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1 // -*- C++ -*- operator<=> three-way comparison support.
2 
3 // Copyright (C) 2019-2020 Free Software Foundation, Inc.
4 //
5 // This file is part of GCC.
6 //
7 // GCC is free software; you can redistribute it and/or modify
8 // it under the terms of the GNU General Public License as published by
9 // the Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 //
12 // GCC is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 //
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /** @file compare
27  * This is a Standard C++ Library header.
28  */
29 
30 #ifndef _COMPARE
31 #define _COMPARE
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus > 201703L && __cpp_impl_three_way_comparison >= 201907L
36 
37 #pragma GCC visibility push(default)
38 
39 #include <concepts>
40 
41 #if __cpp_lib_concepts
42 # define __cpp_lib_three_way_comparison 201711L
43 #endif
44 
45 namespace std
46 {
47  // [cmp.categories], comparison category types
48 
49  namespace __cmp_cat
50  {
51  using type = signed char;
52 
53  enum class _Ord : type { equivalent = 0, less = -1, greater = 1 };
54 
55  enum class _Ncmp : type { _Unordered = 2 };
56 
57  struct __unspec
58  {
59  constexpr __unspec(__unspec*) { }
60  };
61  }
62 
63  class partial_ordering
64  {
65  // less=0xff, equiv=0x00, greater=0x01, unordered=0x02
66  __cmp_cat::type _M_value;
67 
68  constexpr explicit
69  partial_ordering(__cmp_cat::_Ord __v) noexcept
70  : _M_value(__cmp_cat::type(__v))
71  { }
72 
73  constexpr explicit
74  partial_ordering(__cmp_cat::_Ncmp __v) noexcept
75  : _M_value(__cmp_cat::type(__v))
76  { }
77 
78  friend class weak_ordering;
79  friend class strong_ordering;
80 
81  public:
82  // valid values
83  static const partial_ordering less;
84  static const partial_ordering equivalent;
85  static const partial_ordering greater;
86  static const partial_ordering unordered;
87 
88  // comparisons
89  friend constexpr bool
90  operator==(partial_ordering __v, __cmp_cat::__unspec) noexcept
91  { return __v._M_value == 0; }
92 
93  friend constexpr bool
94  operator==(partial_ordering, partial_ordering) noexcept = default;
95 
96  friend constexpr bool
97  operator< (partial_ordering __v, __cmp_cat::__unspec) noexcept
98  { return __v._M_value == -1; }
99 
100  friend constexpr bool
101  operator> (partial_ordering __v, __cmp_cat::__unspec) noexcept
102  { return __v._M_value == 1; }
103 
104  friend constexpr bool
105  operator<=(partial_ordering __v, __cmp_cat::__unspec) noexcept
106  { return __v._M_value <= 0; }
107 
108  friend constexpr bool
109  operator>=(partial_ordering __v, __cmp_cat::__unspec) noexcept
110  { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; }
111 
112  friend constexpr bool
113  operator< (__cmp_cat::__unspec, partial_ordering __v) noexcept
114  { return __v._M_value == 1; }
115 
116  friend constexpr bool
117  operator> (__cmp_cat::__unspec, partial_ordering __v) noexcept
118  { return __v._M_value == -1; }
119 
120  friend constexpr bool
121  operator<=(__cmp_cat::__unspec, partial_ordering __v) noexcept
122  { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; }
123 
124  friend constexpr bool
125  operator>=(__cmp_cat::__unspec, partial_ordering __v) noexcept
126  { return 0 >= __v._M_value; }
127 
128  friend constexpr partial_ordering
129  operator<=>(partial_ordering __v, __cmp_cat::__unspec) noexcept
130  { return __v; }
131 
132  friend constexpr partial_ordering
133  operator<=>(__cmp_cat::__unspec, partial_ordering __v) noexcept
