1	// <chrono> -*- C++ -*-
2
3	// Copyright (C) 2008-2021 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/chrono
26	* This is a Standard C++ Library header.
27	* @ingroup chrono
28	*/
29
30	#ifndef _GLIBCXX_CHRONO
31	#define _GLIBCXX_CHRONO 1
32
33	#pragma GCC system_header
34
35	#if __cplusplus < 201103L
36	# include <bits/c++0x_warning.h>
37	#else
38
39	#include <ratio>
40	#include <type_traits>
41	#include <limits>
42	#include <ctime>
43	#include <bits/parse_numbers.h> // for literals support.
44	#if __cplusplus > 201703L
45	# include <concepts>
46	# include <compare>
47	#endif
48
49	namespace std _GLIBCXX_VISIBILITY(default)
50	{
51	_GLIBCXX_BEGIN_NAMESPACE_VERSION
52
53	#if __cplusplus >= 201703L
54	namespace filesystem { struct __file_clock; };
55	#endif
56
57	/**
58	* @defgroup chrono Time
59	* @ingroup utilities
60	*
61	* Classes and functions for time.
62	*
63	* @since C++11
64	*/
65
66	/** @namespace std::chrono
67	* @brief ISO C++ 2011 namespace for date and time utilities
68	* @ingroup chrono
69	*/
70	namespace chrono
71	{
72	/// @addtogroup chrono
73	/// @{
74
75	/// `chrono::duration` represents a distance between two points in time
76	template<typename _Rep, typename _Period = ratio<1>>
77	struct duration;
78
79	/// `chrono::time_point` represents a point in time as measured by a clock
80	template<typename _Clock, typename _Dur = typename _Clock::duration>
81	struct time_point;
82	/// @}
83	}
84
85	/// @addtogroup chrono
86	/// @{
87
88	// 20.11.4.3 specialization of common_type (for duration, sfinae-friendly)
89
90	/// @cond undocumented
91
92	template<typename _CT, typename _Period1, typename _Period2, typename = void>
93	struct __duration_common_type
94	{ };
95
96	template<typename _CT, typename _Period1, typename _Period2>
97	struct __duration_common_type<_CT, _Period1, _Period2,
98	__void_t<typename _CT::type>>
99	{
100	private:
101	using __gcd_num = __static_gcd<_Period1::num, _Period2::num>;
102	using __gcd_den = __static_gcd<_Period1::den, _Period2::den>;
103	using __cr = typename _CT::type;
104	using __r = ratio<__gcd_num::value,
105	(_Period1::den / __gcd_den::value) * _Period2::den>;
106
107	public:
108	using type = chrono::duration<__cr, typename __r::type>;
109	};
110
111	/// @endcond
112
113	/// @{
114	/// @relates chrono::duration
115
116	/// Specialization of common_type for chrono::duration types.
117	template<typename _Rep1, typename _Period1, typename _Rep2, typename _Period2>
118	struct common_type<chrono::duration<_Rep1, _Period1>,
119	chrono::duration<_Rep2, _Period2>>
120	: __duration_common_type<common_type<_Rep1, _Rep2>,
121	typename _Period1::type,
122	typename _Period2::type>
123	{ };
124
125	/// Specialization of common_type for two identical chrono::duration types.
126	template<typename _Rep, typename _Period>
127	struct common_type<chrono::duration<_Rep, _Period>,
128	chrono::duration<_Rep, _Period>>
129	{
130	using type = chrono::duration<typename common_type<_Rep>::type,
131	typename _Period::type>;
132	};
133
134	/// Specialization of common_type for one chrono::duration type.
135	template<typename _Rep, typename _Period>
136	struct common_type<chrono::duration<_Rep, _Period>>
137	{
138	using type = chrono::duration<typename common_type<_Rep>::type,
139	typename _Period::type>;
140	};
141	/// @}
142
143	// 20.11.4.3 specialization of common_type (for time_point, sfinae-friendly)
144
145	/// @cond undocumented
146
147	template<typename _CT, typename _Clock, typename = void>
148	struct __timepoint_common_type
149	{ };
150
151	template<typename _CT, typename _Clock>
152	struct __timepoint_common_type<_CT, _Clock, __void_t<typename _CT::type>>
153	{
154	using type = chrono::time_point<_Clock, typename _CT::type>;
155	};
156
157	/// @endcond
158
159	/// @{
160	/// @relates chrono::time_point
161
162	/// Specialization of common_type for chrono::time_point types.
163	template<typename _Clock, typename _Duration1, typename _Duration2>
164	struct common_type<chrono::time_point<_Clock, _Duration1>,
165	chrono::time_point<_Clock, _Duration2>>
166	: __timepoint_common_type<common_type<_Duration1, _Duration2>, _Clock>
167	{ };
168
169	/// Specialization of common_type for two identical chrono::time_point types.
170	template<typename _Clock, typename _Duration>
171	struct common_type<chrono::time_point<_Clock, _Duration>,
172	chrono::time_point<_Clock, _Duration>>
173	{ using type = chrono::time_point<_Clock, _Duration>; };
174
175	/// Specialization of common_type for one chrono::time_point type.
176	template<typename _Clock, typename _Duration>
177	struct common_type<chrono::time_point<_Clock, _Duration>>
178	{ using type = chrono::time_point<_Clock, _Duration>; };
179	/// @}
180
181	/// @} group chrono
182
183	namespace chrono
184	{
185	/// @addtogroup chrono
186	/// @{
187
188	/// @cond undocumented
189
190	// Primary template for duration_cast impl.
191	template<typename _ToDur, typename _CF, typename _CR,
192	bool _NumIsOne = false, bool _DenIsOne = false>
193	struct __duration_cast_impl
194	{
195	template<typename _Rep, typename _Period>
196	static constexpr _ToDur
197	__cast(const duration<_Rep, _Period>& __d)
198	{
199	typedef typename _ToDur::rep __to_rep;
200	return _ToDur(static_cast<__to_rep>(static_cast<_CR>(__d.count())
201	* static_cast<_CR>(_CF::num)
202	/ static_cast<_CR>(_CF::den)));
203	}
204	};
205
206	template<typename _ToDur, typename _CF, typename _CR>
207	struct __duration_cast_impl<_ToDur, _CF, _CR, true, true>
208	{
209	template<typename _Rep, typename _Period>
210	static constexpr _ToDur
211	__cast(const duration<_Rep, _Period>& __d)
212	{
213	typedef typename _ToDur::rep __to_rep;
214	return _ToDur(static_cast<__to_rep>(__d.count()));
215	}
216	};
217
218	template<typename _ToDur, typename _CF, typename _CR>
219	struct __duration_cast_impl<_ToDur, _CF, _CR, true, false>
220	{
221	template<typename _Rep, typename _Period>
222	static constexpr _ToDur
223	__cast(const duration<_Rep, _Period>& __d)
224	{
225	typedef typename _ToDur::rep __to_rep;
226	return _ToDur(static_cast<__to_rep>(
227	static_cast<_CR>(__d.count()) / static_cast<_CR>(_CF::den)));
228	}
229	};
230
231	template<typename _ToDur, typename _CF, typename _CR>
232	struct __duration_cast_impl<_ToDur, _CF, _CR, false, true>
233	{
234	template<typename _Rep, typename _Period>
235	static constexpr _ToDur
236	__cast(const duration<_Rep, _Period>& __d)
237	{
238	typedef typename _ToDur::rep __to_rep;
239	return _ToDur(static_cast<__to_rep>(
240	static_cast<_CR>(__d.count()) * static_cast<_CR>(_CF::num)));
241	}
242	};
243
244	template<typename _Tp>
245	struct __is_duration
246	: std::false_type
247	{ };
248
249	template<typename _Rep, typename _Period>
250	struct __is_duration<duration<_Rep, _Period>>
251	: std::true_type
252	{ };
253
254	template<typename _Tp>
255	using __enable_if_is_duration
256	= typename enable_if<__is_duration<_Tp>::value, _Tp>::type;
257
258	template<typename _Tp>
259	using __disable_if_is_duration
260	= typename enable_if<!__is_duration<_Tp>::value, _Tp>::type;
261
262	/// @endcond
263
264	/// duration_cast
265	template<typename _ToDur, typename _Rep, typename _Period>
266	constexpr __enable_if_is_duration<_ToDur>
267	duration_cast(const duration<_Rep, _Period>& __d)
268	{
269	typedef typename _ToDur::period __to_period;
270	typedef typename _ToDur::rep __to_rep;
271	typedef ratio_divide<_Period, __to_period> __cf;
272	typedef typename common_type<__to_rep, _Rep, intmax_t>::type
273	__cr;
274	typedef __duration_cast_impl<_ToDur, __cf, __cr,
275	__cf::num == 1, __cf::den == 1> __dc;
276	return __dc::__cast(__d);
277	}
278
279	/// treat_as_floating_point
280	template<typename _Rep>
281	struct treat_as_floating_point
282	: is_floating_point<_Rep>
283	{ };
284
285	#if __cplusplus > 201402L
286	template <typename _Rep>
287	inline constexpr bool treat_as_floating_point_v =
288	treat_as_floating_point<_Rep>::value;
289	#endif // C++17
290
291	#if __cplusplus > 201703L
292	template<typename _Tp>
293	struct is_clock;
294
295	template<typename _Tp>
296	inline constexpr bool is_clock_v = is_clock<_Tp>::value;
297
298	#if __cpp_lib_concepts
299	template<typename _Tp>
300	struct is_clock : false_type
301	{ };
302
303	template<typename _Tp>
304	requires requires {
305	typename _Tp::rep;
306	typename _Tp::period;
307	typename _Tp::duration;
308	typename _Tp::time_point::clock;
309	typename _Tp::time_point::duration;
310	{ &_Tp::is_steady } -> same_as<const bool*>;
311	{ _Tp::now() } -> same_as<typename _Tp::time_point>;
312	requires same_as<typename _Tp::duration,
313	duration<typename _Tp::rep, typename _Tp::period>>;
314	requires same_as<typename _Tp::time_point::duration,
315	typename _Tp::duration>;
316	}
317	struct is_clock<_Tp> : true_type
318	{ };
319	#else
320	template<typename _Tp, typename = void>
321	struct __is_clock_impl : false_type
322	{ };
323
324	template<typename _Tp>
325	struct __is_clock_impl<_Tp,
326	void_t<typename _Tp::rep, typename _Tp::period,
327	typename _Tp::duration,
328	typename _Tp::time_point::duration,
329	decltype(_Tp::is_steady),
330	decltype(_Tp::now())>>
331	: __and_<is_same<typename _Tp::duration,
332	duration<typename _Tp::rep, typename _Tp::period>>,
333	is_same<typename _Tp::time_point::duration,
334	typename _Tp::duration>,
335	is_same<decltype(&_Tp::is_steady), const bool*>,
336	is_same<decltype(_Tp::now()), typename _Tp::time_point>>::type
337	{ };
338
339	template<typename _Tp>
340	struct is_clock : __is_clock_impl<_Tp>::type
341	{ };
342	#endif
343	#endif // C++20
344
345	#if __cplusplus >= 201703L
346	# define __cpp_lib_chrono 201611
347
348	template<typename _ToDur, typename _Rep, typename _Period>
349	constexpr __enable_if_is_duration<_ToDur>
350	floor(const duration<_Rep, _Period>& __d)
351	{
352	auto __to = chrono::duration_cast<_ToDur>(__d);
353	if (__to > __d)
354	return __to - _ToDur{1};
355	return __to;
356	}
357
358	template<typename _ToDur, typename _Rep, typename _Period>
359	constexpr __enable_if_is_duration<_ToDur>
360	ceil(const duration<_Rep, _Period>& __d)
361	{
362	auto __to = chrono::duration_cast<_ToDur>(__d);
363	if (__to < __d)
364	return __to + _ToDur{1};
365	return __to;
366	}
367
368	template <typename _ToDur, typename _Rep, typename _Period>
369	constexpr enable_if_t<
370	__and_<__is_duration<_ToDur>,
371	__not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
372	_ToDur>
373	round(const duration<_Rep, _Period>& __d)
374	{
375	_ToDur __t0 = chrono::floor<_ToDur>(__d);
376	_ToDur __t1 = __t0 + _ToDur{1};
377	auto __diff0 = __d - __t0;
378	auto __diff1 = __t1 - __d;
379	if (__diff0 == __diff1)
380	{
381	if (__t0.count() & 1)
382	return __t1;
383	return __t0;
384	}
385	else if (__diff0 < __diff1)
386	return __t0;
387	return __t1;
388	}
389
390	template<typename _Rep, typename _Period>
391	constexpr
392	enable_if_t<numeric_limits<_Rep>::is_signed, duration<_Rep, _Period>>
393	abs(duration<_Rep, _Period> __d)
394	{
395	if (__d >= __d.zero())
396	return __d;
397	return -__d;
398	}
399
400	// Make chrono::ceil<D> also usable as chrono::__detail::ceil<D>.
401	namespace __detail { using chrono::ceil; }
402
403	#else // ! C++17
404
405	// We want to use ceil even when compiling for earlier standards versions.
406	// C++11 only allows a single statement in a constexpr function, so we
407	// need to move the comparison into a separate function, __ceil_impl.
408	namespace __detail
409	{
410	template<typename _Tp, typename _Up>
411	constexpr _Tp
412	__ceil_impl(const _Tp& __t, const _Up& __u)
413	{
414	return (__t < __u) ? (__t + _Tp{1}) : __t;
415	}
416
417	// C++11-friendly version of std::chrono::ceil<D> for internal use.
418	template<typename _ToDur, typename _Rep, typename _Period>
419	constexpr _ToDur
420	ceil(const duration<_Rep, _Period>& __d)
421	{
422	return __detail::__ceil_impl(chrono::duration_cast<_ToDur>(__d), __d);
423	}
424	}
425	#endif // C++17
426
427	/// duration_values
428	template<typename _Rep>
429	struct duration_values
430	{
431	static constexpr _Rep
432	zero() noexcept
433	{ return _Rep(0); }
434
435	static constexpr _Rep
436	max() noexcept
437	{ return numeric_limits<_Rep>::max(); }
438
439	static constexpr _Rep
440	min() noexcept
441	{ return numeric_limits<_Rep>::lowest(); }
442	};
443
444	/// @cond undocumented
445
446	template<typename _Tp>
447	struct __is_ratio
448	: std::false_type
449	{ };
450
451	template<intmax_t _Num, intmax_t _Den>
452	struct __is_ratio<ratio<_Num, _Den>>
453	: std::true_type
454	{ };
455
456	/// @endcond
457
458	template<typename _Rep, typename _Period>
459	struct duration
460	{
461	private:
462	template<typename _Rep2>
463	using __is_float = treat_as_floating_point<_Rep2>;
464
465	static constexpr intmax_t
466	_S_gcd(intmax_t __m, intmax_t __n) noexcept
467	{
468	// Duration only allows positive periods so we don't need to
469	// handle negative values here (unlike __static_gcd and std::gcd).
