std::chrono::time_point_cast - cppreference.com

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# std::chrono::time_point_cast

From cppreference.com
< cpp‎ | chrono‎ | time point

template <class ToDuration, class Clock, class Duration> time_point<Clock, ToDuration> time_point_cast( const time_point<Clock, Duration> &t); |  | (since C++11) (until C++14)
template <class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> time_point_cast( const time_point<Clock, Duration> &t); |  | (since C++14)

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

### [edit] Parameters

t | - | `time_point` to convert from

### [edit] Return value

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

### [edit] Notes

`time_point_cast` will only participate in overload resolution if `ToDuration` is an instantiation of `duration`.

### [edit] Example

Run this code

    #include <iostream>
    #include <chrono>

    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(Sec(4));

        // 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>(Ms(5756));

        // explicit cast, need when precision loss may happens
        // 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
    5000 ms

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