134  {
135  if (__v._M_value & 1)
136  return partial_ordering(__cmp_cat::_Ord(-__v._M_value));
137  else
138  return __v;
139  }
140  };
141 
142  // valid values' definitions
143  inline constexpr partial_ordering
144  partial_ordering::less(__cmp_cat::_Ord::less);
145 
146  inline constexpr partial_ordering
147  partial_ordering::equivalent(__cmp_cat::_Ord::equivalent);
148 
149  inline constexpr partial_ordering
150  partial_ordering::greater(__cmp_cat::_Ord::greater);
151 
152  inline constexpr partial_ordering
153  partial_ordering::unordered(__cmp_cat::_Ncmp::_Unordered);
154 
155  class weak_ordering
156  {
157  __cmp_cat::type _M_value;
158 
159  constexpr explicit
160  weak_ordering(__cmp_cat::_Ord __v) noexcept : _M_value(__cmp_cat::type(__v))
161  { }
162 
163  friend class strong_ordering;
164 
165  public:
166  // valid values
167  static const weak_ordering less;
168  static const weak_ordering equivalent;
169  static const weak_ordering greater;
170 
171  constexpr operator partial_ordering() const noexcept
172  { return partial_ordering(__cmp_cat::_Ord(_M_value)); }
173 
174  // comparisons
175  friend constexpr bool
176  operator==(weak_ordering __v, __cmp_cat::__unspec) noexcept
177  { return __v._M_value == 0; }
178 
179  friend constexpr bool
180  operator==(weak_ordering, weak_ordering) noexcept = default;
181 
182  friend constexpr bool
183  operator< (weak_ordering __v, __cmp_cat::__unspec) noexcept
184  { return __v._M_value < 0; }
185 
186  friend constexpr bool
187  operator> (weak_ordering __v, __cmp_cat::__unspec) noexcept
188  { return __v._M_value > 0; }
189 
190  friend constexpr bool
191  operator<=(weak_ordering __v, __cmp_cat::__unspec) noexcept
192  { return __v._M_value <= 0; }
193 
194  friend constexpr bool
195  operator>=(weak_ordering __v, __cmp_cat::__unspec) noexcept
196  { return __v._M_value >= 0; }
197 
198  friend constexpr bool
199  operator< (__cmp_cat::__unspec, weak_ordering __v) noexcept
200  { return 0 < __v._M_value; }
201 
202  friend constexpr bool
203  operator> (__cmp_cat::__unspec, weak_ordering __v) noexcept
204  { return 0 > __v._M_value; }
205 
206  friend constexpr bool
207  operator<=(__cmp_cat::__unspec, weak_ordering __v) noexcept
208  { return 0 <= __v._M_value; }
209 
210  friend constexpr bool
211  operator>=(__cmp_cat::__unspec, weak_ordering __v) noexcept
212  { return 0 >= __v._M_value; }
213 
214  friend constexpr weak_ordering
215  operator<=>(weak_ordering __v, __cmp_cat::__unspec) noexcept
216  { return __v; }
217 
218  friend constexpr weak_ordering
219  operator<=>(__cmp_cat::__unspec, weak_ordering __v) noexcept
220  { return weak_ordering(__cmp_cat::_Ord(-__v._M_value)); }
221  };
222 
223  // valid values' definitions
224  inline constexpr weak_ordering
225  weak_ordering::less(__cmp_cat::_Ord::less);
226 
227  inline constexpr weak_ordering
228  weak_ordering::equivalent(__cmp_cat::_Ord::equivalent);
229 
230  inline constexpr weak_ordering
231  weak_ordering::greater(__cmp_cat::_Ord::greater);
232 
233  class strong_ordering
234  {
235  __cmp_cat::type _M_value;
236 
237  constexpr explicit
238  strong_ordering(__cmp_cat::_Ord __v) noexcept
239  : _M_value(__cmp_cat::type(__v))
240  { }
241 
242  public:
243  // valid values
244  static const strong_ordering less;
245  static const strong_ordering equal;
246  static const strong_ordering equivalent;
247  static const strong_ordering greater;
248 
249  constexpr operator partial_ordering() const noexcept
250  { return partial_ordering(__cmp_cat::_Ord(_M_value)); }