470	#if __cplusplus >= 201402L
471	do
472	{
473	intmax_t __rem = __m % __n;
474	__m = __n;
475	__n = __rem;
476	}
477	while (__n != 0);
478	return __m;
479	#else
480	// C++11 doesn't allow loops in constexpr functions, but this
481	// recursive version can be more expensive to evaluate.
482	return (__n == 0) ? __m : _S_gcd(__n, __m % __n);
483	#endif
484	}
485
486	// _GLIBCXX_RESOLVE_LIB_DEFECTS
487	// 2094. overflow shouldn't participate in overload resolution
488	// 3090. What is [2094] intended to mean?
489	// This only produces a valid type if no overflow occurs.
490	template<typename _R1, typename _R2,
491	intmax_t __gcd1 = _S_gcd(m: _R1::num, n: _R2::num),
492	intmax_t __gcd2 = _S_gcd(m: _R1::den, n: _R2::den)>
493	using __divide = ratio<(_R1::num / __gcd1) * (_R2::den / __gcd2),
494	(_R1::den / __gcd2) * (_R2::num / __gcd1)>;
495
496	// _Period2 is an exact multiple of _Period
497	template<typename _Period2>
498	using __is_harmonic
499	= __bool_constant<__divide<_Period2, _Period>::den == 1>;
500
501	public:
502
503	using rep = _Rep;
504	using period = typename _Period::type;
505
506	static_assert(!__is_duration<_Rep>::value, "rep cannot be a duration");
507	static_assert(__is_ratio<_Period>::value,
508	"period must be a specialization of ratio");
509	static_assert(_Period::num > 0, "period must be positive");
510
511	// 20.11.5.1 construction / copy / destroy
512	constexpr duration() = default;
513
514	duration(const duration&) = default;
515
516	// _GLIBCXX_RESOLVE_LIB_DEFECTS
517	// 3050. Conversion specification problem in chrono::duration
518	template<typename _Rep2, typename = _Require<
519	is_convertible<const _Rep2&, rep>,
520	__or_<__is_float<rep>, __not_<__is_float<_Rep2>>>>>
521	constexpr explicit duration(const _Rep2& __rep)
522	: __r(static_cast<rep>(__rep)) { }
523
524	template<typename _Rep2, typename _Period2, typename = _Require<
525	is_convertible<const _Rep2&, rep>,
526	__or_<__is_float<rep>,
527	__and_<__is_harmonic<_Period2>,
528	__not_<__is_float<_Rep2>>>>>>
529	constexpr duration(const duration<_Rep2, _Period2>& __d)
530	: __r(duration_cast<duration>(__d).count()) { }
531
532	~duration() = default;
533	duration& operator=(const duration&) = default;
534
535	// 20.11.5.2 observer
536	constexpr rep
537	count() const
538	{ return __r; }
539
540	// 20.11.5.3 arithmetic
541
542	constexpr duration<typename common_type<rep>::type, period>
543	operator+() const
544	{ return duration<typename common_type<rep>::type, period>(__r); }
545
546	constexpr duration<typename common_type<rep>::type, period>
547	operator-() const
548	{ return duration<typename common_type<rep>::type, period>(-__r); }
549
550	_GLIBCXX17_CONSTEXPR duration&
551	operator++()
552	{
553	++__r;
554	return *this;
555	}
556
557	_GLIBCXX17_CONSTEXPR duration
558	operator++(int)
559	{ return duration(__r++); }
560
561	_GLIBCXX17_CONSTEXPR duration&
562	operator--()
563	{
564	--__r;
565	return *this;
566	}
567
568	_GLIBCXX17_CONSTEXPR duration
569	operator--(int)
570	{ return duration(__r--); }
571
572	_GLIBCXX17_CONSTEXPR duration&
573	operator+=(const duration& __d)
574	{
575	__r += __d.count();
576	return *this;
577	}
578
579	_GLIBCXX17_CONSTEXPR duration&
580	operator-=(const duration& __d)
581	{
582	__r -= __d.count();
583	return *this;
584	}
585
586	_GLIBCXX17_CONSTEXPR duration&
587	operator*=(const rep& __rhs)
588	{
589	__r *= __rhs;
590	return *this;
591	}
592
593	_GLIBCXX17_CONSTEXPR duration&
594	operator/=(const rep& __rhs)
595	{
596	__r /= __rhs;
597	return *this;
598	}
599
600	// DR 934.
601	template<typename _Rep2 = rep>
602	_GLIBCXX17_CONSTEXPR
603	typename enable_if<!treat_as_floating_point<_Rep2>::value,
604	duration&>::type
605	operator%=(const rep& __rhs)
606	{
607	__r %= __rhs;
608	return *this;
609	}
610
611	template<typename _Rep2 = rep>
612	_GLIBCXX17_CONSTEXPR
613	typename enable_if<!treat_as_floating_point<_Rep2>::value,
614	duration&>::type
615	operator%=(const duration& __d)
616	{
617	__r %= __d.count();
618	return *this;
619	}
620
621	// 20.11.5.4 special values
622	static constexpr duration
623	zero() noexcept
624	{ return duration(duration_values<rep>::zero()); }
625
626	static constexpr duration
627	min() noexcept
628	{ return duration(duration_values<rep>::min()); }
629
630	static constexpr duration
631	max() noexcept
632	{ return duration(duration_values<rep>::max()); }
633
634	private:
635	rep __r;
636	};
637
638	/// @{
639	/// @relates std::chrono::duration
640
641	/// The sum of two durations.
642	template<typename _Rep1, typename _Period1,
643	typename _Rep2, typename _Period2>
644	constexpr typename common_type<duration<_Rep1, _Period1>,
645	duration<_Rep2, _Period2>>::type
646	operator+(const duration<_Rep1, _Period1>& __lhs,
647	const duration<_Rep2, _Period2>& __rhs)
648	{
649	typedef duration<_Rep1, _Period1> __dur1;
650	typedef duration<_Rep2, _Period2> __dur2;
651	typedef typename common_type<__dur1,__dur2>::type __cd;
652	return __cd(__cd(__lhs).count() + __cd(__rhs).count());
653	}
654
655	/// The difference between two durations.
656	template<typename _Rep1, typename _Period1,
657	typename _Rep2, typename _Period2>
658	constexpr typename common_type<duration<_Rep1, _Period1>,
659	duration<_Rep2, _Period2>>::type
660	operator-(const duration<_Rep1, _Period1>& __lhs,
661	const duration<_Rep2, _Period2>& __rhs)
662	{
663	typedef duration<_Rep1, _Period1> __dur1;
664	typedef duration<_Rep2, _Period2> __dur2;
665	typedef typename common_type<__dur1,__dur2>::type __cd;
666	return __cd(__cd(__lhs).count() - __cd(__rhs).count());
667	}
668
669	/// @}
670
671	/// @cond undocumented
672
673	// SFINAE helper to obtain common_type<_Rep1, _Rep2> only if _Rep2
674	// is implicitly convertible to it.
675	// _GLIBCXX_RESOLVE_LIB_DEFECTS
676	// 3050. Conversion specification problem in chrono::duration constructor
677	template<typename _Rep1, typename _Rep2,
678	typename _CRep = typename common_type<_Rep1, _Rep2>::type>
679	using __common_rep_t = typename
680	enable_if<is_convertible<const _Rep2&, _CRep>::value, _CRep>::type;
681
682	/// @endcond
683
684	/** @{
685	* Arithmetic operators for chrono::duration
686	* @relates std::chrono::duration
687	*/
688
689	template<typename _Rep1, typename _Period, typename _Rep2>
690	constexpr duration<__common_rep_t<_Rep1, _Rep2>, _Period>
691	operator*(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
692	{
693	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
694	__cd;
695	return __cd(__cd(__d).count() * __s);
696	}
697
698	template<typename _Rep1, typename _Rep2, typename _Period>
699	constexpr duration<__common_rep_t<_Rep2, _Rep1>, _Period>
700	operator*(const _Rep1& __s, const duration<_Rep2, _Period>& __d)
701	{ return __d * __s; }
702
703	template<typename _Rep1, typename _Period, typename _Rep2>
704	constexpr
705	duration<__common_rep_t<_Rep1, __disable_if_is_duration<_Rep2>>, _Period>
706	operator/(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
707	{
708	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
709	__cd;
710	return __cd(__cd(__d).count() / __s);
711	}
712
713	template<typename _Rep1, typename _Period1,
714	typename _Rep2, typename _Period2>
715	constexpr typename common_type<_Rep1, _Rep2>::type
716	operator/(const duration<_Rep1, _Period1>& __lhs,
717	const duration<_Rep2, _Period2>& __rhs)
718	{
719	typedef duration<_Rep1, _Period1> __dur1;
720	typedef duration<_Rep2, _Period2> __dur2;
721	typedef typename common_type<__dur1,__dur2>::type __cd;
722	return __cd(__lhs).count() / __cd(__rhs).count();
723	}
724
725	// DR 934.
726	template<typename _Rep1, typename _Period, typename _Rep2>
727	constexpr
728	duration<__common_rep_t<_Rep1, __disable_if_is_duration<_Rep2>>, _Period>
729	operator%(const duration<_Rep1, _Period>& __d, const _Rep2& __s)
730	{
731	typedef duration<typename common_type<_Rep1, _Rep2>::type, _Period>
732	__cd;
733	return __cd(__cd(__d).count() % __s);
734	}
735
736	template<typename _Rep1, typename _Period1,
737	typename _Rep2, typename _Period2>
738	constexpr typename common_type<duration<_Rep1, _Period1>,
739	duration<_Rep2, _Period2>>::type
740	operator%(const duration<_Rep1, _Period1>& __lhs,
741	const duration<_Rep2, _Period2>& __rhs)
742	{
743	typedef duration<_Rep1, _Period1> __dur1;
744	typedef duration<_Rep2, _Period2> __dur2;
745	typedef typename common_type<__dur1,__dur2>::type __cd;
746	return __cd(__cd(__lhs).count() % __cd(__rhs).count());
747	}
748	/// @}
749
750	// comparisons
751
752	/** @{
753	* Comparisons for chrono::duration
754	* @relates std::chrono::duration
755	*/
756
757	template<typename _Rep1, typename _Period1,
758	typename _Rep2, typename _Period2>
759	constexpr bool
760	operator==(const duration<_Rep1, _Period1>& __lhs,
761	const duration<_Rep2, _Period2>& __rhs)
762	{
763	typedef duration<_Rep1, _Period1> __dur1;
764	typedef duration<_Rep2, _Period2> __dur2;
765	typedef typename common_type<__dur1,__dur2>::type __ct;
766	return __ct(__lhs).count() == __ct(__rhs).count();
767	}
768
769	template<typename _Rep1, typename _Period1,
770	typename _Rep2, typename _Period2>
771	constexpr bool
772	operator<(const duration<_Rep1, _Period1>& __lhs,
773	const duration<_Rep2, _Period2>& __rhs)
774	{
775	typedef duration<_Rep1, _Period1> __dur1;
776	typedef duration<_Rep2, _Period2> __dur2;
777	typedef typename common_type<__dur1,__dur2>::type __ct;
778	return __ct(__lhs).count() < __ct(__rhs).count();
779	}
780
781	#if __cpp_lib_three_way_comparison
782	template<typename _Rep1, typename _Period1,
783	typename _Rep2, typename _Period2>
784	requires three_way_comparable<common_type_t<_Rep1, _Rep2>>
785	constexpr auto
786	operator<=>(const duration<_Rep1, _Period1>& __lhs,
787	const duration<_Rep2, _Period2>& __rhs)
788	{
789	using __ct = common_type_t<duration<_Rep1, _Period1>,
790	duration<_Rep2, _Period2>>;
791	return __ct(__lhs).count() <=> __ct(__rhs).count();
792	}
793	#else
794	template<typename _Rep1, typename _Period1,
795	typename _Rep2, typename _Period2>
796	constexpr bool
797	operator!=(const duration<_Rep1, _Period1>& __lhs,
798	const duration<_Rep2, _Period2>& __rhs)
799	{ return !(__lhs == __rhs); }
800	#endif
801
802	template<typename _Rep1, typename _Period1,
803	typename _Rep2, typename _Period2>
804	constexpr bool
805	operator<=(const duration<_Rep1, _Period1>& __lhs,
806	const duration<_Rep2, _Period2>& __rhs)
807	{ return !(__rhs < __lhs); }
808
809	template<typename _Rep1, typename _Period1,
810	typename _Rep2, typename _Period2>
811	constexpr bool
812	operator>(const duration<_Rep1, _Period1>& __lhs,
813	const duration<_Rep2, _Period2>& __rhs)
814	{ return __rhs < __lhs; }
815
816	template<typename _Rep1, typename _Period1,
817	typename _Rep2, typename _Period2>
818	constexpr bool
819	operator>=(const duration<_Rep1, _Period1>& __lhs,
820	const duration<_Rep2, _Period2>& __rhs)
821	{ return !(__lhs < __rhs); }
822
823	/// @}
824
825	/// @cond undocumented
826	#ifdef _GLIBCXX_USE_C99_STDINT_TR1
827	# define _GLIBCXX_CHRONO_INT64_T int64_t
828	#elif defined __INT64_TYPE__
829	# define _GLIBCXX_CHRONO_INT64_T __INT64_TYPE__
830	#else
831	static_assert(std::numeric_limits<unsigned long long>::digits >= 64,
832	"Representation type for nanoseconds must have at least 64 bits");
833	# define _GLIBCXX_CHRONO_INT64_T long long
834	#endif
835	/// @endcond
836
837	/// nanoseconds
838	using nanoseconds = duration<_GLIBCXX_CHRONO_INT64_T, nano>;
839
840	/// microseconds
841	using microseconds = duration<_GLIBCXX_CHRONO_INT64_T, micro>;
842
843	/// milliseconds
844	using milliseconds = duration<_GLIBCXX_CHRONO_INT64_T, milli>;
845
846	/// seconds
847	using seconds = duration<_GLIBCXX_CHRONO_INT64_T>;
848
849	/// minutes
850	using minutes = duration<_GLIBCXX_CHRONO_INT64_T, ratio< 60>>;
851
852	/// hours
853	using hours = duration<_GLIBCXX_CHRONO_INT64_T, ratio<3600>>;
854
855	#if __cplusplus > 201703L
856	/// days
857	using days = duration<_GLIBCXX_CHRONO_INT64_T, ratio<86400>>;
858
859	/// weeks
860	using weeks = duration<_GLIBCXX_CHRONO_INT64_T, ratio<604800>>;
861
862	/// years
863	using years = duration<_GLIBCXX_CHRONO_INT64_T, ratio<31556952>>;
864
865	/// months
866	using months = duration<_GLIBCXX_CHRONO_INT64_T, ratio<2629746>>;
867	#endif // C++20
868
869	#undef _GLIBCXX_CHRONO_INT64_T
870
871	template<typename _Clock, typename _Dur>
872	struct time_point
873	{
874	static_assert(__is_duration<_Dur>::value,
875	"duration must be a specialization of std::chrono::duration");
876
877	typedef _Clock clock;
878	typedef _Dur duration;
879	typedef typename duration::rep rep;
880	typedef typename duration::period period;
881
882	constexpr time_point() : __d(duration::zero())
883	{ }
884
885	constexpr explicit time_point(const duration& __dur)
886	: __d(__dur)
887	{ }
888
889	// conversions
890	template<typename _Dur2,
891	typename = _Require<is_convertible<_Dur2, _Dur>>>
892	constexpr time_point(const time_point<clock, _Dur2>& __t)
893	: __d(__t.time_since_epoch())
894	{ }
895
896	// observer
897	constexpr duration
898	time_since_epoch() const
899	{ return __d; }
900
901	#if __cplusplus > 201703L
902	constexpr time_point&
903	operator++()
904	{
905	++__d;
906	return *this;
907	}
908
909	constexpr time_point
910	operator++(int)
911	{ return time_point{__d++}; }
912
913	constexpr time_point&
914	operator--()
915	{
916	--__d;
917	return *this;
918	}
919
920	constexpr time_point
921	operator--(int)
922	{ return time_point{__d--}; }
923	#endif
924
925	// arithmetic
926	_GLIBCXX17_CONSTEXPR time_point&
927	operator+=(const duration& __dur)
928	{
929	__d += __dur;
930	return *this;
931	}
932
933	_GLIBCXX17_CONSTEXPR time_point&
934	operator-=(const duration& __dur)
935	{
936	__d -= __dur;
937	return *this;
938	}
939
940	// special values
941	static constexpr time_point
942	min() noexcept
943	{ return time_point(duration::min()); }
944
945	static constexpr time_point
946	max() noexcept
947	{ return time_point(duration::max()); }
948
949	private:
950	duration __d;
951	};
952
953	/// time_point_cast
954	template<typename _ToDur, typename _Clock, typename _Dur>
955	constexpr typename enable_if<__is_duration<_ToDur>::value,
956	time_point<_Clock, _ToDur>>::type
957	time_point_cast(const time_point<_Clock, _Dur>& __t)
958	{
959	typedef time_point<_Clock, _ToDur> __time_point;
960	return __time_point(duration_cast<_ToDur>(__t.time_since_epoch()));
961	}
962
963	#if __cplusplus > 201402L
964	template<typename _ToDur, typename _Clock, typename _Dur>
965	constexpr
966	enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
967	floor(const time_point<_Clock, _Dur>& __tp)
968	{
969	return time_point<_Clock, _ToDur>{
970	chrono::floor<_ToDur>(__tp.time_since_epoch())};
971	}
972
973	template<typename _ToDur, typename _Clock, typename _Dur>
974	constexpr
975	enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
976	ceil(const time_point<_Clock, _Dur>& __tp)
977	{
978	return time_point<_Clock, _ToDur>{
979	chrono::ceil<_ToDur>(__tp.time_since_epoch())};
980	}
981
982	template<typename _ToDur, typename _Clock, typename _Dur>
983	constexpr enable_if_t<
984	__and_<__is_duration<_ToDur>,
985	__not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
986	time_point<_Clock, _ToDur>>
987	round(const time_point<_Clock, _Dur>& __tp)
988	{
989	return time_point<_Clock, _ToDur>{
990	chrono::round<_ToDur>(__tp.time_since_epoch())};
991	}
992	#endif // C++17
993
994	/// @{
995	/// @relates time_point
996
997	/// Adjust a time point forwards by the given duration.
