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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 201907L
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*) noexcept { }
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  } // namespace __detail
415 
416  // [cmp.concept], concept three_way_comparable
417  template<typename _Tp, typename _Cat = partial_ordering>
418  concept three_way_comparable
419  = __detail::__weakly_eq_cmp_with<_Tp, _Tp>
420  && __detail::__partially_ordered_with<_Tp, _Tp>
421  && requires(const remove_reference_t<_Tp>& __a,
422  const remove_reference_t<_Tp>& __b)
423  {
424  { __a <=> __b } -> __detail::__compares_as<_Cat>;
425  };
426 
427  template<typename _Tp, typename _Up, typename _Cat = partial_ordering>
428  concept three_way_comparable_with
429  = three_way_comparable<_Tp, _Cat>
430  && three_way_comparable<_Up, _Cat>
431  && common_reference_with<const remove_reference_t<_Tp>&,
432  const remove_reference_t<_Up>&>
433  && three_way_comparable<
434  common_reference_t<const remove_reference_t<_Tp>&,
435  const remove_reference_t<_Up>&>, _Cat>
436  && __detail::__weakly_eq_cmp_with<_Tp, _Up>
437  && __detail::__partially_ordered_with<_Tp, _Up>
438  && requires(const remove_reference_t<_Tp>& __t,
439  const remove_reference_t<_Up>& __u)
440  {
441  { __t <=> __u } -> __detail::__compares_as<_Cat>;
442  { __u <=> __t } -> __detail::__compares_as<_Cat>;
443  };
444 
445  namespace __detail
446  {
447  template<typename _Tp, typename _Up>
448  using __cmp3way_res_t
449  = decltype(std::declval<_Tp>() <=> std::declval<_Up>());
450 
451  // Implementation of std::compare_three_way_result.
452  // It is undefined for a program to add specializations of
453  // std::compare_three_way_result, so the std::compare_three_way_result_t
454  // alias ignores std::compare_three_way_result and uses
455  // __detail::__cmp3way_res_impl directly instead.
456  template<typename _Tp, typename _Up>
457  struct __cmp3way_res_impl
458  { };
459 
460  template<typename _Tp, typename _Up>
461  requires requires { typename __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>; }
462  struct __cmp3way_res_impl<_Tp, _Up>
463  {
464  using type = __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>;
465  };
466  } // namespace __detail
467 
468  /// [cmp.result], result of three-way comparison
469  template<typename _Tp, typename _Up = _Tp>
470  struct compare_three_way_result
471  : __detail::__cmp3way_res_impl<_Tp, _Up>
472  { };
473 
474  /// [cmp.result], result of three-way comparison
475  template<typename _Tp, typename _Up = _Tp>
476  using compare_three_way_result_t
477  = typename __detail::__cmp3way_res_impl<_Tp, _Up>::type;
478 
479  namespace __detail
480  {
481  // BUILTIN-PTR-THREE-WAY(T, U)
482  template<typename _Tp, typename _Up>
483  concept __3way_builtin_ptr_cmp
484  = requires(_Tp&& __t, _Up&& __u)
485  { static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u); }
486  && convertible_to<_Tp, const volatile void*>
487  && convertible_to<_Up, const volatile void*>
488  && ! requires(_Tp&& __t, _Up&& __u)
489  { operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
490  && ! requires(_Tp&& __t, _Up&& __u)
491  { static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); };
492  } // namespace __detail
493 
494  // [cmp.object], typename compare_three_way
495  struct compare_three_way
496  {
497  template<typename _Tp, typename _Up>
498  requires three_way_comparable_with<_Tp, _Up>
499  || __detail::__3way_builtin_ptr_cmp<_Tp, _Up>
500  constexpr auto
501  operator()(_Tp&& __t, _Up&& __u) const
502  noexcept(noexcept(std::declval<_Tp>() <=> std::declval<_Up>()))
503  {
504  if constexpr (__detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
505  {
506  auto __pt = static_cast<const volatile void*>(__t);
507  auto __pu = static_cast<const volatile void*>(__u);
508  if (__builtin_is_constant_evaluated())
509  return __pt <=> __pu;
510  auto __it = reinterpret_cast<__UINTPTR_TYPE__>(__pt);
511  auto __iu = reinterpret_cast<__UINTPTR_TYPE__>(__pu);
512  return __it <=> __iu;
513  }
514  else
515  return static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u);
516  }
517 
518  using is_transparent = void;
519  };
520 
521  namespace __cmp_cust
522  {
523  template<floating_point _Tp>
524  constexpr weak_ordering
525  __fp_weak_ordering(_Tp __e, _Tp __f)
526  {
527  // Returns an integer with the same sign as the argument, and magnitude
528  // indicating the classification: zero=1 subnorm=2 norm=3 inf=4 nan=5
529  auto __cat = [](_Tp __fp) -> int {
530  const int __sign = __builtin_signbit(__fp) ? -1 : 1;
531  if (__builtin_isnormal(__fp))
532  return (__fp == 0 ? 1 : 3) * __sign;
533  if (__builtin_isnan(__fp))
534  return 5 * __sign;
535  if (int __inf = __builtin_isinf_sign(__fp))
536  return 4 * __inf;
537  return 2 * __sign;
538  };
539 
540  auto __po = __e <=> __f;
541  if (is_lt(__po))
542  return weak_ordering::less;
543  else if (is_gt(__po))
544  return weak_ordering::greater;
545  else if (__po == partial_ordering::equivalent)
546  return weak_ordering::equivalent;
547  else // unordered, at least one argument is NaN
548  {
549  // return -1 for negative nan, +1 for positive nan, 0 otherwise.
