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compare
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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
45namespace 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 } // 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 = three_way_comparable_with<_Tp, _Up>
485 && convertible_to<_Tp, const volatile void*>
486 && convertible_to<_Up, const volatile void*>
487 && ! requires(_Tp&& __t, _Up&& __u)
488 { operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
489 && ! requires(_Tp&& __t, _Up&& __u)
490 { static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); };
491 } // namespace __detail
492
493 // [cmp.object], typename compare_three_way
494 struct compare_three_way
495 {
496 template<typename _Tp, typename _Up>
497 requires three_way_comparable_with<_Tp, _Up>
498 constexpr auto
499 operator()(_Tp&& __t, _Up&& __u) const
500 noexcept(noexcept(std::declval<_Tp>() <=> std::declval<_Up>()))
501 {
502 if constexpr (__detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
503 {
504 auto __pt = static_cast<const volatile void*>(__t);
505 auto __pu = static_cast<const volatile void*>(__u);
506 if (__builtin_is_constant_evaluated())
507 return __pt <=> __pu;
508 auto __it = reinterpret_cast<__UINTPTR_TYPE__>(__pt);
509 auto __iu = reinterpret_cast<__UINTPTR_TYPE__>(__pu);
510 return __it <=> __iu;
511 }
512 else
513 return static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u);
514 }
515
516 using is_transparent = void;
517 };
518
519 namespace __cmp_cust
520 {
521 template<floating_point _Tp>
522 constexpr weak_ordering
523 __fp_weak_ordering(_Tp __e, _Tp __f)
524 {
525 // Returns an integer with the same sign as the argument, and magnitude
526 // indicating the classification: zero=1 subnorm=2 norm=3 inf=4 nan=5
527 auto __cat = [](_Tp __fp) -> int {
528 const int __sign = __builtin_signbit(__fp) ? -1 : 1;
529 if (__builtin_isnormal(__fp))
530 return (__fp == 0 ? 1 : 3) * __sign;
531 if (__builtin_isnan(__fp))
532 return 5 * __sign;
533 if (int __inf = __builtin_isinf_sign(__fp))
534 return 4 * __inf;
535 return 2 * __sign;
536 };
537
538 auto __po = __e <=> __f;
539 if (is_lt(__po))
540 return weak_ordering::less;
541 else if (is_gt(__po))
542 return weak_ordering::greater;
543 else if (__po == partial_ordering::equivalent)
544 return weak_ordering::equivalent;
545 else // unordered, at least one argument is NaN
546 {
547 // return -1 for negative nan, +1 for positive nan, 0 otherwise.
548 auto __isnan_sign = [](_Tp __fp) -> int {
549 return __builtin_isnan(__fp)
550 ? __builtin_signbit(__fp) ? -1 : 1
551 : 0;
552 };
553 auto __ord = __isnan_sign(__e) <=> __isnan_sign(__f);
554 if (is_eq(__ord))
555 return weak_ordering::equivalent;
556 else if (is_lt(__ord))
557 return weak_ordering::less;
558 else
559 return weak_ordering::greater;
560 }
561 }
562
563 template<typename _Tp, typename _Up>
564 concept __adl_strong = requires(_Tp&& __t, _Up&& __u)
565 {
566 strong_ordering(strong_order(static_cast<_Tp&&>(__t),
567 static_cast<_Up&&>(__u)));
568 };
569
570 template<typename _Tp, typename _Up>
571 concept __adl_weak = requires(_Tp&& __t, _Up&& __u)
572 {
573 weak_ordering(weak_order(static_cast<_Tp&&>(__t),
574 static_cast<_Up&&>(__u)));
575 };
576
577 template<typename _Tp, typename _Up>
578 concept __adl_partial = requires(_Tp&& __t, _Up&& __u)
579 {
580 partial_ordering(partial_order(static_cast<_Tp&&>(__t),
581 static_cast<_Up&&>(__u)));
582 };
583
584 template<typename _Ord, typename _Tp, typename _Up>
585 concept __cmp3way = requires(_Tp&& __t, _Up&& __u, compare_three_way __c)
586 {
587 _Ord(__c(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)));
588 };
589
590 template<typename _Tp, typename _Up>
591 concept __strongly_ordered
592 = __adl_strong<_Tp, _Up>
593 // FIXME: || floating_point<remove_reference_t<_Tp>>
594 || __cmp3way<strong_ordering, _Tp, _Up>;
595
596 class _Strong_order
597 {
598 template<typename _Tp, typename _Up>
599 static constexpr bool
600 _S_noexcept()
601 {
602 if constexpr (floating_point<decay_t<_Tp>>)
603 return true;
604 else if constexpr (__adl_strong<_Tp, _Up>)
605 return noexcept(strong_ordering(strong_order(std::declval<_Tp>(),
606 std::declval<_Up>())));
607 else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>)
608 return noexcept(compare_three_way()(std::declval<_Tp>(),
609 std::declval<_Up>()));
610 }
611
612 friend class _Weak_order;
613 friend class _Strong_fallback;
614
615 public:
616 template<typename _Tp, typename _Up>
