std::chrono::treat_as_floating_point

 

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treat_as_floating_point
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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 > 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

std::chrono::experimental::treat_as_floating_point_v (library fundamentals TS)

variable template alias of std::chrono::treat_as_floating_point::value (variable template)