From Jason Turner

[time.clock]

C++20 → C++23 5.7 KB 54 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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C++ Weekly: Ep 397

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  1. tmp/tmpmv12x71z/{from.md → to.md} +20 -19
tmp/tmpmv12x71z/{from.md → to.md} RENAMED
@@ -1,8 +1,10 @@
1
  ## Clocks <a id="time.clock">[[time.clock]]</a>
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- The types defined in this subclause meet the *Cpp17TrivialClock*
 
 
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  requirements [[time.clock.req]] unless otherwise specified.
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  ### Class `system_clock` <a id="time.clock.system">[[time.clock.system]]</a>
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  #### Overview <a id="time.clock.system.overview">[[time.clock.system.overview]]</a>
@@ -80,13 +82,11 @@ template<class charT, class traits, class Duration>
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  `false`, and `Duration{1} < days{1}` is `true`.
81
 
82
  *Effects:* Equivalent to:
83
 
84
  ``` cpp
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- auto const dp = floor<days>(tp);
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- return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{} {}"),
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- year_month_day{dp}, hh_mm_ss{tp-dp});
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  ```
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  [*Example 1*:
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  ``` cpp
@@ -165,11 +165,12 @@ measure time since this epoch instead, one can add/subtract the constant
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166
  [*Example 1*:
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  `clock_cast<utc_clock>(sys_seconds{sys_days{1970y/January/1}}).time_since_epoch()`
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  is `0s`.
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  `clock_cast<utc_clock>(sys_seconds{sys_days{2000y/January/1}}).time_since_epoch()`
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- is `946'684'822s`, which is `10'957 * 86'400s + 22s`.
 
171
  — *end example*]
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  `utc_clock` is not a *Cpp17TrivialClock* unless the implementation can
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  guarantee that `utc_clock::now()` does not propagate an exception.
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@@ -237,11 +238,11 @@ template<class charT, class traits, class Duration>
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  ```
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  *Effects:* Equivalent to:
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241
  ``` cpp
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- return os << format(STATICALLY-WIDEN<charT>("{:%F %T}"), t);
243
  ```
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  [*Example 1*:
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  ``` cpp
@@ -408,11 +409,11 @@ template<class charT, class traits, class Duration>
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  ```
409
 
410
  *Effects:* Equivalent to:
411
 
412
  ``` cpp
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- return os << format(STATICALLY-WIDEN<charT>("{:%F %T}"), t);
414
  ```
415
 
416
  [*Example 1*:
417
 
418
  ``` cpp
@@ -506,11 +507,11 @@ template<class Duration>
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  ```
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508
  *Returns:*
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510
  ``` cpp
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- gps_time<common_type_t<Duration, seconds>>{t.time_since_epoch()} + 315964809s
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  ```
513
 
514
  [*Note 1*:
515
 
516
  ``` cpp
@@ -548,11 +549,11 @@ template<class charT, class traits, class Duration>
548
  ```
549
 
550
  *Effects:* Equivalent to:
551
 
552
  ``` cpp
553
- return os << format(STATICALLY-WIDEN<charT>("{:%F %T}"), t);
554
  ```
555
 
556
  [*Example 1*:
557
 
558
  ``` cpp
@@ -604,11 +605,11 @@ namespace std::chrono {
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  requirements [[time.clock.req]], and using a signed arithmetic type for
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  `file_clock::rep`. `file_clock` is used to create the `time_point`
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  system used for `file_time_type` [[filesystems]]. Its epoch is
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  unspecified, and `noexcept(file_clock::now())` is `true`.
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609
- [*Note 1*: The type that `file_clock` denotes may be in a different
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  namespace than `std::chrono`, such as `std::filesystem`. — *end note*]
611
 
612
  #### Member functions <a id="time.clock.file.members">[[time.clock.file.members]]</a>
613
 
