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)
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hh_mm_ss (C++20)

Calendar
day (C++20)
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weekday (C++20)
operator/ (C++20)
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year_month_weekday (C++20)
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parse (C++20)

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tzdb (C++20)
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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)

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constexpr duration()=default;	(1)	(since C++11)
duration(const duration&)=default;	(2)	(since C++11)
template<class Rep2> constexprexplicit 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 newduration from one of several optional data sources.

1) The default constructor.

2) The copy constructor.

3) Constructs a duration withr ticks.

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

is_convertible<const Rep2&, Rep>::value istrue.
Any of the following conditions is satisfied:^[1]

std::chrono::treat_as_floating_point<Rep>::value istrue.
std::chrono::treat_as_floating_point<Rep2>::value isfalse.

4) Constructs a duration by convertingd to an appropriate period and tick count, as if bystd::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:^[2]

std::chrono::treat_as_floating_point<Rep>::value istrue.
All following conditions are satisfied:

std::ratio_divide<Period2, Period>::den is1.
std::chrono::treat_as_floating_point<Rep2>::value isfalse.

↑That is, a duration with an integer tick count cannot be constructed from a floating-point value, but a duration with a floating-point tick count can be constructed from an integer value.
↑That is, either the duration uses floating-point ticks, orPeriod2 is exactly divisible byPeriod.

[edit]Parameters

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

[edit]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 hourstd::chrono::milliseconds ms{3};// 3 millisecondsstd::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 ticksstd::chrono::duration<double,std::ratio<1,30>> hz30(3.5); // 3000 microseconds constructed from 3 millisecondsstd::chrono::microseconds us= ms;// error: 1/1000000 is not divisible by 1/1000//  std::chrono::milliseconds ms2 = usstd::chrono::duration<double,std::milli> ms2= us;// 3.0 milliseconds}

[edit]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