998	template<typename _Clock, typename _Dur1,
999	typename _Rep2, typename _Period2>
1000	constexpr time_point<_Clock,
1001	typename common_type<_Dur1, duration<_Rep2, _Period2>>::type>
1002	operator+(const time_point<_Clock, _Dur1>& __lhs,
1003	const duration<_Rep2, _Period2>& __rhs)
1004	{
1005	typedef duration<_Rep2, _Period2> __dur2;
1006	typedef typename common_type<_Dur1,__dur2>::type __ct;
1007	typedef time_point<_Clock, __ct> __time_point;
1008	return __time_point(__lhs.time_since_epoch() + __rhs);
1009	}
1010
1011	/// Adjust a time point forwards by the given duration.
1012	template<typename _Rep1, typename _Period1,
1013	typename _Clock, typename _Dur2>
1014	constexpr time_point<_Clock,
1015	typename common_type<duration<_Rep1, _Period1>, _Dur2>::type>
1016	operator+(const duration<_Rep1, _Period1>& __lhs,
1017	const time_point<_Clock, _Dur2>& __rhs)
1018	{
1019	typedef duration<_Rep1, _Period1> __dur1;
1020	typedef typename common_type<__dur1,_Dur2>::type __ct;
1021	typedef time_point<_Clock, __ct> __time_point;
1022	return __time_point(__rhs.time_since_epoch() + __lhs);
1023	}
1024
1025	/// Adjust a time point backwards by the given duration.
1026	template<typename _Clock, typename _Dur1,
1027	typename _Rep2, typename _Period2>
1028	constexpr time_point<_Clock,
1029	typename common_type<_Dur1, duration<_Rep2, _Period2>>::type>
1030	operator-(const time_point<_Clock, _Dur1>& __lhs,
1031	const duration<_Rep2, _Period2>& __rhs)
1032	{
1033	typedef duration<_Rep2, _Period2> __dur2;
1034	typedef typename common_type<_Dur1,__dur2>::type __ct;
1035	typedef time_point<_Clock, __ct> __time_point;
1036	return __time_point(__lhs.time_since_epoch() -__rhs);
1037	}
1038
1039	/// The difference between two time points (as a duration)
1040	template<typename _Clock, typename _Dur1, typename _Dur2>
1041	constexpr typename common_type<_Dur1, _Dur2>::type
1042	operator-(const time_point<_Clock, _Dur1>& __lhs,
1043	const time_point<_Clock, _Dur2>& __rhs)
1044	{ return __lhs.time_since_epoch() - __rhs.time_since_epoch(); }
1045	/// @}
1046
1047	/** @{
1048	* Comparisons for time_point
1049	* @relates chrono::time_point
1050	*/
1051
1052	template<typename _Clock, typename _Dur1, typename _Dur2>
1053	constexpr bool
1054	operator==(const time_point<_Clock, _Dur1>& __lhs,
1055	const time_point<_Clock, _Dur2>& __rhs)
1056	{ return __lhs.time_since_epoch() == __rhs.time_since_epoch(); }
1057
1058	#if __cpp_lib_three_way_comparison
1059	template<typename _Clock, typename _Dur1,
1060	three_way_comparable_with<_Dur1> _Dur2>
1061	constexpr auto
1062	operator<=>(const time_point<_Clock, _Dur1>& __lhs,
1063	const time_point<_Clock, _Dur2>& __rhs)
1064	{ return __lhs.time_since_epoch() <=> __rhs.time_since_epoch(); }
1065	#else
1066	template<typename _Clock, typename _Dur1, typename _Dur2>
1067	constexpr bool
1068	operator!=(const time_point<_Clock, _Dur1>& __lhs,
1069	const time_point<_Clock, _Dur2>& __rhs)
1070	{ return !(__lhs == __rhs); }
1071	#endif
1072
1073	template<typename _Clock, typename _Dur1, typename _Dur2>
1074	constexpr bool
1075	operator<(const time_point<_Clock, _Dur1>& __lhs,
1076	const time_point<_Clock, _Dur2>& __rhs)
1077	{ return __lhs.time_since_epoch() < __rhs.time_since_epoch(); }
1078
1079	template<typename _Clock, typename _Dur1, typename _Dur2>
1080	constexpr bool
1081	operator<=(const time_point<_Clock, _Dur1>& __lhs,
1082	const time_point<_Clock, _Dur2>& __rhs)
1083	{ return !(__rhs < __lhs); }
1084
1085	template<typename _Clock, typename _Dur1, typename _Dur2>
1086	constexpr bool
1087	operator>(const time_point<_Clock, _Dur1>& __lhs,
1088	const time_point<_Clock, _Dur2>& __rhs)
1089	{ return __rhs < __lhs; }
1090
1091	template<typename _Clock, typename _Dur1, typename _Dur2>
1092	constexpr bool
1093	operator>=(const time_point<_Clock, _Dur1>& __lhs,
1094	const time_point<_Clock, _Dur2>& __rhs)
1095	{ return !(__lhs < __rhs); }
1096
1097	/// @}
1098
1099	// Clocks.
1100
1101	// Why nanosecond resolution as the default?
1102	// Why have std::system_clock always count in the highest
1103	// resolution (ie nanoseconds), even if on some OSes the low 3
1104	// or 9 decimal digits will be always zero? This allows later
1105	// implementations to change the system_clock::now()
1106	// implementation any time to provide better resolution without
1107	// changing function signature or units.
1108
1109	// To support the (forward) evolution of the library's defined
1110	// clocks, wrap inside inline namespace so that the current
1111	// defintions of system_clock, steady_clock, and
1112	// high_resolution_clock types are uniquely mangled. This way, new
1113	// code can use the latests clocks, while the library can contain
1114	// compatibility definitions for previous versions. At some
1115	// point, when these clocks settle down, the inlined namespaces
1116	// can be removed. XXX GLIBCXX_ABI Deprecated
1117	inline namespace _V2 {
1118
1119	/**
1120	* @brief System clock.
1121	*
1122	* Time returned represents wall time from the system-wide clock.
1123	* @ingroup chrono
1124	*/
1125	struct system_clock
1126	{
1127	typedef chrono::nanoseconds duration;
1128	typedef duration::rep rep;
1129	typedef duration::period period;
1130	typedef chrono::time_point<system_clock, duration> time_point;
1131
1132	static_assert(system_clock::duration::min()
1133	< system_clock::duration::zero(),
1134	"a clock's minimum duration cannot be less than its epoch");
1135
1136	static constexpr bool is_steady = false;
1137
1138	static time_point
1139	now() noexcept;
1140
1141	// Map to C API
1142	static std::time_t
1143	to_time_t(const time_point& __t) noexcept
1144	{
1145	return std::time_t(duration_cast<chrono::seconds>
1146	(d: __t.time_since_epoch()).count());
1147	}
1148
1149	static time_point
1150	from_time_t(std::time_t __t) noexcept
1151	{
1152	typedef chrono::time_point<system_clock, seconds> __from;
1153	return time_point_cast<system_clock::duration>
1154	(t: __from(chrono::seconds(__t)));
1155	}
1156	};
1157
1158
1159	/**
1160	* @brief Monotonic clock
1161	*
1162	* Time returned has the property of only increasing at a uniform rate.
1163	* @ingroup chrono
1164	*/
1165	struct steady_clock
1166	{
1167	typedef chrono::nanoseconds duration;
1168	typedef duration::rep rep;
1169	typedef duration::period period;
1170	typedef chrono::time_point<steady_clock, duration> time_point;
1171
1172	static constexpr bool is_steady = true;
1173
1174	static time_point
1175	now() noexcept;
1176	};
1177
1178
1179	/**
1180	* @brief Highest-resolution clock
1181	*
1182	* This is the clock "with the shortest tick period." Alias to
1183	* std::system_clock until higher-than-nanosecond definitions
1184	* become feasible.
1185	* @ingroup chrono
1186	*/
1187	using high_resolution_clock = system_clock;
1188
1189	} // end inline namespace _V2
1190
1191	#if __cplusplus > 201703L
1192	template<typename _Duration>
1193	using sys_time = time_point<system_clock, _Duration>;
1194	using sys_seconds = sys_time<seconds>;
1195	using sys_days = sys_time<days>;
1196
1197	using file_clock = ::std::filesystem::__file_clock;
1198
1199	template<typename _Duration>
1200	using file_time = time_point<file_clock, _Duration>;
1201
1202	template<> struct is_clock<system_clock> : true_type { };
1203	template<> struct is_clock<steady_clock> : true_type { };
1204	template<> struct is_clock<file_clock> : true_type { };
1205
1206	template<> inline constexpr bool is_clock_v<system_clock> = true;
1207	template<> inline constexpr bool is_clock_v<steady_clock> = true;
1208	template<> inline constexpr bool is_clock_v<file_clock> = true;
1209
1210	struct local_t { };
1211	template<typename _Duration>
1212	using local_time = time_point<local_t, _Duration>;
1213	using local_seconds = local_time<seconds>;
1214	using local_days = local_time<days>;
1215
1216	class utc_clock;
1217	class tai_clock;
1218	class gps_clock;
1219
1220	template<typename _Duration>
1221	using utc_time = time_point<utc_clock, _Duration>;
1222	using utc_seconds = utc_time<seconds>;
1223
1224	template<typename _Duration>
1225	using tai_time = time_point<tai_clock, _Duration>;
1226	using tai_seconds = tai_time<seconds>;
1227
1228	template<typename _Duration>
1229	using gps_time = time_point<gps_clock, _Duration>;
1230	using gps_seconds = gps_time<seconds>;
1231
1232	template<> struct is_clock<utc_clock> : true_type { };
1233	template<> struct is_clock<tai_clock> : true_type { };
1234	template<> struct is_clock<gps_clock> : true_type { };
1235
1236	template<> inline constexpr bool is_clock_v<utc_clock> = true;
1237	template<> inline constexpr bool is_clock_v<tai_clock> = true;
1238	template<> inline constexpr bool is_clock_v<gps_clock> = true;
1239
1240	struct leap_second_info
1241	{
1242	bool is_leap_second;
1243	seconds elapsed;
1244	};
1245
1246	// CALENDRICAL TYPES
1247
1248	// CLASS DECLARATIONS
1249	class day;
1250	class month;
1251	class year;
1252	class weekday;
1253	class weekday_indexed;
1254	class weekday_last;
1255	class month_day;
1256	class month_day_last;
1257	class month_weekday;
1258	class month_weekday_last;
1259	class year_month;
1260	class year_month_day;
1261	class year_month_day_last;
1262	class year_month_weekday;
1263	class year_month_weekday_last;
1264
1265	struct last_spec
1266	{
1267	explicit last_spec() = default;
1268
1269	friend constexpr month_day_last
1270	operator/(int __m, last_spec) noexcept;
1271
1272	friend constexpr month_day_last
1273	operator/(last_spec, int __m) noexcept;
1274	};
1275
1276	inline constexpr last_spec last{};
1277
1278	namespace __detail
1279	{
1280	// Compute the remainder of the Euclidean division of __n divided by __d.