614
  The type denoted by `file_clock` provides precisely one of the following
@@ -648,11 +649,11 @@ template<class charT, class traits, class Duration>
648
  ```
649
 
650
  *Effects:* Equivalent to:
651
 
652
  ``` cpp
653
- return os << format(STATICALLY-WIDEN<charT>("{:%F %T}"), t);
654
  ```
655
 
656
  ``` cpp
657
  template<class charT, class traits, class Duration, class Alloc = allocator<charT>>
658
  basic_istream<charT, traits>&
@@ -896,12 +897,12 @@ template<class Duration>
896
  -> decltype(SourceClock::to_sys(t));
897
  ```
898
 
899
  *Constraints:* `SourceClock::to_sys(t)` is well-formed.
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901
- *Mandates:* `SourceClock::to_sys(t)` returns a `sys_time<Duration>`,
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- where `Duration` is a valid `chrono::duration` specialization.
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904
  *Returns:* `SourceClock::to_sys(t)`.
905
 
906
  ``` cpp
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  template<class DestClock>
@@ -919,12 +920,12 @@ template<class Duration>
919
  ```
920
 
921
  *Constraints:* `DestClock::from_sys(t)` is well-formed.
922
 
923
  *Mandates:* `DestClock::from_sys(t)` returns a
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- `time_point<DestClock, Duration>`, where `Duration` is a valid
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- `chrono::duration` specialization.
926
 
927
  *Returns:* `DestClock::from_sys(t)`.
928
 
929
  #### Conversions between `utc_clock` and other clocks <a id="time.clock.cast.utc">[[time.clock.cast.utc]]</a>
930
 
@@ -943,12 +944,12 @@ template<class Duration>
943
  -> decltype(SourceClock::to_utc(t));
944
  ```
945
 
946
  *Constraints:* `SourceClock::to_utc(t)` is well-formed.
947
 
948
- *Mandates:* `SourceClock::to_utc(t)` returns a `utc_time<Duration>`,
949
- where `Duration` is a valid `chrono::duration` specialization.
950
 
951
  *Returns:* `SourceClock::to_utc(t)`.
952
 
953
  ``` cpp
954
  template<class DestClock>
@@ -966,12 +967,12 @@ template<class Duration>
966
  ```
967
 
968
  *Constraints:* `DestClock::from_utc(t)` is well-formed.
969
 
970
  *Mandates:* `DestClock::from_utc(t)` returns a
971
- `time_point<DestClock, Duration>`, where `Duration` is a valid
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- `chrono::duration` specialization.
973
 
974
  *Returns:* `DestClock::from_utc(t)`.
975
 
976
  #### Function template `clock_cast` <a id="time.clock.cast.fn">[[time.clock.cast.fn]]</a>
977
 
 
1
  ## Clocks <a id="time.clock">[[time.clock]]</a>
2
 
3
+ ### General <a id="time.clock.general">[[time.clock.general]]</a>
4
+
5
+ The types defined in [[time.clock]] meet the *Cpp17TrivialClock*
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  requirements [[time.clock.req]] unless otherwise specified.
7
 
8
  ### Class `system_clock` <a id="time.clock.system">[[time.clock.system]]</a>
9
 
10
  #### Overview <a id="time.clock.system.overview">[[time.clock.system.overview]]</a>
 
82
  `false`, and `Duration{1} < days{1}` is `true`.
83
 
84
  *Effects:* Equivalent to:
85
 
86
  ``` cpp
87
+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{:L%F %T}"), tp);
 
 
88
  ```
89
 
90
  [*Example 1*:
91
 
92
  ``` cpp
 
165
 
166
  [*Example 1*:
167
  `clock_cast<utc_clock>(sys_seconds{sys_days{1970y/January/1}}).time_since_epoch()`
168
  is `0s`.
169
  `clock_cast<utc_clock>(sys_seconds{sys_days{2000y/January/1}}).time_since_epoch()`
170
+ is `946'684'822s`,
171
+ which is `10'957 * 86'400s + 22s`.
172
  — *end example*]
173
 
174
  `utc_clock` is not a *Cpp17TrivialClock* unless the implementation can
175
  guarantee that `utc_clock::now()` does not propagate an exception.
176
 
 
238
  ```
239
 