251 
252  constexpr operator weak_ordering() const noexcept
253  { return weak_ordering(__cmp_cat::_Ord(_M_value)); }
254 
255  // comparisons
256  friend constexpr bool
257  operator==(strong_ordering __v, __cmp_cat::__unspec) noexcept
258  { return __v._M_value == 0; }
259 
260  friend constexpr bool
261  operator==(strong_ordering, strong_ordering) noexcept = default;
262 
263  friend constexpr bool
264  operator< (strong_ordering __v, __cmp_cat::__unspec) noexcept
265  { return __v._M_value < 0; }
266 
267  friend constexpr bool
268  operator> (strong_ordering __v, __cmp_cat::__unspec) noexcept
269  { return __v._M_value > 0; }
270 
271  friend constexpr bool
272  operator<=(strong_ordering __v, __cmp_cat::__unspec) noexcept
273  { return __v._M_value <= 0; }
274 
275  friend constexpr bool
276  operator>=(strong_ordering __v, __cmp_cat::__unspec) noexcept
277  { return __v._M_value >= 0; }
278 
279  friend constexpr bool
280  operator< (__cmp_cat::__unspec, strong_ordering __v) noexcept
281  { return 0 < __v._M_value; }
282 
283  friend constexpr bool
284  operator> (__cmp_cat::__unspec, strong_ordering __v) noexcept
285  { return 0 > __v._M_value; }
286 
287  friend constexpr bool
288  operator<=(__cmp_cat::__unspec, strong_ordering __v) noexcept
289  { return 0 <= __v._M_value; }
290 
291  friend constexpr bool
292  operator>=(__cmp_cat::__unspec, strong_ordering __v) noexcept
293  { return 0 >= __v._M_value; }
294 
295  friend constexpr strong_ordering
296  operator<=>(strong_ordering __v, __cmp_cat::__unspec) noexcept
297  { return __v; }
298 
299  friend constexpr strong_ordering
300  operator<=>(__cmp_cat::__unspec, strong_ordering __v) noexcept
301  { return strong_ordering(__cmp_cat::_Ord(-__v._M_value)); }
302  };
303 
304  // valid values' definitions
305  inline constexpr strong_ordering
306  strong_ordering::less(__cmp_cat::_Ord::less);
307 
308  inline constexpr strong_ordering
309  strong_ordering::equal(__cmp_cat::_Ord::equivalent);
310 
311  inline constexpr strong_ordering
312  strong_ordering::equivalent(__cmp_cat::_Ord::equivalent);
313 
314  inline constexpr strong_ordering
315  strong_ordering::greater(__cmp_cat::_Ord::greater);
316 
317 
318  // named comparison functions
319  constexpr bool
320  is_eq(partial_ordering __cmp) noexcept
321  { return __cmp == 0; }
322 
323  constexpr bool
324  is_neq(partial_ordering __cmp) noexcept
325  { return __cmp != 0; }
326 
327  constexpr bool
328  is_lt (partial_ordering __cmp) noexcept
329  { return __cmp < 0; }
330 
331  constexpr bool
332  is_lteq(partial_ordering __cmp) noexcept
333  { return __cmp <= 0; }
334 
335  constexpr bool
336  is_gt (partial_ordering __cmp) noexcept
337  { return __cmp > 0; }
338 
339  constexpr bool
340  is_gteq(partial_ordering __cmp) noexcept
341  { return __cmp >= 0; }
342 
343  namespace __detail
344  {
345  template<typename _Tp>
346  inline constexpr unsigned __cmp_cat_id = 1;
347  template<>
348  inline constexpr unsigned __cmp_cat_id<partial_ordering> = 2;
349  template<>
350  inline constexpr unsigned __cmp_cat_id<weak_ordering> = 4;
351  template<>
352  inline constexpr unsigned __cmp_cat_id<strong_ordering> = 8;
353 
354  template<typename... _Ts>
355  constexpr auto __common_cmp_cat()
356  {
357  constexpr unsigned __cats = (__cmp_cat_id<_Ts> | ...);
358  // If any Ti is not a comparison category type, U is void.
359  if constexpr (__cats & 1)
360  return;
361  // Otherwise, if at least one Ti is std::partial_ordering,
362  // U is std::partial_ordering.
