std::chrono::duration<Rep,Period>::duration
From cppreference.com
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Date and time library
(C++11)
(C++20)
(C++20)
(C++11)
(C++11)
(C++11)
(C++20)
(C++20)
(C++20)
(C++11)
(C++20)
(C++20)
(C++20)
(C++20)(C++20)
(C++20)(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)(C++20)
(C++20)
(C++20)
(C++20)
(C++20)(C++20)(C++20)(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
std::chrono::duration
Non-member functions
Helper classes
Member functions
duration::duration
(until C++20)(C++20)
(C++20)
(C++17)
(C++17)
(C++17)
(C++17)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++20)
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)
constexpr explicit duration( const Rep2& r );
template< class Rep2, class Period2 >
constexpr duration( const duration<Rep2, Period2>& d );
(4)
(since C++11)
constexpr duration( const duration<Rep2, Period2>& d );
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:[1]
- 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:[2]
- 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.
- ↑ 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, or
Period2is exactly divisible byPeriod.
Contents
[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 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 }
[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 |