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