550  auto __isnan_sign = [](_Tp __fp) -> int {
551  return __builtin_isnan(__fp)
552  ? __builtin_signbit(__fp) ? -1 : 1
553  : 0;
554  };
555  auto __ord = __isnan_sign(__e) <=> __isnan_sign(__f);
556  if (is_eq(__ord))
557  return weak_ordering::equivalent;
558  else if (is_lt(__ord))
559  return weak_ordering::less;
560  else
561  return weak_ordering::greater;
562  }
563  }
564 
565  template<typename _Tp, typename _Up>
566  concept __adl_strong = requires(_Tp&& __t, _Up&& __u)
567  {
568  strong_ordering(strong_order(static_cast<_Tp&&>(__t),
569  static_cast<_Up&&>(__u)));
570  };
571 
572  template<typename _Tp, typename _Up>
573  concept __adl_weak = requires(_Tp&& __t, _Up&& __u)
574  {
575  weak_ordering(weak_order(static_cast<_Tp&&>(__t),
576  static_cast<_Up&&>(__u)));
577  };
578 
579  template<typename _Tp, typename _Up>
580  concept __adl_partial = requires(_Tp&& __t, _Up&& __u)
581  {
582  partial_ordering(partial_order(static_cast<_Tp&&>(__t),
583  static_cast<_Up&&>(__u)));
584  };
585 
586  template<typename _Ord, typename _Tp, typename _Up>
587  concept __cmp3way = requires(_Tp&& __t, _Up&& __u, compare_three_way __c)
588  {
589  _Ord(__c(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)));
590  };
591 
592  template<typename _Tp, typename _Up>
593  concept __strongly_ordered
594  = __adl_strong<_Tp, _Up>
595  // FIXME: || floating_point<remove_reference_t<_Tp>>
596  || __cmp3way<strong_ordering, _Tp, _Up>;
597 
598  class _Strong_order
599  {
600  template<typename _Tp, typename _Up>
601  static constexpr bool
602  _S_noexcept()
603  {
604  if constexpr (floating_point<decay_t<_Tp>>)
605  return true;
606  else if constexpr (__adl_strong<_Tp, _Up>)
607  return noexcept(strong_ordering(strong_order(std::declval<_Tp>(),
608  std::declval<_Up>())));
609  else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>)
610  return noexcept(compare_three_way()(std::declval<_Tp>(),
611  std::declval<_Up>()));
612  }
613 
614  friend class _Weak_order;
615  friend class _Strong_fallback;
616 
617  public:
618  template<typename _Tp, typename _Up>
619  requires __strongly_ordered<_Tp, _Up>
620  constexpr strong_ordering
621  operator()(_Tp&& __e, _Up&& __f) const
622  noexcept(_S_noexcept<_Tp, _Up>())
623  {
624  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
625 
626  /* FIXME:
627  if constexpr (floating_point<decay_t<_Tp>>)
628  return __cmp_cust::__fp_strong_order(__e, __f);
629  else */ if constexpr (__adl_strong<_Tp, _Up>)
630  return strong_ordering(strong_order(static_cast<_Tp&&>(__e),
631  static_cast<_Up&&>(__f)));
632  else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>)
633  return compare_three_way()(static_cast<_Tp&&>(__e),
634  static_cast<_Up&&>(__f));
635  }
636  };
637 
638  template<typename _Tp, typename _Up>
639  concept __weakly_ordered
640  = floating_point<remove_reference_t<_Tp>>
641  || __adl_weak<_Tp, _Up>
642  || __cmp3way<weak_ordering, _Tp, _Up>
643  || __strongly_ordered<_Tp, _Up>;
644 
645  class _Weak_order
646  {
647  template<typename _Tp, typename _Up>
648  static constexpr bool
649  _S_noexcept()
650  {
651  if constexpr (floating_point<decay_t<_Tp>>)
652  return true;
653  else if constexpr (__adl_weak<_Tp, _Up>)
654  return noexcept(weak_ordering(weak_order(std::declval<_Tp>(),
655  std::declval<_Up>())));
656  else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>)
657  return noexcept(compare_three_way()(std::declval<_Tp>(),
658  std::declval<_Up>()));
659  else if constexpr (__strongly_ordered<_Tp, _Up>)
660  return _Strong_order::_S_noexcept<_Tp, _Up>();
661  }
662 
663  friend class _Partial_order;
664  friend class _Weak_fallback;
665 
666  public:
667  template<typename _Tp, typename _Up>
668  requires __weakly_ordered<_Tp, _Up>
669  constexpr weak_ordering
670  operator()(_Tp&& __e, _Up&& __f) const
671  noexcept(_S_noexcept<_Tp, _Up>())
672  {
673  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
