std::chrono::duration<Rep,Period>::duration

 

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Date and time library

Time point time_point (C++11) clock_time_conversion (C++20)   clock_cast (C++20) Duration duration (C++11) Clocks system_clock (C++11) steady_clock (C++11) is_clock (C++20) utc_clock (C++20) tai_clock (C++20) high_resolution_clock (C++11) gps_clock (C++20) file_clock (C++20) local_t (C++20) Time of day is_amis_pm (C++20)(C++20) make12make24 (C++20)(C++20) hh_mm_ss (C++20)

Calendar day (C++20) month (C++20) year (C++20) weekday (C++20) operator/ (C++20) year_month_day (C++20) year_month_day_last (C++20) year_month_weekday (C++20) year_month_weekday_last (C++20)   weekday_indexed (C++20) weekday_last (C++20) month_day (C++20) month_day_last (C++20) month_weekday (C++20) month_weekday_last (C++20) year_month (C++20) last_speclast (C++20)(C++20) chrono I/O parse (C++20)

Time zone tzdb (C++20) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20) sys_info (C++20) local_info (C++20) nonexistent_local_time (C++20) ambiguous_local_time (C++20) locate_zone (C++20) current_zone (C++20) time_zone (C++20) choose (C++20) zoned_traits (C++20) zoned_time (C++20) time_zone_link (C++20) leap_second (C++20) leap_second_info (C++20) get_leap_second_info (C++20) C-style date and time

 

std::chrono::duration

Member functions
duration::duration duration::operator= duration::count duration::zero duration::min duration::max duration::operator+duration::operator-	duration::operator++duration::operator-- duration::operator+=duration::operator-=duration::operator*=duration::operator/=duration::operator%=
Non-member functions
operator+operator-operator*operator/operator% operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(C++20) operator<< (C++20)	duration_cast floor (C++17) ceil (C++17) round (C++17) abs (C++17) operator""h (C++14) operator""min (C++14) operator""s (C++14) operator""ms (C++14) operator""us (C++14) operator""ns (C++14) from_stream (C++20)
Helper classes
common_type treat_as_floating_point      duration_values	formatter<std::chrono::duration> (C++20) hash<std::chrono::duration> (C++26)

 

constexpr duration() = default;	(1)	(since C++11)
duration( const duration& ) = default;	(2)	(since C++11)
template< class Rep2 > constexpr explicit duration( const Rep2& r );	(3)	(since C++11)
template< class Rep2, class Period2 > constexpr duration( const duration<Rep2, Period2>& d );	(4)	(since C++11)

Constructs a new duration from one of several optional data sources.

1) The default constructor.

2) The copy constructor.

3) Constructs a duration with r ticks.

This overload participates in overload resolution only if all following conditions are satisfied:

• is_convertible<const Rep2&, Rep>::value is true.
• Any of the following conditions is satisfied:

• std::chrono::treat_as_floating_point<Rep>::value is true.
• std::chrono::treat_as_floating_point<Rep2>::value is false.

4) Constructs a duration by converting d to an appropriate period and tick count, as if by std::chrono::duration_cast<duration>(d).count().

This overload participates in overload resolution only if no overflow is induced in the conversion, and any of the following conditions is satisfied:

• std::chrono::treat_as_floating_point<Rep>::value is true.
• All following conditions are satisfied:

• std::ratio_divide<Period2, Period>::den is 1.
• std::chrono::treat_as_floating_point<Rep2>::value is false.

Parameters

r	-	a tick count
d	-	a duration to copy from

Example

The following code shows several examples (both valid and invalid) of how to construct durations:

Run this code

#include <chrono>
 
int main()
{
    std::chrono::hours h(1); / one hour
    std::chrono::milliseconds ms{3}; / 3 milliseconds
    std::chrono::duration<int, std::kilo> ks(3); / 3000 seconds
 
    / error: treat_as_floating_point<int>::value == false,
    / This duration allows whole tick counts only
/  std::chrono::duration<int, std::kilo> d3(3.5);
 
    / 30Hz clock using fractional ticks
    std::chrono::duration<double, std::ratio<1, 30>> hz30(3.5);
 
    / 3000 microseconds constructed from 3 milliseconds
    std::chrono::microseconds us = ms;
    / error: 1/1000000 is not divisible by 1/1000
/  std::chrono::milliseconds ms2 = us
    std::chrono::duration<double, std::milli> ms2 = us; / 3.0 milliseconds
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2094	C++11	for overload (4), std::ratio_divide<Period2, period>::num might overflow when evaluating std::ratio_divide<Period2, period>::den	overload (4) does not participate in overload resolution in this case
LWG 3050	C++11	convertibility constraint used non-const xvalue	use const lvalues instead

See also

operator=

assigns the contents (public member function)

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