363  else if constexpr (bool(__cats & __cmp_cat_id<partial_ordering>))
364  return partial_ordering::equivalent;
365  // Otherwise, if at least one Ti is std::weak_ordering,
366  // U is std::weak_ordering.
367  else if constexpr (bool(__cats & __cmp_cat_id<weak_ordering>))
368  return weak_ordering::equivalent;
369  // Otherwise, U is std::strong_ordering.
370  else
371  return strong_ordering::equivalent;
372  }
373  } // namespace __detail
374 
375  // [cmp.common], common comparison category type
376  template<typename... _Ts>
377  struct common_comparison_category
378  {
379  using type = decltype(__detail::__common_cmp_cat<_Ts...>());
380  };
381 
382  // Partial specializations for one and zero argument cases.
383 
384  template<typename _Tp>
385  struct common_comparison_category<_Tp>
386  { using type = void; };
387 
388  template<>
389  struct common_comparison_category<partial_ordering>
390  { using type = partial_ordering; };
391 
392  template<>
393  struct common_comparison_category<weak_ordering>
394  { using type = weak_ordering; };
395 
396  template<>
397  struct common_comparison_category<strong_ordering>
398  { using type = strong_ordering; };
399 
400  template<>
401  struct common_comparison_category<>
402  { using type = strong_ordering; };
403 
404  template<typename... _Ts>
405  using common_comparison_category_t
406  = typename common_comparison_category<_Ts...>::type;
407 
408 #if __cpp_lib_concepts
409  namespace __detail
410  {
411  template<typename _Tp, typename _Cat>
412  concept __compares_as
413  = same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>;
414 
415  template<typename _Tp, typename _Up>
416  concept __partially_ordered_with
417  = requires(const remove_reference_t<_Tp>& __t,
418  const remove_reference_t<_Up>& __u) {
419  { __t < __u } -> boolean;
420  { __t > __u } -> boolean;
421  { __t <= __u } -> boolean;
422  { __t >= __u } -> boolean;
423  { __u < __t } -> boolean;
424  { __u > __t } -> boolean;
425  { __u <= __t } -> boolean;
426  { __u >= __t } -> boolean;
427  };
428  } // namespace __detail
429 
430  // [cmp.concept], concept three_way_comparable
431  template<typename _Tp, typename _Cat = partial_ordering>
432  concept three_way_comparable
433  = __detail::__weakly_eq_cmp_with<_Tp, _Tp>
434  && (!convertible_to<_Cat, partial_ordering>
435  || __detail::__partially_ordered_with<_Tp, _Tp>)
436  && requires(const remove_reference_t<_Tp>& __a,
437  const remove_reference_t<_Tp>& __b) {
438  { __a <=> __b } -> __detail::__compares_as<_Cat>;
439  };
440 
441  template<typename _Tp, typename _Up, typename _Cat = partial_ordering>
442  concept three_way_comparable_with
443  = __detail::__weakly_eq_cmp_with<_Tp, _Up>
444  && (!convertible_to<_Cat, partial_ordering>
445  || __detail::__partially_ordered_with<_Tp, _Up>)
446  && three_way_comparable<_Tp, _Cat>
447  && three_way_comparable<_Up, _Cat>
448  && common_reference_with<const remove_reference_t<_Tp>&,
449  const remove_reference_t<_Up>&>
450  && three_way_comparable<
451  common_reference_t<const remove_reference_t<_Tp>&,
452  const remove_reference_t<_Up>&>, _Cat>
453  && requires(const remove_reference_t<_Tp>& __t,
454  const remove_reference_t<_Up>& __u) {
455  { __t <=> __u } -> __detail::__compares_as<_Cat>;
456  { __u <=> __t } -> __detail::__compares_as<_Cat>;
457  };
458 
459  namespace __detail
460  {
461  template<typename _Tp, typename _Up>
462  using __cmp3way_res_t
463  = decltype(std::declval<_Tp>() <=> std::declval<_Up>());
464 
465  // Implementation of std::compare_three_way_result.
466  // It is undefined for a program to add specializations of
467  // std::compare_three_way_result, so the std::compare_three_way_result_t
468  // alias ignores std::compare_three_way_result and uses
469  // __detail::__cmp3way_res_impl directly instead.