1281	// Euclidean division truncates toward negative infinity and always
1282	// produces a remainder in the range of [0,__d-1] (whereas standard
1283	// division truncates toward zero and yields a nonpositive remainder
1284	// for negative __n).
1285	constexpr unsigned
1286	__modulo(long long __n, unsigned __d)
1287	{
1288	if (__n >= 0)
1289	return __n % __d;
1290	else
1291	return (__d + (__n % __d)) % __d;
1292	}
1293
1294	inline constexpr unsigned __days_per_month[12]
1295	= { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
1296	}
1297
1298	// DAY
1299
1300	class day
1301	{
1302	private:
1303	unsigned char _M_d;
1304
1305	public:
1306	day() = default;
1307
1308	explicit constexpr
1309	day(unsigned __d) noexcept
1310	: _M_d(__d)
1311	{ }
1312
1313	constexpr day&
1314	operator++() noexcept
1315	{
1316	++_M_d;
1317	return *this;
1318	}
1319
1320	constexpr day
1321	operator++(int) noexcept
1322	{
1323	auto __ret = *this;
1324	++(*this);
1325	return __ret;
1326	}
1327
1328	constexpr day&
1329	operator--() noexcept
1330	{
1331	--_M_d;
1332	return *this;
1333	}
1334
1335	constexpr day
1336	operator--(int) noexcept
1337	{
1338	auto __ret = *this;
1339	--(*this);
1340	return __ret;
1341	}
1342
1343	constexpr day&
1344	operator+=(const days& __d) noexcept
1345	{
1346	*this = *this + __d;
1347	return *this;
1348	}
1349
1350	constexpr day&
1351	operator-=(const days& __d) noexcept
1352	{
1353	*this = *this - __d;
1354	return *this;
1355	}
1356
1357	constexpr explicit
1358	operator unsigned() const noexcept
1359	{ return _M_d; }
1360
1361	constexpr bool
1362	ok() const noexcept
1363	{ return 1 <= _M_d && _M_d <= 31; }
1364
1365	friend constexpr bool
1366	operator==(const day& __x, const day& __y) noexcept
1367	{ return unsigned{__x} == unsigned{__y}; }
1368
1369	friend constexpr strong_ordering
1370	operator<=>(const day& __x, const day& __y) noexcept
1371	{ return unsigned{__x} <=> unsigned{__y}; }
1372
1373	friend constexpr day
1374	operator+(const day& __x, const days& __y) noexcept
1375	{ return day(unsigned{__x} + __y.count()); }
1376
1377	friend constexpr day
1378	operator+(const days& __x, const day& __y) noexcept
1379	{ return __y + __x; }
1380
1381	friend constexpr day
1382	operator-(const day& __x, const days& __y) noexcept
1383	{ return __x + -__y; }
1384
1385	friend constexpr days
1386	operator-(const day& __x, const day& __y) noexcept
1387	{ return days{int(unsigned{__x}) - int(unsigned{__y})}; }
1388
1389	friend constexpr month_day
1390	operator/(const month& __m, const day& __d) noexcept;
1391
1392	friend constexpr month_day
1393	operator/(int __m, const day& __d) noexcept;
1394
1395	friend constexpr month_day
1396	operator/(const day& __d, const month& __m) noexcept;
1397
1398	friend constexpr month_day
1399	operator/(const day& __d, int __m) noexcept;
1400
1401	friend constexpr year_month_day
1402	operator/(const year_month& __ym, const day& __d) noexcept;
1403
1404	// TODO: Implement operator<<, to_stream, from_stream.
1405	};
1406
1407	// MONTH
1408
1409	class month
1410	{
1411	private:
1412	unsigned char _M_m;
1413
1414	public:
1415	month() = default;
1416
1417	explicit constexpr
1418	month(unsigned __m) noexcept
1419	: _M_m(__m)
1420	{ }
1421
1422	constexpr month&
1423	operator++() noexcept
1424	{
1425	*this += months{1};
1426	return *this;
1427	}
1428
1429	constexpr month
1430	operator++(int) noexcept
1431	{
1432	auto __ret = *this;
1433	++(*this);
1434	return __ret;
1435	}
1436
1437	constexpr month&
1438	operator--() noexcept
1439	{
1440	*this -= months{1};
1441	return *this;
1442	}
1443
1444	constexpr month
1445	operator--(int) noexcept
1446	{
1447	auto __ret = *this;
1448	--(*this);
1449	return __ret;
1450	}
1451
1452	constexpr month&
1453	operator+=(const months& __m) noexcept
1454	{
1455	*this = *this + __m;
1456	return *this;
1457	}
1458
1459	constexpr month&
1460	operator-=(const months& __m) noexcept
1461	{
1462	*this = *this - __m;
1463	return *this;
1464	}
1465
1466	explicit constexpr
1467	operator unsigned() const noexcept
1468	{ return _M_m; }
1469
1470	constexpr bool
1471	ok() const noexcept
1472	{ return 1 <= _M_m && _M_m <= 12; }
1473
1474	friend constexpr bool
1475	operator==(const month& __x, const month& __y) noexcept
1476	{ return unsigned{__x} == unsigned{__y}; }
1477
1478	friend constexpr strong_ordering
1479	operator<=>(const month& __x, const month& __y) noexcept
1480	{ return unsigned{__x} <=> unsigned{__y}; }
1481
1482	friend constexpr month
1483	operator+(const month& __x, const months& __y) noexcept
1484	{
1485	auto __n = static_cast<long long>(unsigned{__x}) + (__y.count() - 1);
1486	return month{__detail::__modulo(__n, d: 12) + 1};
1487	}
1488
1489	friend constexpr month
1490	operator+(const months& __x, const month& __y) noexcept
1491	{ return __y + __x; }
1492
1493	friend constexpr month
1494	operator-(const month& __x, const months& __y) noexcept
1495	{ return __x + -__y; }
1496
1497	friend constexpr months
1498	operator-(const month& __x, const month& __y) noexcept
1499	{
1500	const auto __dm = int(unsigned(__x)) - int(unsigned(__y));
1501	return months{__dm < 0 ? 12 + __dm : __dm};
1502	}
1503
1504	friend constexpr year_month
1505	operator/(const year& __y, const month& __m) noexcept;
1506
1507	friend constexpr month_day
1508	operator/(const month& __m, int __d) noexcept;
1509
1510	friend constexpr month_day_last
1511	operator/(const month& __m, last_spec) noexcept;
1512
1513	friend constexpr month_day_last
1514	operator/(last_spec, const month& __m) noexcept;
1515
1516	friend constexpr month_weekday
1517	operator/(const month& __m, const weekday_indexed& __wdi) noexcept;
1518
1519	friend constexpr month_weekday
1520	operator/(const weekday_indexed& __wdi, const month& __m) noexcept;
1521
1522	friend constexpr month_weekday_last
1523	operator/(const month& __m, const weekday_last& __wdl) noexcept;
1524
1525	friend constexpr month_weekday_last
1526	operator/(const weekday_last& __wdl, const month& __m) noexcept;
1527
1528	// TODO: Implement operator<<, to_stream, from_stream.
1529	};
1530
1531	inline constexpr month January{1};
1532	inline constexpr month February{2};
1533	inline constexpr month March{3};
1534	inline constexpr month April{4};
1535	inline constexpr month May{5};
1536	inline constexpr month June{6};
1537	inline constexpr month July{7};
1538	inline constexpr month August{8};
1539	inline constexpr month September{9};
1540	inline constexpr month October{10};
1541	inline constexpr month November{11};
1542	inline constexpr month December{12};
1543
1544	// YEAR
1545
1546	class year
1547	{
1548	private:
1549	short _M_y;
1550
1551	public:
1552	year() = default;
1553
1554	explicit constexpr
1555	year(int __y) noexcept
1556	: _M_y{static_cast<short>(__y)}
1557	{ }
1558
1559	static constexpr year
1560	min() noexcept
1561	{ return year{-32767}; }
1562
1563	static constexpr year
1564	max() noexcept
1565	{ return year{32767}; }
1566
1567	constexpr year&
1568	operator++() noexcept
1569	{
1570	++_M_y;
1571	return *this;
1572	}
1573
1574	constexpr year
1575	operator++(int) noexcept
1576	{
1577	auto __ret = *this;
1578	++(*this);
1579	return __ret;
1580	}
1581
1582	constexpr year&
1583	operator--() noexcept
1584	{
1585	--_M_y;
1586	return *this;
1587	}
1588
1589	constexpr year
1590	operator--(int) noexcept
1591	{
1592	auto __ret = *this;
1593	--(*this);
1594	return __ret;
1595	}
1596
1597	constexpr year&
1598	operator+=(const years& __y) noexcept
1599	{
1600	*this = *this + __y;
1601	return *this;
1602	}
1603
1604	constexpr year&
1605	operator-=(const years& __y) noexcept
1606	{
1607	*this = *this - __y;
1608	return *this;
1609	}
1610
1611	constexpr year
1612	operator+() const noexcept
1613	{ return *this; }
1614
1615	constexpr year
1616	operator-() const noexcept
1617	{ return year{-_M_y}; }
1618
1619	constexpr bool
1620	is_leap() const noexcept
1621	{
1622	// Testing divisibility by 100 first gives better performance, that is,
1623	// return (_M_y % 100 != 0 || _M_y % 400 == 0) && _M_y % 4 == 0;
1624
1625	// It gets even faster if _M_y is in [-536870800, 536870999]
1626	// (which is the case here) and _M_y % 100 is replaced by
1627	// __is_multiple_of_100 below.
1628
1629	// References:
1630	// [1] https://github.com/cassioneri/calendar
1631	// [2] https://accu.org/journals/overload/28/155/overload155.pdf#page=16
1632
1633	constexpr uint32_t __multiplier = 42949673;
1634	constexpr uint32_t __bound = 42949669;
1635	constexpr uint32_t __max_dividend = 1073741799;
1636	constexpr uint32_t __offset = __max_dividend / 2 / 100 * 100;
1637	const bool __is_multiple_of_100
1638	= __multiplier * (_M_y + __offset) < __bound;
1639	return (!__is_multiple_of_100 || _M_y % 400 == 0) && _M_y % 4 == 0;
1640	}
1641
1642	explicit constexpr
1643	operator int() const noexcept
1644	{ return _M_y; }
1645
1646	constexpr bool
1647	ok() const noexcept
1648	{ return min()._M_y <= _M_y && _M_y <= max()._M_y; }
1649
1650	friend constexpr bool
1651	operator==(const year& __x, const year& __y) noexcept
1652	{ return int{__x} == int{__y}; }
1653
1654	friend constexpr strong_ordering
1655	operator<=>(const year& __x, const year& __y) noexcept
1656	{ return int{__x} <=> int{__y}; }
1657
1658	friend constexpr year
1659	operator+(const year& __x, const years& __y) noexcept
1660	{ return year{int{__x} + static_cast<int>(__y.count())}; }
1661
1662	friend constexpr year
1663	operator+(const years& __x, const year& __y) noexcept
1664	{ return __y + __x; }
1665
1666	friend constexpr year
1667	operator-(const year& __x, const years& __y) noexcept
1668	{ return __x + -__y; }
1669
1670	friend constexpr years
1671	operator-(const year& __x, const year& __y) noexcept
1672	{ return years{int{__x} - int{__y}}; }
1673
1674	friend constexpr year_month
1675	operator/(const year& __y, int __m) noexcept;
1676
1677	friend constexpr year_month_day
1678	operator/(const year& __y, const month_day& __md) noexcept;
1679
1680	friend constexpr year_month_day
1681	operator/(const month_day& __md, const year& __y) noexcept;
1682
1683	friend constexpr year_month_day_last
1684	operator/(const year& __y, const month_day_last& __mdl) noexcept;
1685
1686	friend constexpr year_month_day_last
1687	operator/(const month_day_last& __mdl, const year& __y) noexcept;
1688
1689	friend constexpr year_month_weekday
1690	operator/(const year& __y, const month_weekday& __mwd) noexcept;
1691
1692	friend constexpr year_month_weekday
1693	operator/(const month_weekday& __mwd, const year& __y) noexcept;
1694
1695	friend constexpr year_month_weekday_last
1696	operator/(const year& __y, const month_weekday_last& __mwdl) noexcept;
1697
1698	friend constexpr year_month_weekday_last
1699	operator/(const month_weekday_last& __mwdl, const year& __y) noexcept;
1700
1701	// TODO: Implement operator<<, to_stream, from_stream.
1702	};
1703
1704	// WEEKDAY
1705
1706	class weekday
1707	{
1708	private:
1709	unsigned char _M_wd;
1710
1711	static constexpr weekday
1712	_S_from_days(const days& __d)
1713	{
1714	auto __n = __d.count();
1715	return weekday(__n >= -4 ? (__n + 4) % 7 : (__n + 5) % 7 + 6);
1716	}
1717
1718	public:
1719	weekday() = default;
1720
1721	explicit constexpr
1722	weekday(unsigned __wd) noexcept
1723	: _M_wd(__wd == 7 ? 0 : __wd) // __wd % 7 ?
