Skip to content

Latest commit

 

History

History
380 lines (250 loc) · 12.9 KB

duration-class.md

File metadata and controls

380 lines (250 loc) · 12.9 KB
description title ms.date f1_keywords helpviewer_keywords dev_langs
Learn more about: duration class
duration Class
01/05/2022
chrono/std::chrono::duration
chrono/std::chrono::duration::duration
chrono/std::chrono::duration::count
chrono/std::chrono::duration::max
chrono/std::chrono::duration::min
chrono/std::chrono::duration::zero
chrono/std::chrono::duration::operator-
chrono/std::chrono::duration::operator--
chrono/std::chrono::duration::operator%=
chrono/std::chrono::duration::operator*=
chrono/std::chrono::duration::operator+
chrono/std::chrono::duration::operator++
chrono/std::chrono::duration::operator+=
chrono/std::chrono::duration::operator-=
chrono/std::chrono::duration::operator=
std::chrono [C++], duration
C++

duration class

Measures a time span such as one minute, two hours, ten milliseconds, and so on.

A duration holds a time interval, which is the number of ticks over a time unit. For example, five minutes is five ticks, with each tick a minute apart. 42 seconds is 42 ticks, with each tick a second apart.

Syntax

template <class Rep, class Period> class duration;
template <class Rep, class Period = ratio<1>> class duration;
template <class Rep, class Period1, class Period2> class duration <duration<Rep, Period1>, Period2>;

Remarks

The template argument Rep describes the type that is used to hold the number of clock ticks in the interval. The template argument Period is an instantiation of ratio that describes the size of the interval that each tick represents.

Members

Constructors

Name Description
duration Constructs a duration object.

Functions

Name Description
count Returns the number of clock ticks in the time interval.
max Static. Returns the maximum allowable value of template parameter Rep.
min Static. Returns the lowest allowable value of template parameter Rep.
zero Static. In effect, returns Rep(0).

Operators

Name Description
duration::operator- Returns a copy of the duration object with a negated tick count.
duration::operator-- Decrements the stored tick count.
duration::operator-= Subtracts the tick count of a specified duration from the stored tick count.
duration::operator+ Returns *this.
duration::operator++ Increments the stored tick count.
duration::operator+= Adds the tick count of a specified duration to the stored tick count.
duration::operator= Assigns one duration to another.
duration::operator*= Multiplies the stored tick count by a specified value.
duration::operator/= Divides the stored tick count by the tick count of a specified duration object.
duration::operator%= Reduces the stored tick count modulo a specified value.

Non-members

Function templates

Name Description
abs Returns the absolute value of the duration.
ceil Returns the smallest representable duration that's greater than or equal to the specified duration.
duration_cast Casts a duration object to a specified target duration type.
floor Returns the greatest representable duration that's less than or equal to the specified duration.
from_stream Parse a duration from the given stream using the specified format.
round Rounds the specified duration to the nearest representable duration in the target type.

Operators

Name Description
operator+ After converting the durations being added to their common type, returns a duration with a tick count equal to the sum of the converted tick counts.
operator- After converting the durations being subtracted to their common type, returns a duration with a tick count equal to the number of ticks in the RHS duration subtracted from the number of ticks in the LHS duration.
operator* After converting the durations being multiplied to their common type, returns a duration with a tick count equal to the multiplication of the converted tick counts.
operator/ After converting the durations being divided to their common type, returns a duration with a tick count equal to the division of the converted tick counts.
operator% After converting the duration and the divisor to their common type, returns a duration with a tick count equal to the remainder of the division.
operator== After converting the duration types being compared to their common type, determines if the number of ticks are equal.
operator!= Determine if duration isn't equal to another.
operator< Determine if one duration is less than another.
operator<= Determine if one duration is less than or equal to another.
operator> Determine if one duration is greater than another.
operator>= Determine if one duration is greater than or equal to another.
operator<=> Compare one duration against another duration. The >, >=, <=, <, != operators are synthesized by the compiler.
operator<< Output a duration to the given stream.

Convenience type aliases

Name Description
duration::period A synonym for the template parameter Period.
duration::rep A synonym for the template parameter Rep.

Requirements

Header: <chrono>

Namespace: std::chrono

duration::count

Retrieves the number of clock ticks in the time interval.

constexpr Rep count() const;

Return value

The number of clock ticks in the time interval.

duration::duration constructor

Constructs a duration object.

