std::common_type<std::chrono::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)

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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)

 

Defined in header <chrono>
template< class Rep1, class Period1, class Rep2, class Period2 > struct common_type<std::chrono::duration<Rep1, Period1>, std::chrono::duration<Rep2, Period2>>;		(since C++11)

See More

Exposes the type named type, which is the common type of two std::chrono::durations, whose period is the greatest common divisor of Period1 and Period2.

Member types

Member type	Definition
type	std::chrono::duration<typename std::common_type<Rep1, Rep2>::type, /* see note */>

Note

The period of the resulting duration can be computed by forming a ratio of the greatest common divisor of Period1::num and Period2::num and the least common multiple of Period1::den and Period2::den.

Example

Run this code

#include <chrono>
#include <iostream>
#include <type_traits>

// std::chrono already finds the greatest common divisor,
// likely using std::common_type<>. We make the type
// deduction externally. 

template<typename T,typename S>
constexpr auto durationDiff(const T& t, const S& s)
    -> typename std::common_type<T,S>::type
{
    typedef typename std::common_type<T,S>::type Common;
    return Common(t) - Common(s);
}

int main() 
{
    using namespace std::literals;

    constexpr auto ms = 30ms;
    constexpr auto us = 1100us;
    constexpr auto diff = durationDiff(ms, us);

    std::cout << ms << " - " << us << " = " << diff << '\n';
}

Output:

30ms - 1100us = 28900us

See also

std::common_type<std::chrono::time_point> (C++11)	specializes the std::common_type trait (class template specialization)
common_type (C++11)	determines the common type of a group of types (class template)