470  template<typename _Tp, typename _Up>
471  struct __cmp3way_res_impl
472  { };
473 
474  template<typename _Tp, typename _Up>
475  requires requires { typename __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>; }
476  struct __cmp3way_res_impl<_Tp, _Up>
477  {
478  using type = __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>;
479  };
480  } // namespace __detail
481 
482  /// [cmp.result], result of three-way comparison
483  template<typename _Tp, typename _Up = _Tp>
484  struct compare_three_way_result
485  : __detail::__cmp3way_res_impl<_Tp, _Up>
486  { };
487 
488  /// [cmp.result], result of three-way comparison
489  template<typename _Tp, typename _Up = _Tp>
490  using compare_three_way_result_t
491  = typename __detail::__cmp3way_res_impl<_Tp, _Up>::type;
492 
493  namespace __detail
494  {
495  // BUILTIN-PTR-THREE-WAY(T, U)
496  template<typename _Tp, typename _Up>
497  concept __3way_builtin_ptr_cmp
498  = three_way_comparable_with<_Tp, _Up>
499  && convertible_to<_Tp, const volatile void*>
500  && convertible_to<_Up, const volatile void*>
501  && ! requires(_Tp&& __t, _Up&& __u)
502  { operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
503  && ! requires(_Tp&& __t, _Up&& __u)
504  { static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); };
505  } // namespace __detail
506 
507  // [cmp.object], typename compare_three_way
508  struct compare_three_way
509  {
510  template<typename _Tp, typename _Up>
511  requires three_way_comparable_with<_Tp, _Up>
512  constexpr auto
513  operator()(_Tp&& __t, _Up&& __u) const noexcept
514  {
515  if constexpr (__detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
516  {
517  auto __pt = static_cast<const volatile void*>(__t);
518  auto __pu = static_cast<const volatile void*>(__u);
519  if (__builtin_is_constant_evaluated())
520  return __pt <=> __pu;
521  auto __it = reinterpret_cast<__UINTPTR_TYPE__>(__pt);
522  auto __iu = reinterpret_cast<__UINTPTR_TYPE__>(__pu);
523  return __it <=> __iu;
524  }
525  else
526  return static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u);
527  }
528 
529  using is_transparent = void;
530  };
531 
532  namespace __cmp_cust
533  {
534  template<floating_point _Tp>
535  constexpr weak_ordering
536  __fp_weak_ordering(_Tp __e, _Tp __f)
537  {
538  // Returns an integer with the same sign as the argument, and magnitude
539  // indicating the classification: zero=1 subnorm=2 norm=3 inf=4 nan=5
540  auto __cat = [](_Tp __fp) -> int {
541  const int __sign = __builtin_signbit(__fp) ? -1 : 1;
542  if (__builtin_isnormal(__fp))
543  return (__fp == 0 ? 1 : 3) * __sign;
544  if (__builtin_isnan(__fp))
545  return 5 * __sign;
546  if (int __inf = __builtin_isinf_sign(__fp))
547  return 4 * __inf;
548  return 2 * __sign;
549  };
550 
551  auto __po = __e <=> __f;
552  if (is_lt(__po))
553  return weak_ordering::less;
554  else if (is_gt(__po))
555  return weak_ordering::greater;
556  else if (__po == partial_ordering::equivalent)
557  return weak_ordering::equivalent;
558  else // unordered, at least one argument is NaN
559  {
560  // return -1 for negative nan, +1 for positive nan, 0 otherwise.