1724	{ }
1725
1726	constexpr
1727	weekday(const sys_days& __dp) noexcept
1728	: weekday{_S_from_days(d: __dp.time_since_epoch())}
1729	{ }
1730
1731	explicit constexpr
1732	weekday(const local_days& __dp) noexcept
1733	: weekday{sys_days{__dp.time_since_epoch()}}
1734	{ }
1735
1736	constexpr weekday&
1737	operator++() noexcept
1738	{
1739	*this += days{1};
1740	return *this;
1741	}
1742
1743	constexpr weekday
1744	operator++(int) noexcept
1745	{
1746	auto __ret = *this;
1747	++(*this);
1748	return __ret;
1749	}
1750
1751	constexpr weekday&
1752	operator--() noexcept
1753	{
1754	*this -= days{1};
1755	return *this;
1756	}
1757
1758	constexpr weekday
1759	operator--(int) noexcept
1760	{
1761	auto __ret = *this;
1762	--(*this);
1763	return __ret;
1764	}
1765
1766	constexpr weekday&
1767	operator+=(const days& __d) noexcept
1768	{
1769	*this = *this + __d;
1770	return *this;
1771	}
1772
1773	constexpr weekday&
1774	operator-=(const days& __d) noexcept
1775	{
1776	*this = *this - __d;
1777	return *this;
1778	}
1779
1780	constexpr unsigned
1781	c_encoding() const noexcept
1782	{ return _M_wd; }
1783
1784	constexpr unsigned
1785	iso_encoding() const noexcept
1786	{ return _M_wd == 0u ? 7u : _M_wd; }
1787
1788	constexpr bool
1789	ok() const noexcept
1790	{ return _M_wd <= 6; }
1791
1792	constexpr weekday_indexed
1793	operator[](unsigned __index) const noexcept;
1794
1795	constexpr weekday_last
1796	operator[](last_spec) const noexcept;
1797
1798	friend constexpr bool
1799	operator==(const weekday& __x, const weekday& __y) noexcept
1800	{ return __x._M_wd == __y._M_wd; }
1801
1802	friend constexpr weekday
1803	operator+(const weekday& __x, const days& __y) noexcept
1804	{
1805	auto __n = static_cast<long long>(__x._M_wd) + __y.count();
1806	return weekday{__detail::__modulo(__n, d: 7)};
1807	}
1808
1809	friend constexpr weekday
1810	operator+(const days& __x, const weekday& __y) noexcept
1811	{ return __y + __x; }
1812
1813	friend constexpr weekday
1814	operator-(const weekday& __x, const days& __y) noexcept
1815	{ return __x + -__y; }
1816
1817	friend constexpr days
1818	operator-(const weekday& __x, const weekday& __y) noexcept
1819	{
1820	auto __n = static_cast<long long>(__x._M_wd) - __y._M_wd;
1821	return days{__detail::__modulo(__n, d: 7)};
1822	}
1823
1824	// TODO: operator<<, from_stream.
1825	};
1826
1827	inline constexpr weekday Sunday{0};
1828	inline constexpr weekday Monday{1};
1829	inline constexpr weekday Tuesday{2};
1830	inline constexpr weekday Wednesday{3};
1831	inline constexpr weekday Thursday{4};
1832	inline constexpr weekday Friday{5};
1833	inline constexpr weekday Saturday{6};
1834
1835	// WEEKDAY_INDEXED
1836
1837	class weekday_indexed
1838	{
1839	private:
1840	chrono::weekday _M_wd;
1841	unsigned char _M_index;
1842
1843	public:
1844	weekday_indexed() = default;
1845
1846	constexpr
1847	weekday_indexed(const chrono::weekday& __wd, unsigned __index) noexcept
1848	: _M_wd(__wd), _M_index(__index)
1849	{ }
1850
1851	constexpr chrono::weekday
1852	weekday() const noexcept
1853	{ return _M_wd; }
1854
1855	constexpr unsigned
1856	index() const noexcept
1857	{ return _M_index; };
1858
1859	constexpr bool
1860	ok() const noexcept
1861	{ return _M_wd.ok() && 1 <= _M_index && _M_index <= 5; }
1862
1863	friend constexpr bool
1864	operator==(const weekday_indexed& __x, const weekday_indexed& __y) noexcept
1865	{ return __x.weekday() == __y.weekday() && __x.index() == __y.index(); }
1866
1867	friend constexpr month_weekday
1868	operator/(const month& __m, const weekday_indexed& __wdi) noexcept;
1869
1870	friend constexpr month_weekday
1871	operator/(int __m, const weekday_indexed& __wdi) noexcept;
1872
1873	friend constexpr month_weekday
1874	operator/(const weekday_indexed& __wdi, const month& __m) noexcept;
1875
1876	friend constexpr month_weekday
1877	operator/(const weekday_indexed& __wdi, int __m) noexcept;
1878
1879	friend constexpr year_month_weekday
1880	operator/(const year_month& __ym, const weekday_indexed& __wdi) noexcept;
1881
1882	// TODO: Implement operator<<.
1883	};
1884
1885	constexpr weekday_indexed
1886	weekday::operator[](unsigned __index) const noexcept
1887	{ return {*this, __index}; }
1888
1889	// WEEKDAY_LAST
1890
1891	class weekday_last
1892	{
1893	private:
1894	chrono::weekday _M_wd;
1895
1896	public:
1897	explicit constexpr
1898	weekday_last(const chrono::weekday& __wd) noexcept
1899	: _M_wd{__wd}
1900	{ }
1901
1902	constexpr chrono::weekday
1903	weekday() const noexcept
1904	{ return _M_wd; }
1905
1906	constexpr bool
1907	ok() const noexcept
1908	{ return _M_wd.ok(); }
1909
1910	friend constexpr bool
1911	operator==(const weekday_last& __x, const weekday_last& __y) noexcept
1912	{ return __x.weekday() == __y.weekday(); }
1913
1914	friend constexpr month_weekday_last
1915	operator/(int __m, const weekday_last& __wdl) noexcept;
1916
1917	friend constexpr month_weekday_last
1918	operator/(const weekday_last& __wdl, int __m) noexcept;
1919
1920	friend constexpr year_month_weekday_last
1921	operator/(const year_month& __ym, const weekday_last& __wdl) noexcept;
1922
1923	// TODO: Implement operator<<.
1924	};
1925
1926	constexpr weekday_last
1927	weekday::operator[](last_spec) const noexcept
1928	{ return weekday_last{*this}; }
1929
1930	// MONTH_DAY
1931
1932	class month_day
1933	{
1934	private:
1935	chrono::month _M_m;
1936	chrono::day _M_d;
1937
1938	public:
1939	month_day() = default;
1940
1941	constexpr
1942	month_day(const chrono::month& __m, const chrono::day& __d) noexcept
1943	: _M_m{__m}, _M_d{__d}
1944	{ }
1945
1946	constexpr chrono::month
1947	month() const noexcept
1948	{ return _M_m; }
1949
1950	constexpr chrono::day
1951	day() const noexcept
1952	{ return _M_d; }
1953
1954	constexpr bool
1955	ok() const noexcept
1956	{
1957	return _M_m.ok()
1958	&& 1u <= unsigned(_M_d)
1959	&& unsigned(_M_d) <= __detail::__days_per_month[unsigned(_M_m) - 1];
1960	}
1961
1962	friend constexpr bool
1963	operator==(const month_day& __x, const month_day& __y) noexcept
1964	{ return __x.month() == __y.month() && __x.day() == __y.day(); }
1965
1966	friend constexpr strong_ordering
1967	operator<=>(const month_day& __x, const month_day& __y) noexcept
1968	= default;
1969
1970	friend constexpr month_day
1971	operator/(const chrono::month& __m, const chrono::day& __d) noexcept
1972	{ return {__m, __d}; }
1973
1974	friend constexpr month_day
1975	operator/(const chrono::month& __m, int __d) noexcept
1976	{ return {__m, chrono::day(unsigned(__d))}; }
1977
1978	friend constexpr month_day
1979	operator/(int __m, const chrono::day& __d) noexcept
1980	{ return {chrono::month(unsigned(__m)), __d}; }
1981
1982	friend constexpr month_day
1983	operator/(const chrono::day& __d, const chrono::month& __m) noexcept
1984	{ return {__m, __d}; }
1985
1986	friend constexpr month_day
1987	operator/(const chrono::day& __d, int __m) noexcept
1988	{ return {chrono::month(unsigned(__m)), __d}; }
1989
1990	friend constexpr year_month_day
1991	operator/(int __y, const month_day& __md) noexcept;
1992
1993	friend constexpr year_month_day
1994	operator/(const month_day& __md, int __y) noexcept;
1995
1996	// TODO: Implement operator<<, from_stream.
1997	};
1998
1999	// MONTH_DAY_LAST
2000
2001	class month_day_last
2002	{
2003	private:
2004	chrono::month _M_m;
2005
2006	public:
2007	explicit constexpr
2008	month_day_last(const chrono::month& __m) noexcept
2009	: _M_m{__m}
2010	{ }
2011
2012	constexpr chrono::month
2013	month() const noexcept
2014	{ return _M_m; }
2015
2016	constexpr bool
2017	ok() const noexcept
2018	{ return _M_m.ok(); }
2019
2020	friend constexpr bool
2021	operator==(const month_day_last& __x, const month_day_last& __y) noexcept
2022	{ return __x.month() == __y.month(); }
2023
2024	friend constexpr strong_ordering
2025	operator<=>(const month_day_last& __x, const month_day_last& __y) noexcept
2026	= default;
2027
2028	friend constexpr month_day_last
2029	operator/(const chrono::month& __m, last_spec) noexcept
2030	{ return month_day_last{__m}; }
2031
2032	friend constexpr month_day_last
2033	operator/(int __m, last_spec) noexcept
2034	{ return chrono::month(unsigned(__m)) / last; }
2035
2036	friend constexpr month_day_last
2037	operator/(last_spec, const chrono::month& __m) noexcept
2038	{ return __m / last; }
2039
2040	friend constexpr month_day_last
2041	operator/(last_spec, int __m) noexcept
2042	{ return __m / last; }
2043
2044	friend constexpr year_month_day_last
2045	operator/(int __y, const month_day_last& __mdl) noexcept;
2046
2047	friend constexpr year_month_day_last
2048	operator/(const month_day_last& __mdl, int __y) noexcept;
2049
2050	// TODO: Implement operator<<.
2051	};
2052
2053	// MONTH_WEEKDAY
2054
2055	class month_weekday
2056	{
2057	private:
2058	chrono::month _M_m;
2059	chrono::weekday_indexed _M_wdi;
2060
2061	public:
2062	constexpr
2063	month_weekday(const chrono::month& __m,
2064	const chrono::weekday_indexed& __wdi) noexcept
2065	: _M_m{__m}, _M_wdi{__wdi}
2066	{ }
2067
2068	constexpr chrono::month
2069	month() const noexcept
2070	{ return _M_m; }
2071
2072	constexpr chrono::weekday_indexed
2073	weekday_indexed() const noexcept
2074	{ return _M_wdi; }
2075
2076	constexpr bool
2077	ok() const noexcept
2078	{ return _M_m.ok() && _M_wdi.ok(); }
2079
2080	friend constexpr bool
2081	operator==(const month_weekday& __x, const month_weekday& __y) noexcept
2082	{
2083	return __x.month() == __y.month()
2084	&& __x.weekday_indexed() == __y.weekday_indexed();
2085	}
2086
2087	friend constexpr month_weekday
2088	operator/(const chrono::month& __m,
2089	const chrono::weekday_indexed& __wdi) noexcept
2090	{ return {__m, __wdi}; }
2091
2092	friend constexpr month_weekday
2093	operator/(int __m, const chrono::weekday_indexed& __wdi) noexcept
2094	{ return chrono::month(unsigned(__m)) / __wdi; }
2095
2096	friend constexpr month_weekday
2097	operator/(const chrono::weekday_indexed& __wdi,
2098	const chrono::month& __m) noexcept
2099	{ return __m / __wdi; }
2100
2101	friend constexpr month_weekday
2102	operator/(const chrono::weekday_indexed& __wdi, int __m) noexcept
2103	{ return __m / __wdi; }
2104
2105	friend constexpr year_month_weekday
2106	operator/(int __y, const month_weekday& __mwd) noexcept;
2107
2108	friend constexpr year_month_weekday
2109	operator/(const month_weekday& __mwd, int __y) noexcept;
2110
2111	// TODO: Implement operator<<.
2112	};
2113
2114	// MONTH_WEEKDAY_LAST
2115
2116	class month_weekday_last
2117	{
2118	private:
2119	chrono::month _M_m;
2120	chrono::weekday_last _M_wdl;
2121
2122	public:
2123	constexpr
2124	month_weekday_last(const chrono::month& __m,
2125	const chrono::weekday_last& __wdl) noexcept
2126	:_M_m{__m}, _M_wdl{__wdl}
2127	{ }
2128
2129	constexpr chrono::month
2130	month() const noexcept
2131	{ return _M_m; }
2132
2133	constexpr chrono::weekday_last
2134	weekday_last() const noexcept
2135	{ return _M_wdl; }
2136
2137	constexpr bool
2138	ok() const noexcept
2139	{ return _M_m.ok() && _M_wdl.ok(); }
2140
2141	friend constexpr bool
2142	operator==(const month_weekday_last& __x,
2143	const month_weekday_last& __y) noexcept
2144	{
2145	return __x.month() == __y.month()
2146	&& __x.weekday_last() == __y.weekday_last();
2147	}
2148
2149	friend constexpr month_weekday_last
2150	operator/(const chrono::month& __m,
2151	const chrono::weekday_last& __wdl) noexcept
2152	{ return {__m, __wdl}; }
2153
2154	friend constexpr month_weekday_last
2155	operator/(int __m, const chrono::weekday_last& __wdl) noexcept
2156	{ return chrono::month(unsigned(__m)) / __wdl; }
2157
2158	friend constexpr month_weekday_last
2159	operator/(const chrono::weekday_last& __wdl,
2160	const chrono::month& __m) noexcept
2161	{ return __m / __wdl; }
2162
2163	friend constexpr month_weekday_last
2164	operator/(const chrono::weekday_last& __wdl, int __m) noexcept
2165	{ return chrono::month(unsigned(__m)) / __wdl; }
2166
2167	friend constexpr year_month_weekday_last
2168	operator/(int __y, const month_weekday_last& __mwdl) noexcept;
2169
2170	friend constexpr year_month_weekday_last
2171	operator/(const month_weekday_last& __mwdl, int __y) noexcept;
2172
2173	// TODO: Implement operator<<.
2174	};
2175
2176	// YEAR_MONTH
2177
2178	namespace __detail
2179	{
2180	// [time.cal.ym], [time.cal.ymd], etc constrain the 'months'-based
2181	// addition/subtraction operator overloads like so:
2182	//
2183	// Constraints: if the argument supplied by the caller for the months
2184	// parameter is convertible to years, its implicit conversion sequence
2185	// to years is worse than its implicit conversion sequence to months.
2186	//
2187	// We realize this constraint by templatizing the 'months'-based
2188	// overloads (using a dummy defaulted template parameter), so that
2189	// overload resolution doesn't select the 'months'-based overload unless
2190	// the implicit conversion sequence to 'months' is better than that to
2191	// 'years'.
