std::chrono::treat_as_floating_point (3) - Linux Manuals

std::chrono::treat_as_floating_point: std::chrono::treat_as_floating_point

NAME

std::chrono::treat_as_floating_point - std::chrono::treat_as_floating_point

Synopsis

Defined in header <chrono>
template <class Rep> (since C++11)
struct treat_as_floating_point : std::is_floating_point<Rep> {};

The std::chrono::treat_as_floating_point trait helps determine if a duration can be converted to another duration with a different tick period.
Implicit conversions between two durations normally depends on the tick period of the durations. However, implicit conversions can happen regardless of tick period if std::chrono::treat_as_floating_point<Rep>::value == true.

Helper variable template

template< class Rep > (since C++17)
inline constexpr bool treat_as_floating_point_v = treat_as_floating_point<Rep>::value;

Example

// Run this code

  #include <iostream>
  #include <chrono>
  #include <thread>

  void timed_piece_of_code()
  {
      std::chrono::milliseconds simulated_work(2);
      std::this_thread::sleep_for(simulated_work);
  }

  int main()
  {
      auto start = std::chrono::high_resolution_clock::now();

      std::cout << "Running some timed piece of code..." << '\n';
      timed_piece_of_code();

      auto stop = std::chrono::high_resolution_clock::now();

      // A floating point milliseconds type
      using FpMilliseconds =
          std::chrono::duration<float, std::chrono::milliseconds::period>;

      static_assert(std::chrono::treat_as_floating_point<FpMilliseconds::rep>::value,
                    "Rep required to be floating point");

      // Note that implicit conversion is not allowed here
      auto i_ms = std::chrono::duration_cast<std::chrono::milliseconds>(stop - start);

      // Note that implicit conversion is allowed here
      auto f_ms = FpMilliseconds(stop - start);

      std::cout << "Time in milliseconds, using default rep: "
                << i_ms.count() << '\n';

      std::cout << "Time in milliseconds, using floating point rep: "
                << f_ms.count() << '\n';

  }

Possible output:

  Running some timed piece of code...
  Timing stats:
    Time in milliseconds, using default rep: 2
    Time in milliseconds, using floating point rep: 2.57307