561  auto __isnan_sign = [](_Tp __fp) -> int {
562  return __builtin_isnan(__fp)
563  ? __builtin_signbit(__fp) ? -1 : 1
564  : 0;
565  };
566  auto __ord = __isnan_sign(__e) <=> __isnan_sign(__f);
567  if (is_eq(__ord))
568  return weak_ordering::equivalent;
569  else if (is_lt(__ord))
570  return weak_ordering::less;
571  else
572  return weak_ordering::greater;
573  }
574  }
575 
576  template<typename _Tp, typename _Up>
577  concept __adl_strong = requires(_Tp&& __t, _Up&& __u)
578  {
579  strong_ordering(strong_order(static_cast<_Tp&&>(__t),
580  static_cast<_Up&&>(__u)));
581  };
582 
583  template<typename _Tp, typename _Up>
584  concept __adl_weak = requires(_Tp&& __t, _Up&& __u)
585  {
586  weak_ordering(weak_order(static_cast<_Tp&&>(__t),
587  static_cast<_Up&&>(__u)));
588  };
589 
590  template<typename _Tp, typename _Up>
591  concept __adl_partial = requires(_Tp&& __t, _Up&& __u)
592  {
593  partial_ordering(partial_order(static_cast<_Tp&&>(__t),
594  static_cast<_Up&&>(__u)));
595  };
596 
597  template<typename _Ord, typename _Tp, typename _Up>
598  concept __op_cmp = requires(_Tp&& __t, _Up&& __u)
599  {
600  _Ord(static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u));
601  };
602 
603  template<typename _Tp, typename _Up>
604  concept __strongly_ordered
605  = __adl_strong<_Tp, _Up>
606  // FIXME: || floating_point<remove_reference_t<_Tp>>
607  || __op_cmp<strong_ordering, _Tp, _Up>;
608 
609  class _Strong_order
610  {
611  template<typename _Tp, typename _Up>
612  static constexpr bool
613  _S_noexcept()
614  {
615  if constexpr (floating_point<decay_t<_Tp>>)
616  return true;
617  else if constexpr (__adl_strong<_Tp, _Up>)
618  return noexcept(strong_ordering(strong_order(std::declval<_Tp>(),
619  std::declval<_Up>())));
620  else if constexpr (__op_cmp<strong_ordering, _Tp, _Up>)
621  return noexcept(std::declval<_Tp>() <=> std::declval<_Up>());
622  }
623 
624  friend class _Weak_order;
625  friend class _Strong_fallback;
626 
627  public:
628  template<typename _Tp, typename _Up>
629  requires __strongly_ordered<_Tp, _Up>
630  constexpr strong_ordering
631  operator()(_Tp&& __e, _Up&& __f) const
632  noexcept(_S_noexcept<_Tp, _Up>())
633  {
634  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
635 
636  /* FIXME:
637  if constexpr (floating_point<decay_t<_Tp>>)
638  return __cmp_cust::__fp_strong_order(__e, __f);
639  else */ if constexpr (__adl_strong<_Tp, _Up>)
640  return strong_ordering(strong_order(static_cast<_Tp&&>(__e),
641  static_cast<_Up&&>(__f)));
642  else if constexpr (__op_cmp<strong_ordering, _Tp, _Up>)
643  return static_cast<_Tp&&>(__e) <=> static_cast<_Up&&>(__f);
644  }
645  };
646 
647  template<typename _Tp, typename _Up>
648  concept __weakly_ordered
649  = floating_point<remove_reference_t<_Tp>>
650  || __adl_weak<_Tp, _Up>
651  || __op_cmp<weak_ordering, _Tp, _Up>
652  || __strongly_ordered<_Tp, _Up>;
653 
654  class _Weak_order
655  {
656  template<typename _Tp, typename _Up>
657  static constexpr bool
658  _S_noexcept()
659  {
660  if constexpr (floating_point<decay_t<_Tp>>)
661  return true;
662  else if constexpr (__adl_weak<_Tp, _Up>)
663  return noexcept(weak_ordering(weak_order(std::declval<_Tp>(),
664  std::declval<_Up>())));
665  else if constexpr (__op_cmp<weak_ordering, _Tp, _Up>)
666  return noexcept(std::declval<_Tp>() <=> std::declval<_Up>());
667  else if constexpr (__strongly_ordered<_Tp, _Up>)
668  return _Strong_order::_S_noexcept<_Tp, _Up>();
669  }
670 
671  friend class _Partial_order;
672  friend class _Weak_fallback;
673 
674  public:
675  template<typename _Tp, typename _Up>
676  requires __weakly_ordered<_Tp, _Up>
677  constexpr weak_ordering
678  operator()(_Tp&& __e, _Up&& __f) const