617 requires __strongly_ordered<_Tp, _Up>
618 constexpr strong_ordering
619 operator()(_Tp&& __e, _Up&& __f) const
620 noexcept(_S_noexcept<_Tp, _Up>())
621 {
622 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
623
624 /* FIXME:
625 if constexpr (floating_point<decay_t<_Tp>>)
626 return __cmp_cust::__fp_strong_order(__e, __f);
627 else */ if constexpr (__adl_strong<_Tp, _Up>)
628 return strong_ordering(strong_order(static_cast<_Tp&&>(__e),
629 static_cast<_Up&&>(__f)));
630 else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>)
631 return compare_three_way()(static_cast<_Tp&&>(__e),
632 static_cast<_Up&&>(__f));
633 }
634 };
635
636 template<typename _Tp, typename _Up>
637 concept __weakly_ordered
638 = floating_point<remove_reference_t<_Tp>>
639 || __adl_weak<_Tp, _Up>
640 || __cmp3way<weak_ordering, _Tp, _Up>
641 || __strongly_ordered<_Tp, _Up>;
642
643 class _Weak_order
644 {
645 template<typename _Tp, typename _Up>
646 static constexpr bool
647 _S_noexcept()
648 {
649 if constexpr (floating_point<decay_t<_Tp>>)
650 return true;
651 else if constexpr (__adl_weak<_Tp, _Up>)
652 return noexcept(weak_ordering(weak_order(std::declval<_Tp>(),
653 std::declval<_Up>())));
654 else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>)
655 return noexcept(compare_three_way()(std::declval<_Tp>(),
656 std::declval<_Up>()));
657 else if constexpr (__strongly_ordered<_Tp, _Up>)
658 return _Strong_order::_S_noexcept<_Tp, _Up>();
659 }
660
661 friend class _Partial_order;
662 friend class _Weak_fallback;
663
664 public:
665 template<typename _Tp, typename _Up>
666 requires __weakly_ordered<_Tp, _Up>
667 constexpr weak_ordering
668 operator()(_Tp&& __e, _Up&& __f) const
669 noexcept(_S_noexcept<_Tp, _Up>())
670 {
671 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
672
673 if constexpr (floating_point<decay_t<_Tp>>)
674 return __cmp_cust::__fp_weak_ordering(__e, __f);
675 else if constexpr (__adl_weak<_Tp, _Up>)
676 return weak_ordering(weak_order(static_cast<_Tp&&>(__e),
677 static_cast<_Up&&>(__f)));
678 else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>)
679 return compare_three_way()(static_cast<_Tp&&>(__e),
680 static_cast<_Up&&>(__f));
681 else if constexpr (__strongly_ordered<_Tp, _Up>)
682 return _Strong_order{}(static_cast<_Tp&&>(__e),
683 static_cast<_Up&&>(__f));
684 }
685 };
686
687 template<typename _Tp, typename _Up>
688 concept __partially_ordered
689 = __adl_partial<_Tp, _Up>
690 || __cmp3way<partial_ordering, _Tp, _Up>
691 || __weakly_ordered<_Tp, _Up>;
692
693 class _Partial_order
694 {
695 template<typename _Tp, typename _Up>
696 static constexpr bool
697 _S_noexcept()
698 {
699 if constexpr (__adl_partial<_Tp, _Up>)
700 return noexcept(partial_ordering(partial_order(std::declval<_Tp>(),
701 std::declval<_Up>())));
702 else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>)
703 return noexcept(compare_three_way()(std::declval<_Tp>(),
704 std::declval<_Up>()));
705 else if constexpr (__weakly_ordered<_Tp, _Up>)
706 return _Weak_order::_S_noexcept<_Tp, _Up>();
707 }
708
709 friend class _Partial_fallback;
710
711 public:
712 template<typename _Tp, typename _Up>
713 requires __partially_ordered<_Tp, _Up>
714 constexpr partial_ordering
715 operator()(_Tp&& __e, _Up&& __f) const
716 noexcept(_S_noexcept<_Tp, _Up>())
717 {
718 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
719
720 if constexpr (__adl_partial<_Tp, _Up>)
721 return partial_ordering(partial_order(static_cast<_Tp&&>(__e),
722 static_cast<_Up&&>(__f)));
723 else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>)
724 return compare_three_way()(static_cast<_Tp&&>(__e),
725 static_cast<_Up&&>(__f));
726 else if constexpr (__weakly_ordered<_Tp, _Up>)
727 return _Weak_order{}(static_cast<_Tp&&>(__e),
728 static_cast<_Up&&>(__f));
729 }
730 };
731
732 template<typename _Tp, typename _Up>
733 concept __op_eq_lt = requires(_Tp&& __t, _Up&& __u)
734 {
735 { static_cast<_Tp&&>(__t) == static_cast<_Up&&>(__u) }
736 -> convertible_to<bool>;
737 { static_cast<_Tp&&>(__t) < static_cast<_Up&&>(__u) }
738 -> convertible_to<bool>;
739 };
740
741 class _Strong_fallback
742 {
743 template<typename _Tp, typename _Up>
744 static constexpr bool
745 _S_noexcept()
746 {
747 if constexpr (__strongly_ordered<_Tp, _Up>)
748 return _Strong_order::_S_noexcept<_Tp, _Up>();
749 else
750 return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
751 && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
752 }
753
754 public:
