base_of(_Base, _Derived)>
3458  { };
3459 
3460  /// @ingroup variable_templates
3461  /// @since C++20
3462  template<typename _Base, typename _Derived>
3463  constexpr bool is_pointer_interconvertible_base_of_v
3464  = __is_pointer_interconvertible_base_of(_Base, _Derived);
3465 
3466 #if __has_builtin(__builtin_is_pointer_interconvertible_with_class)
3467 #define __cpp_lib_is_pointer_interconvertible 201907L
3468 
3469  /// True if `__mp` points to the first member of a standard-layout type
3470  /// @returns true if `s.*__mp` is pointer-interconvertible with `s`
3471  /// @since C++20
3472  template<typename _Tp, typename _Mem>
3473  constexpr bool
3474  is_pointer_interconvertible_with_class(_Mem _Tp::*__mp) noexcept
3475  { return __builtin_is_pointer_interconvertible_with_class(__mp); }
3476 #endif
3477 #endif
3478 
3479 #if __cplusplus > 202002L
3480 #define __cpp_lib_is_scoped_enum 202011L
3481 
3482  /// True if the type is a scoped enumeration type.
3483  /// @since C++23
3484 
3485  template<typename _Tp>
3486  struct is_scoped_enum
3487  : false_type
3488  { };
3489 
3490  template<typename _Tp>
3491  requires __is_enum(_Tp)
3492  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3493  struct is_scoped_enum<_Tp>
3494  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3495  { };
3496 
3497  // FIXME remove this partial specialization and use remove_cv_t<_Tp> above
3498  // when PR c++/99968 is fixed.
3499  template<typename _Tp>
3500  requires __is_enum(_Tp)
3501  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3502  struct is_scoped_enum<const _Tp>
3503  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3504  { };
3505 
3506  /// @ingroup variable_templates
3507  /// @since C++23
3508  template<typename _Tp>
3509  inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
3510 
3511 #endif // C++23
3512 
3513 #if _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
3514 #define __cpp_lib_is_constant_evaluated 201811L
3515 
3516  /// Returns true only when called during constant evaluation.
3517  /// @since C++20
3518  constexpr inline bool
3519  is_constant_evaluated() noexcept
3520  {
3521 #if __cpp_if_consteval >= 202106L
3522  if consteval { return true; } else { return false; }
3523 #else
3524  return __builtin_is_constant_evaluated();
3525 #endif
3526  }
3527 #endif
3528 
3529  /// @cond undocumented
3530  template<typename _From, typename _To>
3531  using __copy_cv = typename __match_cv_qualifiers<_From, _To>::__type;
3532 
3533  template<typename _Xp, typename _Yp>
3534  using __cond_res
3535  = decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()());
3536 
3537  template<typename _Ap, typename _Bp, typename = void>
3538  struct __common_ref_impl
3539  { };
3540 
3541  // [meta.trans.other], COMMON-REF(A, B)
3542  template<typename _Ap, typename _Bp>
3543  using __common_ref = typename __common_ref_impl<_Ap, _Bp>::type;
3544 
3545  // COND-RES(COPYCV(X, Y) &, COPYCV(Y, X) &)
3546  template<typename _Xp, typename _Yp>
3547  using __condres_cvref
3548  = __cond_res<__copy_cv<_Xp, _Yp>&, __copy_cv<_Yp, _Xp>&>;
3549 
3550  // If A and B are both lvalue reference types, ...
3551  template<typename _Xp, typename _Yp>
3552  struct __common_ref_impl<_Xp&, _Yp&, __void_t<__condres_cvref<_Xp, _Yp>>>
3553  : enable_if<is_reference_v<__condres_cvref<_Xp, _Yp>>,
3554  __condres_cvref<_Xp, _Yp>>
3555  { };
3556 
3557  // let C be remove_reference_t<COMMON-REF(X&, Y&)>&&
3558  template<typename _Xp, typename _Yp>
3559  using __common_ref_C = remove_reference_t<__common_ref<_Xp&, _Yp&>>&&;
3560 
3561  // If A and B are both rvalue reference types, ...
3562  template<typename _Xp, typename _Yp>
3563  struct __common_ref_impl<_Xp&&, _Yp&&,
3564  _Require<is_convertible<_Xp&&, __common_ref_C<_Xp, _Yp>>,
3565  is_convertible<_Yp&&, __common_ref_C<_Xp, _Yp>>>>
3566  { using type = __common_ref_C<_Xp, _Yp>; };
3567 
3568  // let D be COMMON-REF(const X&, Y&)
3569  template<typename _Xp, typename _Yp>
3570  using __common_ref_D = __common_ref<const _Xp&, _Yp&>;
3571 
3572  // If A is an rvalue reference and B is an lvalue reference, ...
3573  template<typename _Xp, typename _Yp>
3574  struct __common_ref_impl<_Xp&&, _Yp&,
3575  _Require<is_convertible<_Xp&&, __common_ref_D<_Xp, _Yp>>>>
3576  { using type = __common_ref_D<_Xp, _Yp>; };
3577 
3578  // If A is an lvalue reference and B is an rvalue reference, ...