679  noexcept(_S_noexcept<_Tp, _Up>())
680  {
681  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
682 
683  if constexpr (floating_point<decay_t<_Tp>>)
684  return __cmp_cust::__fp_weak_ordering(__e, __f);
685  else if constexpr (__adl_weak<_Tp, _Up>)
686  return weak_ordering(weak_order(static_cast<_Tp&&>(__e),
687  static_cast<_Up&&>(__f)));
688  else if constexpr (__op_cmp<weak_ordering, _Tp, _Up>)
689  return static_cast<_Tp&&>(__e) <=> static_cast<_Up&&>(__f);
690  else if constexpr (__strongly_ordered<_Tp, _Up>)
691  return _Strong_order{}(static_cast<_Tp&&>(__e),
692  static_cast<_Up&&>(__f));
693  }
694  };
695 
696  template<typename _Tp, typename _Up>
697  concept __partially_ordered
698  = __adl_partial<_Tp, _Up>
699  || __op_cmp<partial_ordering, _Tp, _Up>
700  || __weakly_ordered<_Tp, _Up>;
701 
702  class _Partial_order
703  {
704  template<typename _Tp, typename _Up>
705  static constexpr bool
706  _S_noexcept()
707  {
708  if constexpr (__adl_partial<_Tp, _Up>)
709  return noexcept(partial_ordering(partial_order(std::declval<_Tp>(),
710  std::declval<_Up>())));
711  else if constexpr (__op_cmp<partial_ordering, _Tp, _Up>)
712  return noexcept(std::declval<_Tp>() <=> std::declval<_Up>());
713  else if constexpr (__weakly_ordered<_Tp, _Up>)
714  return _Weak_order::_S_noexcept<_Tp, _Up>();
715  }
716 
717  friend class _Partial_fallback;
718 
719  public:
720  template<typename _Tp, typename _Up>
721  requires __partially_ordered<_Tp, _Up>
722  constexpr partial_ordering
723  operator()(_Tp&& __e, _Up&& __f) const
724  noexcept(_S_noexcept<_Tp, _Up>())
725  {
726  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
727 
728  if constexpr (__adl_partial<_Tp, _Up>)
729  return partial_ordering(partial_order(static_cast<_Tp&&>(__e),
730  static_cast<_Up&&>(__f)));
731  else if constexpr (__op_cmp<partial_ordering, _Tp, _Up>)
732  return static_cast<_Tp&&>(__e) <=> static_cast<_Up&&>(__f);
733  else if constexpr (__weakly_ordered<_Tp, _Up>)
734  return _Weak_order{}(static_cast<_Tp&&>(__e),
735  static_cast<_Up&&>(__f));
736  }
737  };
738 
739  template<typename _Tp, typename _Up>
740  concept __op_eq_lt = requires(_Tp&& __t, _Up&& __u)
741  {
742  { static_cast<_Tp&&>(__t) == static_cast<_Up&&>(__u) }
743  -> convertible_to<bool>;
744  { static_cast<_Tp&&>(__t) < static_cast<_Up&&>(__u) }
745  -> convertible_to<bool>;
746  };
747 
748  class _Strong_fallback
749  {
750  template<typename _Tp, typename _Up>
751  static constexpr bool
752  _S_noexcept()
753  {
754  if constexpr (__strongly_ordered<_Tp, _Up>)
755  return _Strong_order::_S_noexcept<_Tp, _Up>();
756  else
757  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
758  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
759  }
760 
761  public:
762  template<typename _Tp, typename _Up>
763  requires __strongly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
764  constexpr decltype(auto)
765  operator()(_Tp&& __e, _Up&& __f) const
766  noexcept(_S_noexcept<_Tp, _Up>())
767  {
768  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
769 
770  if constexpr (__strongly_ordered<_Tp, _Up>)
771  return _Strong_order{}(static_cast<_Tp&&>(__e),
772  static_cast<_Up&&>(__f));
773  else if constexpr (__op_eq_lt<_Tp, _Up>)
774  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
775  ? strong_ordering::equal
776  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
777  ? strong_ordering::less
778  : strong_ordering::greater;
779  }
780  };
781 
782  class _Weak_fallback
783  {
784  template<typename _Tp, typename _Up>
785  static constexpr bool
786  _S_noexcept()
787  {
788  if constexpr (__weakly_ordered<_Tp, _Up>)
789  return _Weak_order::_S_noexcept<_Tp, _Up>();
