NAME¶

std::chrono::time_point_cast - std::chrono::time_point_cast

Synopsis¶

Defined in header <chrono>
template <class ToDuration, class Clock, class Duration>
(since C++11)
std::chrono::time_point<Clock, ToDuration> (until C++14)

time_point_cast(const std::chrono::time_point<Clock, Duration> &t);
template <class ToDuration, class Clock, class Duration>

constexpr std::chrono::time_point<Clock, ToDuration> (since C++14)

time_point_cast(const std::chrono::time_point<Clock, Duration> &t);

Converts a std::chrono::time_point from one duration to another.

time_point_cast participates in overload resolution only if ToDuration is a
specialization of std::chrono::duration.

Parameters¶

t - time_point to convert from

Return value¶

std::chrono::time_point<Clock, ToDuration>(
std::chrono::duration_cast<ToDuration>(t.time_since_epoch())).

Example¶

// Run this code

#include <iostream>
#include <chrono>
using namespace std::chrono_literals;

using Clock = std::chrono::high_resolution_clock;
using Ms = std::chrono::milliseconds;
using Sec = std::chrono::seconds;

template<class Duration>
using TimePoint = std::chrono::time_point<Clock, Duration>;

inline void print_ms(const TimePoint<Ms>& time_point)
{
std::cout << time_point.time_since_epoch().count() << " ms\n";
}

int main()
{
TimePoint<Sec> time_point_sec{4s};

// implicit cast, no precision loss
TimePoint<Ms> time_point_ms{time_point_sec};
print_ms(time_point_ms); // 4000 ms

time_point_ms = TimePoint<Ms>{5756ms};
print_ms(time_point_ms); // 5756 ms

// explicit cast, need when precision loss may happen
// 5756 truncated to 5000
time_point_sec = std::chrono::time_point_cast<Sec>(time_point_ms);
print_ms(time_point_sec); // 5000 ms
}

Output:¶

4000 ms
5756 ms
5000 ms

See also¶

floor(std::chrono::time_point) converts a time_point to another, rounding down
(C++17) (function template)
ceil(std::chrono::time_point) converts a time_point to another, rounding up
(C++17) (function template)
round(std::chrono::time_point) converts a time_point to another, rounding to
(C++17) nearest, ties to even
(function template)
duration_cast converts a duration to another, with a different tick
(C++11) interval
(function template)