240
  *Effects:* Equivalent to:
241
 
242
  ``` cpp
243
+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{:L%F %T}"), t);
244
  ```
245
 
246
  [*Example 1*:
247
 
248
  ``` cpp
 
409
  ```
410
 
411
  *Effects:* Equivalent to:
412
 
413
  ``` cpp
414
+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{:L%F %T}"), t);
415
  ```
416
 
417
  [*Example 1*:
418
 
419
  ``` cpp
 
507
  ```
508
 
509
  *Returns:*
510
 
511
  ``` cpp
512
+ utc_time<common_type_t<Duration, seconds>>{t.time_since_epoch()} + 315964809s
513
  ```
514
 
515
  [*Note 1*:
516
 
517
  ``` cpp
 
549
  ```
550
 
551
  *Effects:* Equivalent to:
552
 
553
  ``` cpp
554
+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{:L%F %T}"), t);
555
  ```
556
 
557
  [*Example 1*:
558
 
559
  ``` cpp
 
605
  requirements [[time.clock.req]], and using a signed arithmetic type for
606
  `file_clock::rep`. `file_clock` is used to create the `time_point`
607
  system used for `file_time_type` [[filesystems]]. Its epoch is
608
  unspecified, and `noexcept(file_clock::now())` is `true`.
609
 
610
+ [*Note 1*: The type that `file_clock` denotes can be in a different
611
  namespace than `std::chrono`, such as `std::filesystem`. — *end note*]
612
 
613
  #### Member functions <a id="time.clock.file.members">[[time.clock.file.members]]</a>
614
 
615
  The type denoted by `file_clock` provides precisely one of the following
 
649
  ```
650
 
651
  *Effects:* Equivalent to:
652
 
653
  ``` cpp
654
+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{:L%F %T}"), t);
655
  ```
656
 
657
  ``` cpp
658
  template<class charT, class traits, class Duration, class Alloc = allocator<charT>>
659
  basic_istream<charT, traits>&
 
897
  -> decltype(SourceClock::to_sys(t));
898
  ```
899
 
900
  *Constraints:* `SourceClock::to_sys(t)` is well-formed.
901
 
902
+ *Mandates:* `SourceClock::to_sys(t)` returns a `sys_time<Duration2>` for
903
+ some type `Duration2` [[time.point.general]].
904
 
905
  *Returns:* `SourceClock::to_sys(t)`.
906
 
907
  ``` cpp
908
  template<class DestClock>
 
920
  ```
921
 
922
  *Constraints:* `DestClock::from_sys(t)` is well-formed.
923
 
924
  *Mandates:* `DestClock::from_sys(t)` returns a
925
+ `time_point<DestClock, Duration2>` for some type `Duration2`
926
+ [[time.point.general]].
927
 
928
  *Returns:* `DestClock::from_sys(t)`.
929
 
930
  #### Conversions between `utc_clock` and other clocks <a id="time.clock.cast.utc">[[time.clock.cast.utc]]</a>
931
 
 
944
  -> decltype(SourceClock::to_utc(t));
945
  ```
946
 
947
  *Constraints:* `SourceClock::to_utc(t)` is well-formed.
948
 
949
+ *Mandates:* `SourceClock::to_utc(t)` returns a `utc_time<Duration2>` for
950
+ some type `Duration2` [[time.point.general]].
951
 
952
  *Returns:* `SourceClock::to_utc(t)`.
953
 
954
  ``` cpp
955
  template<class DestClock>
 
967
  ```
968
 
969
  *Constraints:* `DestClock::from_utc(t)` is well-formed.
970
 
971
  *Mandates:* `DestClock::from_utc(t)` returns a
972
+ `time_point<DestClock, Duration2>` for some type `Duration2`
973
+ [[time.point.general]].
974
 
975
  *Returns:* `DestClock::from_utc(t)`.
976
 
977
  #### Function template `clock_cast` <a id="time.clock.cast.fn">[[time.clock.cast.fn]]</a>
978