790  else
791  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
792  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
793  }
794 
795  public:
796  template<typename _Tp, typename _Up>
797  requires __weakly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
798  constexpr decltype(auto)
799  operator()(_Tp&& __e, _Up&& __f) const
800  noexcept(_S_noexcept<_Tp, _Up>())
801  {
802  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
803 
804  if constexpr (__weakly_ordered<_Tp, _Up>)
805  return _Weak_order{}(static_cast<_Tp&&>(__e),
806  static_cast<_Up&&>(__f));
807  else if constexpr (__op_eq_lt<_Tp, _Up>)
808  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
809  ? weak_ordering::equivalent
810  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
811  ? weak_ordering::less
812  : weak_ordering::greater;
813  }
814  };
815 
816  class _Partial_fallback
817  {
818  template<typename _Tp, typename _Up>
819  static constexpr bool
820  _S_noexcept()
821  {
822  if constexpr (__partially_ordered<_Tp, _Up>)
823  return _Partial_order::_S_noexcept<_Tp, _Up>();
824  else
825  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
826  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
827  }
828 
829  public:
830  template<typename _Tp, typename _Up>
831  requires __partially_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
832  constexpr decltype(auto)
833  operator()(_Tp&& __e, _Up&& __f) const
834  noexcept(_S_noexcept<_Tp, _Up>())
835  {
836  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
837 
838  if constexpr (__partially_ordered<_Tp, _Up>)
839  return _Partial_order{}(static_cast<_Tp&&>(__e),
840  static_cast<_Up&&>(__f));
841  else if constexpr (__op_eq_lt<_Tp, _Up>)
842  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
843  ? partial_ordering::equivalent
844  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
845  ? partial_ordering::less
846  : static_cast<_Up&&>(__f) < static_cast<_Tp&&>(__e)
847  ? partial_ordering::greater
848  : partial_ordering::unordered;
849  }
850  };
851  } // namespace __cmp_cust
852 
853  // [cmp.alg], comparison algorithms
854  inline namespace __cmp_alg
855  {
856  inline constexpr __cmp_cust::_Strong_order strong_order{};
857 
858  inline constexpr __cmp_cust::_Weak_order weak_order{};
859 
860  inline constexpr __cmp_cust::_Partial_order partial_order{};
861 
862  inline constexpr __cmp_cust::_Strong_fallback
863  compare_strong_order_fallback{};
864 
865  inline constexpr __cmp_cust::_Weak_fallback
866  compare_weak_order_fallback{};
867 
868  inline constexpr __cmp_cust::_Partial_fallback
869  compare_partial_order_fallback{};
870  }
871 
872  namespace __detail
873  {
874  // [expos.only.func]
875  inline constexpr struct _Synth3way
876  {
877  template<typename _Tp, typename _Up>
878  constexpr auto
879  operator()(const _Tp& __t, const _Up& __u) const
880  requires requires
881  {
882  { __t < __u } -> convertible_to<bool>;
883  { __u < __t } -> convertible_to<bool>;
884  }
885  {
886  if constexpr (three_way_comparable_with<_Tp, _Up>)
887  return __t <=> __u;
888  else
889  {
890  if (__t < __u)
891  return weak_ordering::less;
892  else if (__u < __t)
893  return weak_ordering::greater;
894  else
895  return weak_ordering::equivalent;
896  }
897  }
898  } __synth3way = {};
899 
900  template<typename _Tp, typename _Up = _Tp>
901  using __synth3way_t
902  = decltype(__detail::__synth3way(std::declval<_Tp&>(),
903  std::declval<_Up&>()));
904  } // namespace __detail
905 #endif // concepts
906 } // namespace std
907 
908 #pragma GCC visibility pop
909 
910 #endif // C++20
911 
912 #endif // _COMPARE
std
ISO C++ entities toplevel namespace is std.
concepts