2192	using __months_years_conversion_disambiguator = void;
2193	}
2194
2195	class year_month
2196	{
2197	private:
2198	chrono::year _M_y;
2199	chrono::month _M_m;
2200
2201	public:
2202	year_month() = default;
2203
2204	constexpr
2205	year_month(const chrono::year& __y, const chrono::month& __m) noexcept
2206	: _M_y{__y}, _M_m{__m}
2207	{ }
2208
2209	constexpr chrono::year
2210	year() const noexcept
2211	{ return _M_y; }
2212
2213	constexpr chrono::month
2214	month() const noexcept
2215	{ return _M_m; }
2216
2217	template<typename = __detail::__months_years_conversion_disambiguator>
2218	constexpr year_month&
2219	operator+=(const months& __dm) noexcept
2220	{
2221	*this = *this + __dm;
2222	return *this;
2223	}
2224
2225	template<typename = __detail::__months_years_conversion_disambiguator>
2226	constexpr year_month&
2227	operator-=(const months& __dm) noexcept
2228	{
2229	*this = *this - __dm;
2230	return *this;
2231	}
2232
2233	constexpr year_month&
2234	operator+=(const years& __dy) noexcept
2235	{
2236	*this = *this + __dy;
2237	return *this;
2238	}
2239
2240	constexpr year_month&
2241	operator-=(const years& __dy) noexcept
2242	{
2243	*this = *this - __dy;
2244	return *this;
2245	}
2246
2247	constexpr bool
2248	ok() const noexcept
2249	{ return _M_y.ok() && _M_m.ok(); }
2250
2251	friend constexpr bool
2252	operator==(const year_month& __x, const year_month& __y) noexcept
2253	{ return __x.year() == __y.year() && __x.month() == __y.month(); }
2254
2255	friend constexpr strong_ordering
2256	operator<=>(const year_month& __x, const year_month& __y) noexcept
2257	= default;
2258
2259	template<typename = __detail::__months_years_conversion_disambiguator>
2260	friend constexpr year_month
2261	operator+(const year_month& __ym, const months& __dm) noexcept
2262	{
2263	// TODO: Optimize?
2264	auto __m = __ym.month() + __dm;
2265	auto __i = int(unsigned(__ym.month())) - 1 + __dm.count();
2266	auto __y = (__i < 0
2267	? __ym.year() + years{(__i - 11) / 12}
2268	: __ym.year() + years{__i / 12});
2269	return __y / __m;
2270	}
2271
2272	template<typename = __detail::__months_years_conversion_disambiguator>
2273	friend constexpr year_month
2274	operator+(const months& __dm, const year_month& __ym) noexcept
2275	{ return __ym + __dm; }
2276
2277	template<typename = __detail::__months_years_conversion_disambiguator>
2278	friend constexpr year_month
2279	operator-(const year_month& __ym, const months& __dm) noexcept
2280	{ return __ym + -__dm; }
2281
2282	friend constexpr months
2283	operator-(const year_month& __x, const year_month& __y) noexcept
2284	{
2285	return (__x.year() - __y.year()
2286	+ months{static_cast<int>(unsigned{__x.month()})
2287	- static_cast<int>(unsigned{__y.month()})});
2288	}
2289
2290	friend constexpr year_month
2291	operator+(const year_month& __ym, const years& __dy) noexcept
2292	{ return (__ym.year() + __dy) / __ym.month(); }
2293
2294	friend constexpr year_month
2295	operator+(const years& __dy, const year_month& __ym) noexcept
2296	{ return __ym + __dy; }
2297
2298	friend constexpr year_month
2299	operator-(const year_month& __ym, const years& __dy) noexcept
2300	{ return __ym + -__dy; }
2301
2302	friend constexpr year_month
2303	operator/(const chrono::year& __y, const chrono::month& __m) noexcept
2304	{ return {__y, __m}; }
2305
2306	friend constexpr year_month
2307	operator/(const chrono::year& __y, int __m) noexcept
2308	{ return {__y, chrono::month(unsigned(__m))}; }
2309
2310	friend constexpr year_month_day
2311	operator/(const year_month& __ym, int __d) noexcept;
2312
2313	friend constexpr year_month_day_last
2314	operator/(const year_month& __ym, last_spec) noexcept;
2315
2316	// TODO: Implement operator<<, from_stream.
2317	};
2318
2319	// YEAR_MONTH_DAY
2320
2321	class year_month_day
2322	{
2323	private:
2324	chrono::year _M_y;
2325	chrono::month _M_m;
2326	chrono::day _M_d;
2327
2328	static constexpr year_month_day _S_from_days(const days& __dp) noexcept;
2329
2330	constexpr days _M_days_since_epoch() const noexcept;
2331
2332	public:
2333	year_month_day() = default;
2334
2335	constexpr
2336	year_month_day(const chrono::year& __y, const chrono::month& __m,
2337	const chrono::day& __d) noexcept
2338	: _M_y{__y}, _M_m{__m}, _M_d{__d}
2339	{ }
2340
2341	constexpr
2342	year_month_day(const year_month_day_last& __ymdl) noexcept;
2343
2344	constexpr
2345	year_month_day(const sys_days& __dp) noexcept
2346	: year_month_day(_S_from_days(dp: __dp.time_since_epoch()))
2347	{ }
2348
2349	explicit constexpr
2350	year_month_day(const local_days& __dp) noexcept
2351	: year_month_day(sys_days{__dp.time_since_epoch()})
2352	{ }
2353
2354	template<typename = __detail::__months_years_conversion_disambiguator>
2355	constexpr year_month_day&
2356	operator+=(const months& __m) noexcept
2357	{
2358	*this = *this + __m;
2359	return *this;
2360	}
2361
2362	template<typename = __detail::__months_years_conversion_disambiguator>
2363	constexpr year_month_day&
2364	operator-=(const months& __m) noexcept
2365	{
2366	*this = *this - __m;
2367	return *this;
2368	}
2369
2370	constexpr year_month_day&
2371	operator+=(const years& __y) noexcept
2372	{
2373	*this = *this + __y;
2374	return *this;
2375	}
2376
2377	constexpr year_month_day&
2378	operator-=(const years& __y) noexcept
2379	{
2380	*this = *this - __y;
2381	return *this;
2382	}
2383
2384	constexpr chrono::year
2385	year() const noexcept
2386	{ return _M_y; }
2387
2388	constexpr chrono::month
2389	month() const noexcept
2390	{ return _M_m; }
2391
2392	constexpr chrono::day
2393	day() const noexcept
2394	{ return _M_d; }
2395
2396	constexpr
2397	operator sys_days() const noexcept
2398	{ return sys_days{_M_days_since_epoch()}; }
2399
2400	explicit constexpr
2401	operator local_days() const noexcept
2402	{ return local_days{sys_days{*this}.time_since_epoch()}; }
2403
2404	constexpr bool ok() const noexcept;
2405
2406	friend constexpr bool
2407	operator==(const year_month_day& __x, const year_month_day& __y) noexcept
2408	{
2409	return __x.year() == __y.year()
2410	&& __x.month() == __y.month()
2411	&& __x.day() == __y.day();
2412	}
2413
2414	friend constexpr strong_ordering
2415	operator<=>(const year_month_day& __x, const year_month_day& __y) noexcept
2416	= default;
2417
2418	template<typename = __detail::__months_years_conversion_disambiguator>
2419	friend constexpr year_month_day
2420	operator+(const year_month_day& __ymd, const months& __dm) noexcept
2421	{ return (__ymd.year() / __ymd.month() + __dm) / __ymd.day(); }
2422
2423	template<typename = __detail::__months_years_conversion_disambiguator>
2424	friend constexpr year_month_day
2425	operator+(const months& __dm, const year_month_day& __ymd) noexcept
2426	{ return __ymd + __dm; }
2427
2428	friend constexpr year_month_day
2429	operator+(const year_month_day& __ymd, const years& __dy) noexcept
2430	{ return (__ymd.year() + __dy) / __ymd.month() / __ymd.day(); }
2431
2432	friend constexpr year_month_day
2433	operator+(const years& __dy, const year_month_day& __ymd) noexcept
2434	{ return __ymd + __dy; }
2435
2436	template<typename = __detail::__months_years_conversion_disambiguator>
2437	friend constexpr year_month_day
2438	operator-(const year_month_day& __ymd, const months& __dm) noexcept
2439	{ return __ymd + -__dm; }
2440
2441	friend constexpr year_month_day
2442	operator-(const year_month_day& __ymd, const years& __dy) noexcept
2443	{ return __ymd + -__dy; }
2444
2445	friend constexpr year_month_day
2446	operator/(const year_month& __ym, const chrono::day& __d) noexcept
2447	{ return {__ym.year(), __ym.month(), __d}; }
2448
2449	friend constexpr year_month_day
2450	operator/(const year_month& __ym, int __d) noexcept
2451	{ return __ym / chrono::day{unsigned(__d)}; }
2452
2453	friend constexpr year_month_day
2454	operator/(const chrono::year& __y, const month_day& __md) noexcept
2455	{ return __y / __md.month() / __md.day(); }
2456
2457	friend constexpr year_month_day
2458	operator/(int __y, const month_day& __md) noexcept
2459	{ return chrono::year{__y} / __md; }
2460
2461	friend constexpr year_month_day
2462	operator/(const month_day& __md, const chrono::year& __y) noexcept
2463	{ return __y / __md; }
2464
2465	friend constexpr year_month_day
2466	operator/(const month_day& __md, int __y) noexcept
2467	{ return chrono::year(__y) / __md; }
2468
2469	// TODO: Implement operator<<, from_stream.
2470	};
2471
2472	// Construct from days since 1970/01/01.
2473	// Proposition 6.3 of Neri and Schneider,
2474	// "Euclidean Affine Functions and Applications to Calendar Algorithms".
2475	// https://arxiv.org/abs/2102.06959
2476	constexpr year_month_day
2477	year_month_day::_S_from_days(const days& __dp) noexcept
2478	{
2479	constexpr auto __z2 = static_cast<uint32_t>(-1468000);
2480	constexpr auto __r2_e3 = static_cast<uint32_t>(536895458);
2481
2482	const auto __r0 = static_cast<uint32_t>(__dp.count()) + __r2_e3;
2483
2484	const auto __n1 = 4 * __r0 + 3;
2485	const auto __q1 = __n1 / 146097;
2486	const auto __r1 = __n1 % 146097 / 4;
2487
2488	constexpr auto __p32 = static_cast<uint64_t>(1) << 32;
2489	const auto __n2 = 4 * __r1 + 3;
2490	const auto __u2 = static_cast<uint64_t>(2939745) * __n2;
2491	const auto __q2 = static_cast<uint32_t>(__u2 / __p32);
2492	const auto __r2 = static_cast<uint32_t>(__u2 % __p32) / 2939745 / 4;
2493
2494	constexpr auto __p16 = static_cast<uint32_t>(1) << 16;
2495	const auto __n3 = 2141 * __r2 + 197913;
2496	const auto __q3 = __n3 / __p16;
2497	const auto __r3 = __n3 % __p16 / 2141;
2498
2499	const auto __y0 = 100 * __q1 + __q2;
2500	const auto __m0 = __q3;
2501	const auto __d0 = __r3;
2502
2503	const auto __j = __r2 >= 306;
2504	const auto __y1 = __y0 + __j;
2505	const auto __m1 = __j ? __m0 - 12 : __m0;
2506	const auto __d1 = __d0 + 1;
2507
2508	return year_month_day{chrono::year{static_cast<int>(__y1 + __z2)},
2509	chrono::month{__m1}, chrono::day{__d1}};
2510	}
2511
2512	// Days since 1970/01/01.
2513	// Proposition 6.2 of Neri and Schneider,
2514	// "Euclidean Affine Functions and Applications to Calendar Algorithms".
2515	// https://arxiv.org/abs/2102.06959
2516	constexpr days
2517	year_month_day::_M_days_since_epoch() const noexcept
2518	{
2519	auto constexpr __z2 = static_cast<uint32_t>(-1468000);
2520	auto constexpr __r2_e3 = static_cast<uint32_t>(536895458);
2521
2522	const auto __y1 = static_cast<uint32_t>(static_cast<int>(_M_y)) - __z2;
2523	const auto __m1 = static_cast<uint32_t>(static_cast<unsigned>(_M_m));
2524	const auto __d1 = static_cast<uint32_t>(static_cast<unsigned>(_M_d));
2525
2526	const auto __j = static_cast<uint32_t>(__m1 < 3);
2527	const auto __y0 = __y1 - __j;
2528	const auto __m0 = __j ? __m1 + 12 : __m1;
2529	const auto __d0 = __d1 - 1;
2530
2531	const auto __q1 = __y0 / 100;
2532	const auto __yc = 1461 * __y0 / 4 - __q1 + __q1 / 4;
2533	const auto __mc = (979 *__m0 - 2919) / 32;
2534	const auto __dc = __d0;
2535
2536	return days{static_cast<int32_t>(__yc + __mc + __dc - __r2_e3)};
2537	}
2538
2539	// YEAR_MONTH_DAY_LAST
2540
2541	class year_month_day_last
2542	{
2543	private:
2544	chrono::year _M_y;
2545	chrono::month_day_last _M_mdl;
2546
2547	public:
2548	constexpr
2549	year_month_day_last(const chrono::year& __y,
2550	const chrono::month_day_last& __mdl) noexcept
2551	: _M_y{__y}, _M_mdl{__mdl}
2552	{ }
2553
2554	template<typename = __detail::__months_years_conversion_disambiguator>
2555	constexpr year_month_day_last&
2556	operator+=(const months& __m) noexcept
2557	{
2558	*this = *this + __m;
2559	return *this;
2560	}
2561
2562	template<typename = __detail::__months_years_conversion_disambiguator>
2563	constexpr year_month_day_last&
2564	operator-=(const months& __m) noexcept
2565	{
2566	*this = *this - __m;
2567	return *this;
2568	}
2569
2570	constexpr year_month_day_last&
2571	operator+=(const years& __y) noexcept
2572	{
2573	*this = *this + __y;
2574	return *this;
2575	}
2576
2577	constexpr year_month_day_last&
2578	operator-=(const years& __y) noexcept
2579	{
2580	*this = *this - __y;
2581	return *this;
2582	}
2583
2584	constexpr chrono::year
2585	year() const noexcept
2586	{ return _M_y; }
2587
2588	constexpr chrono::month
2589	month() const noexcept
2590	{ return _M_mdl.month(); }
2591
2592	constexpr chrono::month_day_last
2593	month_day_last() const noexcept
2594	{ return _M_mdl; }
2595
2596	// Return A day representing the last day of this year, month pair.
2597	constexpr chrono::day
2598	day() const noexcept
2599	{
2600	const auto __m = static_cast<unsigned>(month());
2601
2602	// Excluding February, the last day of month __m is either 30 or 31 or,
2603	// in another words, it is 30 + b = 30 | b, where b is in {0, 1}.
2604
2605	// If __m in {1, 3, 4, 5, 6, 7}, then b is 1 if, and only if __m is odd.
2606	// Hence, b = __m & 1 = (__m ^ 0) & 1.
2607
2608	// If __m in {8, 9, 10, 11, 12}, then b is 1 if, and only if __m is even.
2609	// Hence, b = (__m ^ 1) & 1.