674 
675  if constexpr (floating_point<decay_t<_Tp>>)
676  return __cmp_cust::__fp_weak_ordering(__e, __f);
677  else if constexpr (__adl_weak<_Tp, _Up>)
678  return weak_ordering(weak_order(static_cast<_Tp&&>(__e),
679  static_cast<_Up&&>(__f)));
680  else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>)
681  return compare_three_way()(static_cast<_Tp&&>(__e),
682  static_cast<_Up&&>(__f));
683  else if constexpr (__strongly_ordered<_Tp, _Up>)
684  return _Strong_order{}(static_cast<_Tp&&>(__e),
685  static_cast<_Up&&>(__f));
686  }
687  };
688 
689  template<typename _Tp, typename _Up>
690  concept __partially_ordered
691  = __adl_partial<_Tp, _Up>
692  || __cmp3way<partial_ordering, _Tp, _Up>
693  || __weakly_ordered<_Tp, _Up>;
694 
695  class _Partial_order
696  {
697  template<typename _Tp, typename _Up>
698  static constexpr bool
699  _S_noexcept()
700  {
701  if constexpr (__adl_partial<_Tp, _Up>)
702  return noexcept(partial_ordering(partial_order(std::declval<_Tp>(),
703  std::declval<_Up>())));
704  else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>)
705  return noexcept(compare_three_way()(std::declval<_Tp>(),
706  std::declval<_Up>()));
707  else if constexpr (__weakly_ordered<_Tp, _Up>)
708  return _Weak_order::_S_noexcept<_Tp, _Up>();
709  }
710 
711  friend class _Partial_fallback;
712 
713  public:
714  template<typename _Tp, typename _Up>
715  requires __partially_ordered<_Tp, _Up>
716  constexpr partial_ordering
717  operator()(_Tp&& __e, _Up&& __f) const
718  noexcept(_S_noexcept<_Tp, _Up>())
719  {
720  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
721 
722  if constexpr (__adl_partial<_Tp, _Up>)
723  return partial_ordering(partial_order(static_cast<_Tp&&>(__e),
724  static_cast<_Up&&>(__f)));
725  else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>)
726  return compare_three_way()(static_cast<_Tp&&>(__e),
727  static_cast<_Up&&>(__f));
728  else if constexpr (__weakly_ordered<_Tp, _Up>)
729  return _Weak_order{}(static_cast<_Tp&&>(__e),
730  static_cast<_Up&&>(__f));
731  }
732  };
733 
734  template<typename _Tp, typename _Up>
735  concept __op_eq_lt = requires(_Tp&& __t, _Up&& __u)
736  {
737  { static_cast<_Tp&&>(__t) == static_cast<_Up&&>(__u) }
738  -> convertible_to<bool>;
739  { static_cast<_Tp&&>(__t) < static_cast<_Up&&>(__u) }
740  -> convertible_to<bool>;
741  };
742 
743  class _Strong_fallback
744  {
745  template<typename _Tp, typename _Up>
746  static constexpr bool
747  _S_noexcept()
748  {
749  if constexpr (__strongly_ordered<_Tp, _Up>)
750  return _Strong_order::_S_noexcept<_Tp, _Up>();
751  else
752  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
753  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
754  }
755 
756  public:
757  template<typename _Tp, typename _Up>
758  requires __strongly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
759  constexpr decltype(auto)
760  operator()(_Tp&& __e, _Up&& __f) const
761  noexcept(_S_noexcept<_Tp, _Up>())
762  {
763  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
764 
765  if constexpr (__strongly_ordered<_Tp, _Up>)
766  return _Strong_order{}(static_cast<_Tp&&>(__e),
767  static_cast<_Up&&>(__f));
768  else if constexpr (__op_eq_lt<_Tp, _Up>)
769  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
770  ? strong_ordering::equal
771  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
772  ? strong_ordering::less
773  : strong_ordering::greater;
774  }
775  };
776 
777  class _Weak_fallback
778  {
779  template<typename _Tp, typename _Up>
780  static constexpr bool
781  _S_noexcept()
782  {
783  if constexpr (__weakly_ordered<_Tp, _Up>)
784  return _Weak_order::_S_noexcept<_Tp, _Up>();
785  else
786  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
787  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
788  }
789 
790  public:
791  template<typename _Tp, typename _Up>
792  requires __weakly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
