2.1 KiB
[time.traits.specializations]
30 Time library [time]
30.4 Time-related traits [time.traits]
30.4.3 Specializations of common_type [time.traits.specializations]
template<class Rep1, class Period1, class Rep2, class Period2> struct common_type<chrono::duration<Rep1, Period1>, chrono::duration<Rep2, Period2>> { using type = chrono::duration<common_type_t<Rep1, Rep2>, see below>; };
The period of the duration indicated by this specialization ofcommon_type is the greatest common divisor of Period1 andPeriod2.
[Note 1:
This can be computed by forming a ratio of the greatest common divisor of Period1::num and Period2::num and the least common multiple of Period1::den and Period2::den.
â end note]
[Note 2:
The typedef name type is a synonym for theduration with the largest tick period possible where bothduration arguments will convert to it without requiring a division operation.
The representation of this type is intended to be able to hold any value resulting from this conversion with no truncation error, although floating-point durations can have round-off errors.
â end note]
template<class Clock, class Duration1, class Duration2> struct common_type<chrono::time_point<Clock, Duration1>, chrono::time_point<Clock, Duration2>> { using type = chrono::time_point<Clock, common_type_t<Duration1, Duration2>>; };
The common type of two time_point types is a time_point with the same clock as the two types and the common type of their two durations.