3579  template<typename _Xp, typename _Yp>
3580  struct __common_ref_impl<_Xp&, _Yp&&>
3581  : __common_ref_impl<_Yp&&, _Xp&>
3582  { };
3583  /// @endcond
3584 
3585  template<typename _Tp, typename _Up,
3586  template<typename> class _TQual, template<typename> class _UQual>
3587  struct basic_common_reference
3588  { };
3589 
3590  /// @cond undocumented
3591  template<typename _Tp>
3592  struct __xref
3593  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>; };
3594 
3595  template<typename _Tp>
3596  struct __xref<_Tp&>
3597  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&; };
3598 
3599  template<typename _Tp>
3600  struct __xref<_Tp&&>
3601  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&&; };
3602 
3603  template<typename _Tp1, typename _Tp2>
3604  using __basic_common_ref
3605  = typename basic_common_reference<remove_cvref_t<_Tp1>,
3606  remove_cvref_t<_Tp2>,
3607  __xref<_Tp1>::template __type,
3608  __xref<_Tp2>::template __type>::type;
3609  /// @endcond
3610 
3611  template<typename... _Tp>
3612  struct common_reference;
3613 
3614  template<typename... _Tp>
3615  using common_reference_t = typename common_reference<_Tp...>::type;
3616 
3617  // If sizeof...(T) is zero, there shall be no member type.
3618  template<>
3619  struct common_reference<>
3620  { };
3621 
3622  // If sizeof...(T) is one ...
3623  template<typename _Tp0>
3624  struct common_reference<_Tp0>
3625  { using type = _Tp0; };
3626 
3627  /// @cond undocumented
3628  template<typename _Tp1, typename _Tp2, int _Bullet = 1, typename = void>
3629  struct __common_reference_impl
3630  : __common_reference_impl<_Tp1, _Tp2, _Bullet + 1>
3631  { };
3632 
3633  // If sizeof...(T) is two ...
3634  template<typename _Tp1, typename _Tp2>
3635  struct common_reference<_Tp1, _Tp2>
3636  : __common_reference_impl<_Tp1, _Tp2>
3637  { };
3638 
3639  // If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, ...
3640  template<typename _Tp1, typename _Tp2>
3641  struct __common_reference_impl<_Tp1&, _Tp2&, 1,
3642  void_t<__common_ref<_Tp1&, _Tp2&>>>
3643  { using type = __common_ref<_Tp1&, _Tp2&>; };
3644 
3645  template<typename _Tp1, typename _Tp2>
3646  struct __common_reference_impl<_Tp1&&, _Tp2&&, 1,
3647  void_t<__common_ref<_Tp1&&, _Tp2&&>>>
3648  { using type = __common_ref<_Tp1&&, _Tp2&&>; };
3649 
3650  template<typename _Tp1, typename _Tp2>
3651  struct __common_reference_impl<_Tp1&, _Tp2&&, 1,
3652  void_t<__common_ref<_Tp1&, _Tp2&&>>>
3653  { using type = __common_ref<_Tp1&, _Tp2&&>; };
3654 
3655  template<typename _Tp1, typename _Tp2>
3656  struct __common_reference_impl<_Tp1&&, _Tp2&, 1,
3657  void_t<__common_ref<_Tp1&&, _Tp2&>>>
3658  { using type = __common_ref<_Tp1&&, _Tp2&>; };
3659 
3660  // Otherwise, if basic_common_reference<...>::type is well-formed, ...
3661  template<typename _Tp1, typename _Tp2>
3662  struct __common_reference_impl<_Tp1, _Tp2, 2,
3663  void_t<__basic_common_ref<_Tp1, _Tp2>>>
3664  { using type = __basic_common_ref<_Tp1, _Tp2>; };
3665 
3666  // Otherwise, if COND-RES(T1, T2) is well-formed, ...
3667  template<typename _Tp1, typename _Tp2>
3668  struct __common_reference_impl<_Tp1, _Tp2, 3,
3669  void_t<__cond_res<_Tp1, _Tp2>>>
3670  { using type = __cond_res<_Tp1, _Tp2>; };
3671 
3672  // Otherwise, if common_type_t<T1, T2> is well-formed, ...
3673  template<typename _Tp1, typename _Tp2>
3674  struct __common_reference_impl<_Tp1, _Tp2, 4,
3675  void_t<common_type_t<_Tp1, _Tp2>>>
3676  { using type = common_type_t<_Tp1, _Tp2>; };
3677 
3678  // Otherwise, there shall be no member type.
3679  template<typename _Tp1, typename _Tp2>
3680  struct __common_reference_impl<_Tp1, _Tp2, 5, void>
3681  { };
3682 
3683  // Otherwise, if sizeof...(T) is greater than two, ...
3684  template<typename _Tp1, typename _Tp2, typename... _Rest>
3685  struct common_reference<_Tp1, _Tp2, _Rest...>
3686  : __common_type_fold<common_reference<_Tp1, _Tp2>,
3687  __common_type_pack<_Rest...>>
3688  { };
3689 
3690  // Reuse __common_type_fold for common_reference<T1, T2, Rest...>
3691  template<typename _Tp1, typename _Tp2, typename... _Rest>
3692  struct __common_type_fold<common_reference<_Tp1, _Tp2>,
3693  __common_type_pack<_Rest...>,
3694  void_t<common_reference_t<_Tp1, _Tp2>>>
3695  : public common_reference<common_reference_t<_Tp1, _Tp2>, _Rest...>
3696  { };
3697  /// @endcond
3698 
3699 #endif // C++2a
3700 
3701  /// @} group metaprogramming
3702 
3703 _GLIBCXX_END_NAMESPACE_VERSION
3704 } // namespace std
3705 
3706 #endif // C++11
3707 
3708 #endif // _GLIBCXX_TYPE_TRAITS