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

 

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General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator> rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)    cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

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Time point
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Duration
duration (C++11)
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chrono I/O
parse (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)

 

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 is defaulted.

2) The copy constructor is defaulted (makes a bitwise copy of the tick count).

3) Constructs a duration with r ticks. Note that this constructor only participates in overload resolution if const Rep2& (the argument type) is implicitly convertible to rep (the type of this duration's ticks) and

• std::chrono::treat_as_floating_point<rep>::value is true, or
• 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)

4) Constructs a duration by converting d to an appropriate period and tick count, as if by std::chrono::duration_cast<duration>(d).count(). In order to prevent truncation during conversion, this constructor only participates in overload resolution if computation of the conversion factor (by std::ratio_divide<Period2, Period>) does not overflow and:

• std::chrono::treat_as_floating_point<rep>::value == true

or both:

• std::ratio_divide<Period2, period>::den == 1, and
• std::chrono::treat_as_floating_point<Rep2>::value == false.

(that is, either the duration uses floating-point ticks, or Period2 is exactly divisible by period)

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 3050	C++11	convertibility constraint used non-const xvalue	use const lvalues instead

See also

operator=

assigns the contents (public member function)