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std::chrono..._point_cast(3)  C++ Standard Libary std::chrono..._point_cast(3)

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 ToDura-
       tion 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)

http://cppreference.com		  2022.07.31	  std::chrono..._point_cast(3)

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