std::chrono::treat_as_floating_point

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

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

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

See also

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