2610
2611	// Therefore, b = (__m ^ c) & 1, where c = 0, if __m < 8, or c = 1 if
2612	// __m >= 8, that is, c = __m >> 3.
2613
2614	// The above mathematically justifies this implementation whose
2615	// performance does not depend on look-up tables being on the L1 cache.
2616	return chrono::day{__m != 2 ? ((__m ^ (__m >> 3)) & 1) | 30
2617	: _M_y.is_leap() ? 29 : 28};
2618	}
2619
2620	constexpr
2621	operator sys_days() const noexcept
2622	{ return sys_days{year() / month() / day()}; }
2623
2624	explicit constexpr
2625	operator local_days() const noexcept
2626	{ return local_days{sys_days{*this}.time_since_epoch()}; }
2627
2628	constexpr bool
2629	ok() const noexcept
2630	{ return _M_y.ok() && _M_mdl.ok(); }
2631
2632	friend constexpr bool
2633	operator==(const year_month_day_last& __x,
2634	const year_month_day_last& __y) noexcept
2635	{
2636	return __x.year() == __y.year()
2637	&& __x.month_day_last() == __y.month_day_last();
2638	}
2639
2640	friend constexpr strong_ordering
2641	operator<=>(const year_month_day_last& __x,
2642	const year_month_day_last& __y) noexcept
2643	= default;
2644
2645	template<typename = __detail::__months_years_conversion_disambiguator>
2646	friend constexpr year_month_day_last
2647	operator+(const year_month_day_last& __ymdl,
2648	const months& __dm) noexcept
2649	{ return (__ymdl.year() / __ymdl.month() + __dm) / last; }
2650
2651	template<typename = __detail::__months_years_conversion_disambiguator>
2652	friend constexpr year_month_day_last
2653	operator+(const months& __dm,
2654	const year_month_day_last& __ymdl) noexcept
2655	{ return __ymdl + __dm; }
2656
2657	template<typename = __detail::__months_years_conversion_disambiguator>
2658	friend constexpr year_month_day_last
2659	operator-(const year_month_day_last& __ymdl,
2660	const months& __dm) noexcept
2661	{ return __ymdl + -__dm; }
2662
2663	friend constexpr year_month_day_last
2664	operator+(const year_month_day_last& __ymdl,
2665	const years& __dy) noexcept
2666	{ return {__ymdl.year() + __dy, __ymdl.month_day_last()}; }
2667
2668	friend constexpr year_month_day_last
2669	operator+(const years& __dy,
2670	const year_month_day_last& __ymdl) noexcept
2671	{ return __ymdl + __dy; }
2672
2673	friend constexpr year_month_day_last
2674	operator-(const year_month_day_last& __ymdl,
2675	const years& __dy) noexcept
2676	{ return __ymdl + -__dy; }
2677
2678	friend constexpr year_month_day_last
2679	operator/(const year_month& __ym, last_spec) noexcept
2680	{ return {__ym.year(), chrono::month_day_last{__ym.month()}}; }
2681
2682	friend constexpr year_month_day_last
2683	operator/(const chrono::year& __y,
2684	const chrono::month_day_last& __mdl) noexcept
2685	{ return {__y, __mdl}; }
2686
2687	friend constexpr year_month_day_last
2688	operator/(int __y, const chrono::month_day_last& __mdl) noexcept
2689	{ return chrono::year(__y) / __mdl; }
2690
2691	friend constexpr year_month_day_last
2692	operator/(const chrono::month_day_last& __mdl,
2693	const chrono::year& __y) noexcept
2694	{ return __y / __mdl; }
2695
2696	friend constexpr year_month_day_last
2697	operator/(const chrono::month_day_last& __mdl, int __y) noexcept
2698	{ return chrono::year(__y) / __mdl; }
2699
2700	// TODO: Implement operator<<.
2701	};
2702
2703	// year_month_day ctor from year_month_day_last
2704	constexpr
2705	year_month_day::year_month_day(const year_month_day_last& __ymdl) noexcept
2706	: _M_y{__ymdl.year()}, _M_m{__ymdl.month()}, _M_d{__ymdl.day()}
2707	{ }
2708
2709	constexpr bool
2710	year_month_day::ok() const noexcept
2711	{
2712	if (!_M_y.ok() || !_M_m.ok())
2713	return false;
2714	return chrono::day{1} <= _M_d && _M_d <= (_M_y / _M_m / last).day();
2715	}
2716
2717	// YEAR_MONTH_WEEKDAY
2718
2719	class year_month_weekday
2720	{
2721	private:
2722	chrono::year _M_y;
2723	chrono::month _M_m;
2724	chrono::weekday_indexed _M_wdi;
2725
2726	static constexpr year_month_weekday
2727	_S_from_sys_days(const sys_days& __dp)
2728	{
2729	year_month_day __ymd{__dp};
2730	chrono::weekday __wd{__dp};
2731	auto __index = __wd[(unsigned{__ymd.day()} - 1) / 7 + 1];
2732	return {__ymd.year(), __ymd.month(), __index};
2733	}
2734
2735	public:
2736	year_month_weekday() = default;
2737
2738	constexpr
2739	year_month_weekday(const chrono::year& __y, const chrono::month& __m,
2740	const chrono::weekday_indexed& __wdi) noexcept
2741	: _M_y{__y}, _M_m{__m}, _M_wdi{__wdi}
2742	{ }
2743
2744	constexpr
2745	year_month_weekday(const sys_days& __dp) noexcept
2746	: year_month_weekday{_S_from_sys_days(__dp)}
2747	{ }
2748
2749	explicit constexpr
2750	year_month_weekday(const local_days& __dp) noexcept
2751	: year_month_weekday{sys_days{__dp.time_since_epoch()}}
2752	{ }
2753
2754	template<typename = __detail::__months_years_conversion_disambiguator>
2755	constexpr year_month_weekday&
2756	operator+=(const months& __m) noexcept
2757	{
2758	*this = *this + __m;
2759	return *this;
2760	}
2761
2762	template<typename = __detail::__months_years_conversion_disambiguator>
2763	constexpr year_month_weekday&
2764	operator-=(const months& __m) noexcept
2765	{
2766	*this = *this - __m;
2767	return *this;
2768	}
2769
2770	constexpr year_month_weekday&
2771	operator+=(const years& __y) noexcept
2772	{
2773	*this = *this + __y;
2774	return *this;
2775	}
2776
2777	constexpr year_month_weekday&
2778	operator-=(const years& __y) noexcept
2779	{
2780	*this = *this - __y;
2781	return *this;
2782	}
2783
2784	constexpr chrono::year
2785	year() const noexcept
2786	{ return _M_y; }
2787
2788	constexpr chrono::month
2789	month() const noexcept
2790	{ return _M_m; }
2791
2792	constexpr chrono::weekday
2793	weekday() const noexcept
2794	{ return _M_wdi.weekday(); }
2795
2796	constexpr unsigned
2797	index() const noexcept
2798	{ return _M_wdi.index(); }
2799
2800	constexpr chrono::weekday_indexed
2801	weekday_indexed() const noexcept
2802	{ return _M_wdi; }
2803
2804	constexpr
2805	operator sys_days() const noexcept
2806	{
2807	auto __d = sys_days{year() / month() / 1};
2808	return __d + (weekday() - chrono::weekday(__d)
2809	+ days{(static_cast<int>(index())-1)*7});
2810	}
2811
2812	explicit constexpr
2813	operator local_days() const noexcept
2814	{ return local_days{sys_days{*this}.time_since_epoch()}; }
2815
2816	constexpr bool
2817	ok() const noexcept
2818	{
2819	if (!_M_y.ok() || !_M_m.ok() || !_M_wdi.ok())
2820	return false;
2821	if (_M_wdi.index() <= 4)
2822	return true;
2823	days __d = (_M_wdi.weekday()
2824	- chrono::weekday{sys_days{_M_y / _M_m / 1}}
2825	+ days((_M_wdi.index()-1)*7 + 1));
2826	__glibcxx_assert(__d.count() >= 1);
2827	return __d.count() <= unsigned{(_M_y / _M_m / last).day()};
2828	}
2829
2830	friend constexpr bool
2831	operator==(const year_month_weekday& __x,
2832	const year_month_weekday& __y) noexcept
2833	{
2834	return __x.year() == __y.year()
2835	&& __x.month() == __y.month()
2836	&& __x.weekday_indexed() == __y.weekday_indexed();
2837	}
2838
2839	template<typename = __detail::__months_years_conversion_disambiguator>
2840	friend constexpr year_month_weekday
2841	operator+(const year_month_weekday& __ymwd, const months& __dm) noexcept
2842	{
2843	return ((__ymwd.year() / __ymwd.month() + __dm)
2844	/ __ymwd.weekday_indexed());
2845	}
2846
2847	template<typename = __detail::__months_years_conversion_disambiguator>
2848	friend constexpr year_month_weekday
2849	operator+(const months& __dm, const year_month_weekday& __ymwd) noexcept
2850	{ return __ymwd + __dm; }
2851
2852	friend constexpr year_month_weekday
2853	operator+(const year_month_weekday& __ymwd, const years& __dy) noexcept
2854	{ return {__ymwd.year() + __dy, __ymwd.month(), __ymwd.weekday_indexed()}; }
2855
2856	friend constexpr year_month_weekday
2857	operator+(const years& __dy, const year_month_weekday& __ymwd) noexcept
2858	{ return __ymwd + __dy; }
2859
2860	template<typename = __detail::__months_years_conversion_disambiguator>
2861	friend constexpr year_month_weekday
2862	operator-(const year_month_weekday& __ymwd, const months& __dm) noexcept
2863	{ return __ymwd + -__dm; }
2864
2865	friend constexpr year_month_weekday
2866	operator-(const year_month_weekday& __ymwd, const years& __dy) noexcept
2867	{ return __ymwd + -__dy; }
2868
2869	friend constexpr year_month_weekday
2870	operator/(const year_month& __ym,
2871	const chrono::weekday_indexed& __wdi) noexcept
2872	{ return {__ym.year(), __ym.month(), __wdi}; }
2873
2874	friend constexpr year_month_weekday
2875	operator/(const chrono::year& __y, const month_weekday& __mwd) noexcept
2876	{ return {__y, __mwd.month(), __mwd.weekday_indexed()}; }
2877
2878	friend constexpr year_month_weekday
2879	operator/(int __y, const month_weekday& __mwd) noexcept
2880	{ return chrono::year(__y) / __mwd; }
2881
2882	friend constexpr year_month_weekday
2883	operator/(const month_weekday& __mwd, const chrono::year& __y) noexcept
2884	{ return __y / __mwd; }
2885
2886	friend constexpr year_month_weekday
2887	operator/(const month_weekday& __mwd, int __y) noexcept
2888	{ return chrono::year(__y) / __mwd; }
2889
2890	// TODO: Implement operator<<.
2891	};
2892
2893	// YEAR_MONTH_WEEKDAY_LAST
2894
2895	class year_month_weekday_last
2896	{
2897	private:
2898	chrono::year _M_y;
2899	chrono::month _M_m;
2900	chrono::weekday_last _M_wdl;
2901
2902	public:
2903	constexpr
2904	year_month_weekday_last(const chrono::year& __y, const chrono::month& __m,
2905	const chrono::weekday_last& __wdl) noexcept
2906	: _M_y{__y}, _M_m{__m}, _M_wdl{__wdl}
2907	{ }
2908
2909	template<typename = __detail::__months_years_conversion_disambiguator>
2910	constexpr year_month_weekday_last&
2911	operator+=(const months& __m) noexcept
2912	{
2913	*this = *this + __m;
2914	return *this;
2915	}
2916
2917	template<typename = __detail::__months_years_conversion_disambiguator>
2918	constexpr year_month_weekday_last&
2919	operator-=(const months& __m) noexcept
2920	{
2921	*this = *this - __m;
2922	return *this;
2923	}
2924
2925	constexpr year_month_weekday_last&
2926	operator+=(const years& __y) noexcept
2927	{
2928	*this = *this + __y;
2929	return *this;
2930	}
2931
2932	constexpr year_month_weekday_last&
2933	operator-=(const years& __y) noexcept
2934	{
2935	*this = *this - __y;
2936	return *this;
2937	}
2938
2939	constexpr chrono::year
2940	year() const noexcept
2941	{ return _M_y; }
2942
2943	constexpr chrono::month
2944	month() const noexcept
2945	{ return _M_m; }
2946
2947	constexpr chrono::weekday
2948	weekday() const noexcept
2949	{ return _M_wdl.weekday(); }
2950
2951	constexpr chrono::weekday_last
2952	weekday_last() const noexcept
2953	{ return _M_wdl; }
2954
2955	constexpr
2956	operator sys_days() const noexcept
2957	{
2958	const auto __d = sys_days{_M_y / _M_m / last};
2959	return sys_days{(__d - (chrono::weekday{__d}
2960	- _M_wdl.weekday())).time_since_epoch()};
2961	}
2962
2963	explicit constexpr
2964	operator local_days() const noexcept
2965	{ return local_days{sys_days{*this}.time_since_epoch()}; }
2966
2967	constexpr bool
2968	ok() const noexcept
2969	{ return _M_y.ok() && _M_m.ok() && _M_wdl.ok(); }
2970
2971	friend constexpr bool
2972	operator==(const year_month_weekday_last& __x,
2973	const year_month_weekday_last& __y) noexcept
2974	{
2975	return __x.year() == __y.year()
2976	&& __x.month() == __y.month()
2977	&& __x.weekday_last() == __y.weekday_last();
2978	}
2979
2980	template<typename = __detail::__months_years_conversion_disambiguator>
2981	friend constexpr year_month_weekday_last
2982	operator+(const year_month_weekday_last& __ymwdl,
2983	const months& __dm) noexcept
2984	{
2985	return ((__ymwdl.year() / __ymwdl.month() + __dm)
2986	/ __ymwdl.weekday_last());
2987	}
2988
2989	template<typename = __detail::__months_years_conversion_disambiguator>
2990	friend constexpr year_month_weekday_last
2991	operator+(const months& __dm,
2992	const year_month_weekday_last& __ymwdl) noexcept
2993	{ return __ymwdl + __dm; }
2994
2995	friend constexpr year_month_weekday_last
2996	operator+(const year_month_weekday_last& __ymwdl,
2997	const years& __dy) noexcept
2998	{ return {__ymwdl.year() + __dy, __ymwdl.month(), __ymwdl.weekday_last()}; }
2999
3000	friend constexpr year_month_weekday_last
3001	operator+(const years& __dy,
3002	const year_month_weekday_last& __ymwdl) noexcept
3003	{ return __ymwdl + __dy; }
3004
3005	template<typename = __detail::__months_years_conversion_disambiguator>
3006	friend constexpr year_month_weekday_last
3007	operator-(const year_month_weekday_last& __ymwdl,
3008	const months& __dm) noexcept
3009	{ return __ymwdl + -__dm; }
3010
3011	friend constexpr year_month_weekday_last
3012	operator-(const year_month_weekday_last& __ymwdl,
3013	const years& __dy) noexcept
3014	{ return __ymwdl + -__dy; }
3015
3016	friend constexpr year_month_weekday_last
3017	operator/(const year_month& __ym,
3018	const chrono::weekday_last& __wdl) noexcept
3019	{ return {__ym.year(), __ym.month(), __wdl}; }
3020
3021	friend constexpr year_month_weekday_last
3022	operator/(const chrono::year& __y,
3023	const chrono::month_weekday_last& __mwdl) noexcept
3024	{ return {__y, __mwdl.month(), __mwdl.weekday_last()}; }
3025
3026	friend constexpr year_month_weekday_last
3027	operator/(int __y, const chrono::month_weekday_last& __mwdl) noexcept
3028	{ return chrono::year(__y) / __mwdl; }
3029
3030	friend constexpr year_month_weekday_last
3031	operator/(const chrono::month_weekday_last& __mwdl,
3032	const chrono::year& __y) noexcept
3033	{ return __y / __mwdl; }
3034
3035	friend constexpr year_month_weekday_last
3036	operator/(const chrono::month_weekday_last& __mwdl, int __y) noexcept
3037	{ return chrono::year(__y) / __mwdl; }
3038
3039	// TODO: Implement operator<<.