755 template<typename _Tp, typename _Up>
756 requires __strongly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
757 constexpr decltype(auto)
758 operator()(_Tp&& __e, _Up&& __f) const
759 noexcept(_S_noexcept<_Tp, _Up>())
760 {
761 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
762
763 if constexpr (__strongly_ordered<_Tp, _Up>)
764 return _Strong_order{}(static_cast<_Tp&&>(__e),
765 static_cast<_Up&&>(__f));
766 else if constexpr (__op_eq_lt<_Tp, _Up>)
767 return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
768 ? strong_ordering::equal
769 : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
770 ? strong_ordering::less
771 : strong_ordering::greater;
772 }
773 };
774
775 class _Weak_fallback
776 {
777 template<typename _Tp, typename _Up>
778 static constexpr bool
779 _S_noexcept()
780 {
781 if constexpr (__weakly_ordered<_Tp, _Up>)
782 return _Weak_order::_S_noexcept<_Tp, _Up>();
783 else
784 return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
785 && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
786 }
787
788 public:
789 template<typename _Tp, typename _Up>
790 requires __weakly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
791 constexpr decltype(auto)
792 operator()(_Tp&& __e, _Up&& __f) const
793 noexcept(_S_noexcept<_Tp, _Up>())
794 {
795 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
796
797 if constexpr (__weakly_ordered<_Tp, _Up>)
798 return _Weak_order{}(static_cast<_Tp&&>(__e),
799 static_cast<_Up&&>(__f));
800 else if constexpr (__op_eq_lt<_Tp, _Up>)
801 return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
802 ? weak_ordering::equivalent
803 : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
804 ? weak_ordering::less
805 : weak_ordering::greater;
806 }
807 };
808
809 class _Partial_fallback
810 {
811 template<typename _Tp, typename _Up>
812 static constexpr bool
813 _S_noexcept()
814 {
815 if constexpr (__partially_ordered<_Tp, _Up>)
816 return _Partial_order::_S_noexcept<_Tp, _Up>();
817 else
818 return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>()))
819 && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>()));
820 }
821
822 public:
823 template<typename _Tp, typename _Up>
824 requires __partially_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up>
825 constexpr decltype(auto)
826 operator()(_Tp&& __e, _Up&& __f) const
827 noexcept(_S_noexcept<_Tp, _Up>())
828 {
829 static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>);
830
831 if constexpr (__partially_ordered<_Tp, _Up>)
832 return _Partial_order{}(static_cast<_Tp&&>(__e),
833 static_cast<_Up&&>(__f));
834 else if constexpr (__op_eq_lt<_Tp, _Up>)
835 return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f)
836 ? partial_ordering::equivalent
837 : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f)
838 ? partial_ordering::less
839 : static_cast<_Up&&>(__f) < static_cast<_Tp&&>(__e)
840 ? partial_ordering::greater
841 : partial_ordering::unordered;
842 }
843 };
844 } // namespace __cmp_cust
845
846 // [cmp.alg], comparison algorithms
847 inline namespace __cmp_alg
848 {
849 inline constexpr __cmp_cust::_Strong_order strong_order{};
850
851 inline constexpr __cmp_cust::_Weak_order weak_order{};
852
853 inline constexpr __cmp_cust::_Partial_order partial_order{};
854
855 inline constexpr __cmp_cust::_Strong_fallback
856 compare_strong_order_fallback{};
857
858 inline constexpr __cmp_cust::_Weak_fallback
859 compare_weak_order_fallback{};
860
861 inline constexpr __cmp_cust::_Partial_fallback
862 compare_partial_order_fallback{};
863 }
864
865 namespace __detail
866 {
867 // [expos.only.func]
868 inline constexpr struct _Synth3way
869 {
870 template<typename _Tp, typename _Up>
871 constexpr auto
872 operator()(const _Tp& __t, const _Up& __u) const
873 requires requires
874 {
875 { __t < __u } -> __boolean_testable;
876 { __u < __t } -> __boolean_testable;
877 }
878 {
879 if constexpr (three_way_comparable_with<_Tp, _Up>)
880 return __t <=> __u;
881 else
882 {
883 if (__t < __u)
884 return weak_ordering::less;
885 else if (__u < __t)
886 return weak_ordering::greater;
887 else
888 return weak_ordering::equivalent;
889 }
890 }
891 } __synth3way = {};
892
893 template<typename _Tp, typename _Up = _Tp>
894 using __synth3way_t
895 = decltype(__detail::__synth3way(std::declval<_Tp&>(),
896 std::declval<_Up&>()));
897 } // namespace __detail
898#endif // concepts
899} // namespace std
900
901#pragma GCC visibility pop
902
903#endif // C++20
904
905#endif // _COMPARE
ISO C++ entities toplevel namespace is std.