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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 >

	std::chrono::time_point<Clock,				     ToDuration>
     (since C++11)
									       (un-
     til 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 <chrono>
      #include <iostream>
      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,  round-
     ing down
	(C++17) 		       (function template)
	ceil(std::chrono::time_point)	converts a time_point to another, round-
     ing up
	(C++17) 		       (function template)
	round(std::chrono::time_point) converts a time_point to another,  round-
     ing 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 	   2024.06.10	    std::chrono..._point_cast(3)
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