3040	};
3041
3042	// HH_MM_SS
3043
3044	namespace __detail
3045	{
3046	consteval long long
3047	__pow10(unsigned __n)
3048	{
3049	long long __r = 1;
3050	while (__n-- > 0)
3051	__r *= 10;
3052	return __r;
3053	}
3054	}
3055
3056	template<typename _Duration>
3057	class hh_mm_ss
3058	{
3059	private:
3060	static constexpr int
3061	_S_fractional_width()
3062	{
3063	int __multiplicity_2 = 0;
3064	int __multiplicity_5 = 0;
3065	auto __den = _Duration::period::den;
3066	while ((__den % 2) == 0)
3067	{
3068	++__multiplicity_2;
3069	__den /= 2;
3070	}
3071	while ((__den % 5) == 0)
3072	{
3073	++__multiplicity_5;
3074	__den /= 5;
3075	}
3076	if (__den != 1)
3077	return 6;
3078
3079	int __width = (__multiplicity_2 > __multiplicity_5
3080	? __multiplicity_2 : __multiplicity_5);
3081	if (__width > 18)
3082	__width = 18;
3083	return __width;
3084	}
3085
3086	constexpr
3087	hh_mm_ss(_Duration __d, bool __is_neg)
3088	: _M_is_neg(__is_neg),
3089	_M_h (duration_cast<chrono::hours>(__d)),
3090	_M_m (duration_cast<chrono::minutes>(__d - hours())),
3091	_M_s (duration_cast<chrono::seconds>(__d - hours() - minutes()))
3092	{
3093	auto __ss = __d - hours() - minutes() - seconds();
3094	if constexpr (treat_as_floating_point_v<typename precision::rep>)
3095	_M_ss = __ss;
3096	else
3097	_M_ss = duration_cast<precision>(__ss);
3098	}
3099
3100	static constexpr _Duration
3101	_S_abs(_Duration __d)
3102	{
3103	if constexpr (numeric_limits<typename _Duration::rep>::is_signed)
3104	return chrono::abs(__d);
3105	else
3106	return __d;
3107	}
3108
3109	public:
3110	static constexpr unsigned fractional_width = {_S_fractional_width()};
3111
3112	using precision
3113	= duration<common_type_t<typename _Duration::rep,
3114	chrono::seconds::rep>,
3115	ratio<1, __detail::__pow10(n: fractional_width)>>;
3116
3117	constexpr
3118	hh_mm_ss() noexcept
3119	: hh_mm_ss{_Duration::zero()}
3120	{ }
3121
3122	constexpr explicit
3123	hh_mm_ss(_Duration __d)
3124	: hh_mm_ss(_S_abs(__d), __d < _Duration::zero())
3125	{ }
3126
3127	constexpr bool
3128	is_negative() const noexcept
3129	{ return _M_is_neg; }
3130
3131	constexpr chrono::hours
3132	hours() const noexcept
3133	{ return _M_h; }
3134
3135	constexpr chrono::minutes
3136	minutes() const noexcept
3137	{ return _M_m; }
3138
3139	constexpr chrono::seconds
3140	seconds() const noexcept
3141	{ return _M_s; }
3142
3143	constexpr precision
3144	subseconds() const noexcept
3145	{ return _M_ss; }
3146
3147	constexpr explicit
3148	operator precision() const noexcept
3149	{ return to_duration(); }
3150
3151	constexpr precision
3152	to_duration() const noexcept
3153	{
3154	if (_M_is_neg)
3155	return -(_M_h + _M_m + _M_s + _M_ss);
3156	else
3157	return _M_h + _M_m + _M_s + _M_ss;
3158	}
3159
3160	// TODO: Implement operator<<.
3161
3162	private:
3163	bool _M_is_neg;
3164	chrono::hours _M_h;
3165	chrono::minutes _M_m;
3166	chrono::seconds _M_s;
3167	precision _M_ss;
3168	};
3169	#endif // C++20
3170
3171	/// @} group chrono
3172	} // namespace chrono
3173
3174	#if __cplusplus > 201103L
3175
3176	#define __cpp_lib_chrono_udls 201304
3177
3178	inline namespace literals
3179	{
3180	/** ISO C++ 2014 namespace for suffixes for duration literals.
3181	*
3182	* These suffixes can be used to create `chrono::duration` values with
3183	* tick periods of hours, minutes, seconds, milliseconds, microseconds
3184	* or nanoseconds. For example, `std::chrono::seconds(5)` can be written
3185	* as `5s` after making the suffix visible in the current scope.
3186	* The suffixes can be made visible by a using-directive or
3187	* using-declaration such as:
3188	* - `using namespace std::chrono_literals;`
3189	* - `using namespace std::literals;`
3190	* - `using namespace std::chrono;`
3191	* - `using namespace std;`
3192	* - `using std::chrono_literals::operator""s;`
3193	*
3194	* The result of these suffixes on an integer literal is one of the
3195	* standard typedefs such as `std::chrono::hours`.
3196	* The result on a floating-point literal is a duration type with the
3197	* specified tick period and an unspecified floating-point representation,
3198	* for example `1.5e2ms` might be equivalent to
3199	* `chrono::duration<long double, chrono::milli>(1.5e2)`.
3200	*
3201	* @ingroup chrono
3202	*/
3203	inline namespace chrono_literals
3204	{
3205	/// @addtogroup chrono
3206	/// @{
3207
3208	#pragma GCC diagnostic push
3209	#pragma GCC diagnostic ignored "-Wliteral-suffix"
3210	/// @cond undocumented
3211	template<typename _Dur, char... _Digits>
3212	constexpr _Dur __check_overflow()
3213	{
3214	using _Val = __parse_int::_Parse_int<_Digits...>;
3215	constexpr typename _Dur::rep __repval = _Val::value;
3216	static_assert(__repval >= 0 && __repval == _Val::value,
3217	"literal value cannot be represented by duration type");
3218	return _Dur(__repval);
3219	}
3220	/// @endcond
3221
3222	/// Literal suffix for durations representing non-integer hours
3223	constexpr chrono::duration<long double, ratio<3600,1>>
3224	operator""h(long double __hours)
3225	{ return chrono::duration<long double, ratio<3600,1>>{__hours}; }
3226
3227	/// Literal suffix for durations of type `std::chrono::hours`
3228	template <char... _Digits>
3229	constexpr chrono::hours
3230	operator""h()
3231	{ return __check_overflow<chrono::hours, _Digits...>(); }
3232
3233	/// Literal suffix for durations representing non-integer minutes
3234	constexpr chrono::duration<long double, ratio<60,1>>
3235	operator""min(long double __mins)
3236	{ return chrono::duration<long double, ratio<60,1>>{__mins}; }
3237
3238	/// Literal suffix for durations of type `std::chrono::minutes`
3239	template <char... _Digits>
3240	constexpr chrono::minutes
3241	operator""min()
3242	{ return __check_overflow<chrono::minutes, _Digits...>(); }
3243
3244	/// Literal suffix for durations representing non-integer seconds
3245	constexpr chrono::duration<long double>
3246	operator""s(long double __secs)
3247	{ return chrono::duration<long double>{__secs}; }
3248
3249	/// Literal suffix for durations of type `std::chrono::seconds`
3250	template <char... _Digits>
3251	constexpr chrono::seconds
3252	operator""s()
3253	{ return __check_overflow<chrono::seconds, _Digits...>(); }
3254
3255	/// Literal suffix for durations representing non-integer milliseconds
3256	constexpr chrono::duration<long double, milli>
3257	operator""ms(long double __msecs)
3258	{ return chrono::duration<long double, milli>{__msecs}; }
3259
3260	/// Literal suffix for durations of type `std::chrono::milliseconds`
3261	template <char... _Digits>
3262	constexpr chrono::milliseconds
3263	operator""ms()
3264	{ return __check_overflow<chrono::milliseconds, _Digits...>(); }
3265
3266	/// Literal suffix for durations representing non-integer microseconds
3267	constexpr chrono::duration<long double, micro>
3268	operator""us(long double __usecs)
3269	{ return chrono::duration<long double, micro>{__usecs}; }
3270
3271	/// Literal suffix for durations of type `std::chrono::microseconds`
3272	template <char... _Digits>
3273	constexpr chrono::microseconds
3274	operator""us()
3275	{ return __check_overflow<chrono::microseconds, _Digits...>(); }
3276
3277	/// Literal suffix for durations representing non-integer nanoseconds
3278	constexpr chrono::duration<long double, nano>
3279	operator""ns(long double __nsecs)
3280	{ return chrono::duration<long double, nano>{__nsecs}; }
3281
3282	/// Literal suffix for durations of type `std::chrono::nanoseconds`
3283	template <char... _Digits>
3284	constexpr chrono::nanoseconds
3285	operator""ns()
3286	{ return __check_overflow<chrono::nanoseconds, _Digits...>(); }
3287
3288	#if __cplusplus > 201703L
3289	constexpr chrono::day
3290	operator""d(unsigned long long __d) noexcept
3291	{ return chrono::day{static_cast<unsigned>(__d)}; }
3292
3293	constexpr chrono::year
3294	operator""y(unsigned long long __y) noexcept
3295	{ return chrono::year{static_cast<int>(__y)}; }
3296	#endif // C++20
3297
3298	#pragma GCC diagnostic pop
3299	/// @}
3300	} // inline namespace chrono_literals
3301	} // inline namespace literals
3302
3303	namespace chrono
3304	{
3305	using namespace literals::chrono_literals;
3306	} // namespace chrono
3307
3308	#if __cplusplus > 201703L
3309	namespace chrono
3310	{
3311	/// @addtogroup chrono
3312	/// @{
3313
3314	// 12/24 HOURS FUNCTIONS
3315
3316	constexpr bool
3317	is_am(const hours& __h) noexcept
3318	{ return 0h <= __h && __h <= 11h; }
3319
3320	constexpr bool
3321	is_pm(const hours& __h) noexcept
3322	{ return 12h <= __h && __h <= 23h; }
3323
3324	constexpr hours
3325	make12(const hours& __h) noexcept
3326	{
3327	if (__h == 0h)
3328	return 12h;
3329	else if (__h > 12h)
3330	return __h - 12h;
3331	return __h;
3332	}
3333
3334	constexpr hours
3335	make24(const hours& __h, bool __is_pm) noexcept
3336	{
3337	if (!__is_pm)
3338	{
3339	if (__h == 12h)
3340	return 0h;
3341	else
3342	return __h;
3343	}
3344	else
3345	{
3346	if (__h == 12h)
3347	return __h;
3348	else
3349	return __h + 12h;
3350	}
3351	}
3352	/// @} group chrono
3353	} // namespace chrono
3354	#endif
3355
3356	#if __cplusplus >= 201703L
3357	namespace filesystem
3358	{
3359	struct __file_clock
3360	{
3361	using duration = chrono::nanoseconds;
3362	using rep = duration::rep;
3363	using period = duration::period;
3364	using time_point = chrono::time_point<__file_clock>;
3365	static constexpr bool is_steady = false;
3366
3367	static time_point
3368	now() noexcept
3369	{ return _S_from_sys(t: chrono::system_clock::now()); }
3370
3371	#if __cplusplus > 201703L
3372	template<typename _Dur>
3373	static
3374	chrono::file_time<_Dur>
3375	from_sys(const chrono::sys_time<_Dur>& __t) noexcept
3376	{ return _S_from_sys(__t); }
3377
3378	// For internal use only
3379	template<typename _Dur>
3380	static
3381	chrono::sys_time<_Dur>
3382	to_sys(const chrono::file_time<_Dur>& __t) noexcept
3383	{ return _S_to_sys(__t); }
3384	#endif // C++20
3385
3386	private:
3387	using __sys_clock = chrono::system_clock;
3388
3389	// This clock's (unspecified) epoch is 2174-01-01 00:00:00 UTC.
3390	// A signed 64-bit duration with nanosecond resolution gives roughly
3391	// +/- 292 years, which covers the 1901-2446 date range for ext4.
3392	static constexpr chrono::seconds _S_epoch_diff{6437664000};
3393
3394	protected:
3395	// For internal use only
3396	template<typename _Dur>
3397	static
3398	chrono::time_point<__file_clock, _Dur>
3399	_S_from_sys(const chrono::time_point<__sys_clock, _Dur>& __t) noexcept
3400	{
3401	using __file_time = chrono::time_point<__file_clock, _Dur>;
3402	return __file_time{__t.time_since_epoch()} - _S_epoch_diff;
3403	}
3404
3405	// For internal use only
3406	template<typename _Dur>
3407	static
3408	chrono::time_point<__sys_clock, _Dur>
3409	_S_to_sys(const chrono::time_point<__file_clock, _Dur>& __t) noexcept
3410	{
3411	using __sys_time = chrono::time_point<__sys_clock, _Dur>;
3412	return __sys_time{__t.time_since_epoch()} + _S_epoch_diff;
3413	}
3414	};
3415	} // namespace filesystem
3416	#endif // C++17
3417	#endif // C++14
3418
3419	_GLIBCXX_END_NAMESPACE_VERSION
3420	} // namespace std
3421
3422	#endif // C++11
3423
3424	#endif //_GLIBCXX_CHRONO
3425