1) constexpr duration() = default;
2) constexpr duration(const duration& d) = default;

3) template <class Rep2>
constexpr explicit duration(const Rep2& R);

4) template <class Rep2, class Period2>
constexpr duration(const duration<Rep2, Period2>& Dur);

Parameters

Dur
The number of ticks of period specified by Period2.

Period2
A std::ratio template specialization to represent the tick period in units of seconds.

R
The number of ticks of default period.

Rep2
An arithmetic type to represent the number of ticks.

Remarks

1) The default constructor constructs an object that is uninitialized. Value initialization by using empty braces initializes an object that represents a time interval of zero clock ticks.

2) The copy constructor makes a bitwise copy of d.

3) Constructs an object that represents a time interval of R clock ticks using a default period of std::ratio<1>. To avoid round-off of tick counts, it's an error to construct a duration object from a representation type Rep2 that can be treated as a floating-point type when duration::rep cannot be treated as a floating-point type.

4) Constructs an object that represents a time interval whose length is the time interval that is specified by Dur. To avoid truncation of tick counts, it's an error to construct a duration object from another duration object whose type is incommensurable with the target type.

A duration type D1 is incommensurable with another duration type D2 if D2 cannot be treated as a floating-point type and ratio_divide<D1::period, D2::period>::type::den isn't 1.

Unless Rep2 is implicitly convertible to rep and either treat_as_floating_point<rep>holds true or treat_as_floating_point<Rep2>holds false, the second constructor doesn't participate in overload resolution. For more information, see <type_traits>.

Unless no overflow is induced in the conversion and treat_as_floating_point<rep>holds true, or both ratio_divide<Period2, period>::den equals 1 and treat_as_floating_point<Rep2>holds false, the third constructor doesn't participate in overload resolution. For more information, see <type_traits>.

Example: Create a duration

// compile using: /std:c++latest
#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
    // create a duration that tracks ticks as 1/10ths of a second
    duration<int, std::ratio<1, 10>> tenths{ 5 };
    std::cout << tenths << '\n';

    hours h{12}; // hours is a convenience duration typedef 
    auto h2 = 3h; // 'h' is a convenience operator. h2 is a duration<int, std::ratio<3600,1>>

    std::cout << h << ":" << h2 << '\n';

    return 0;
}
5ds
3h:3h

duration::max

Static method that returns the upper bound for values of template parameter type Rep.

static constexpr duration max();

Return value

In effect, returns duration(duration_values<rep>::max()).

duration::min

Static method that returns the lower bound for values of template parameter type Rep.

static constexpr duration min();

Return value

In effect, returns duration(duration_values<rep>::min()).

duration::operator-

Returns a copy of the duration object with a negated tick count.

constexpr duration operator-() const;

duration::operator--

Decrements the stored tick count.

1) duration& operator--();
2) duration operator--(int);

Return value

1) Returns *this. 2) Returns a copy of *this before the decrement.

duration::operator%=

Reduces the stored tick count modulo the specified value.

1) duration& operator%=(const rep& Div);
2) duration& operator%=(const duration& Div);

Parameters

Div
1) Div a tick count. 2) Div a duration that contains a tick count.

Return value

The duration object after the modulo operation is done.

duration::operator*=

Multiplies the stored tick count by a specified value.

duration& operator*=(const rep& Mult);

Parameters

Mult
A value of the type that is specified by duration::rep.

Return value

The duration object after the multiplication is done.

duration::operator/=

Divides the stored tick count by a specified value.

duration& operator/=(const rep& Div);

Parameters

Div
A value of the type that is specified by duration::rep.

Return value

The duration object after the division is done.

duration::operator+

Returns *this.

constexpr duration operator+() const;

Return value

*this

duration::operator++

Increments the stored tick count.

1) duration& operator++();
2) duration operator++(int);

Return value

1) Returns *this. 2) Returns a copy of *this before the increment.

duration::operator+=

Adds the tick count of a specified duration object to the stored tick count.

duration& operator+=(const duration& Dur);

Parameters

Dur
A duration object.

Return value

The duration object after the addition is done.

duration::operator-=

Subtracts the tick count of a specified duration object from the stored tick count.

duration& operator-=(const duration& Dur);

Parameters

Dur
A duration object.

Return value

The duration object after the subtraction is done.

duration::zero

Returns duration(duration_values<rep>::zero()).

static constexpr duration zero();

duration::operator=

Assigns one duration to another.

duration& operator=(const duration &other) = default;

Parameters

other
The duration object to copy.

Return value

The LHS duration object.

See also

<chrono>
Convenience duration typedefs such as minutes, seconds, and more
Convenience literals for hours, minutes, and more
duration_values structure
Header Files Reference