793  constexpr decltype(auto)
794  operator()(_Tp&& __e, _Up&& __f) const
795  noexcept(_S_noexcept<_Tp, _Up>())
796  {
797  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
798 
799  if constexpr (__weakly_ordered<_Tp, _Up>)
800  return _Weak_order{}(static_cast<_Tp&&>(__e),
801  static_cast<_Up&&>(__f));
802  else if constexpr (__op_eq_lt<_Tp, _Up>)
803  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
804  ? weak_ordering::equivalent
805  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
806  ? weak_ordering::less
807  : weak_ordering::greater;
808  }
809  };
810 
811  class _Partial_fallback
812  {
813  template<typename _Tp, typename _Up>
814  static constexpr bool
815  _S_noexcept()
816  {
817  if constexpr (__partially_ordered<_Tp, _Up>)
818  return _Partial_order::_S_noexcept<_Tp, _Up>();
819  else
820  return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
821  && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
822  }
823 
824  public:
825  template<typename _Tp, typename _Up>
826  requires __partially_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
827  constexpr decltype(auto)
828  operator()(_Tp&& __e, _Up&& __f) const
829  noexcept(_S_noexcept<_Tp, _Up>())
830  {
831  static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
832 
833  if constexpr (__partially_ordered<_Tp, _Up>)
834  return _Partial_order{}(static_cast<_Tp&&>(__e),
835  static_cast<_Up&&>(__f));
836  else if constexpr (__op_eq_lt<_Tp, _Up>)
837  return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
838  ? partial_ordering::equivalent
839  : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
840  ? partial_ordering::less
841  : static_cast<_Up&&>(__f) < static_cast<_Tp&&>(__e)
842  ? partial_ordering::greater
843  : partial_ordering::unordered;
844  }
845  };
846  } // namespace __cmp_cust
847 
848  // [cmp.alg], comparison algorithms
849  inline namespace __cmp_alg
850  {
851  inline constexpr __cmp_cust::_Strong_order strong_order{};
852 
853  inline constexpr __cmp_cust::_Weak_order weak_order{};
854 
855  inline constexpr __cmp_cust::_Partial_order partial_order{};
856 
857  inline constexpr __cmp_cust::_Strong_fallback
858  compare_strong_order_fallback{};
859 
860  inline constexpr __cmp_cust::_Weak_fallback
861  compare_weak_order_fallback{};
862 
863  inline constexpr __cmp_cust::_Partial_fallback
864  compare_partial_order_fallback{};
865  }
866 
867  namespace __detail
868  {
869  // [expos.only.func] synth-three-way
870  inline constexpr struct _Synth3way
871  {
872  template<typename _Tp, typename _Up>
873  static constexpr bool
874  _S_noexcept(const _Tp* __t = nullptr, const _Up* __u = nullptr)
875  {
876  if constexpr (three_way_comparable_with<_Tp, _Up>)
877  return noexcept(*__t <=> *__u);
878  else
879  return noexcept(*__t < *__u) && noexcept(*__u < *__t);
880  }
881 
882  template<typename _Tp, typename _Up>
883  constexpr auto
884  operator()(const _Tp& __t, const _Up& __u) const
885  noexcept(_S_noexcept<_Tp, _Up>())
886  requires requires
887  {
888  { __t < __u } -> __boolean_testable;
889  { __u < __t } -> __boolean_testable;
890  }
891  {
892  if constexpr (three_way_comparable_with<_Tp, _Up>)
893  return __t <=> __u;
894  else
895  {
896  if (__t < __u)
897  return weak_ordering::less;
898  else if (__u < __t)
899  return weak_ordering::greater;
900  else
901  return weak_ordering::equivalent;
902  }
903  }
904  } __synth3way = {};
905 
906  // [expos.only.func] synth-three-way-result
907  template<typename _Tp, typename _Up = _Tp>
908  using __synth3way_t
909  = decltype(__detail::__synth3way(std::declval<_Tp&>(),
910  std::declval<_Up&>()));
911  } // namespace __detail
912 #endif // concepts
913 } // namespace std
914 
915 #pragma GCC visibility pop
916 
917 #endif // C++20
918 
919 #endif // _COMPARE
typename remove_reference< _Tp >::type remove_reference_t
Alias template for remove_reference.
Definition: type_traits:1635