std::chrono::treat_as_floating_point

 

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std::chrono::duration

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duration::duration duration::operator= duration::count duration::zero duration::min duration::max duration::operator+duration::operator-	duration::operator++duration::operator-- duration::operator+=duration::operator-=duration::operator*=duration::operator/=duration::operator%=
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operator+operator-operator*operator/operator% operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(C++20) operator<< (C++20)	duration_cast floor (C++17) ceil (C++17) round (C++17) abs (C++17) operator""h (C++14) operator""min (C++14) operator""s (C++14) operator""ms (C++14) operator""us (C++14) operator""ns (C++14) from_stream (C++20)
辅助类
common_type treat_as_floating_point      duration_values	formatter<std::chrono::duration> (C++20) hash<std::chrono::duration> (C++26)

 

定义于头文件 <chrono>
template< class Rep > struct treat_as_floating_point : std::is_floating_point<Rep> {};		(C++11 起)

std::chrono::treat_as_floating_point 特性帮助确定是否可以将一个时长转换为另一个具有不同时钟周期的时长。

两个时长之间的隐式转换通常取决于时长的时钟周期。但是，如果 std::chrono::treat_as_floating_point<Rep>::value 为 true，则可以发生与时钟周期无关的隐式转换。

辅助变量模板

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

特化

std::chrono::treat_as_floating_point 可以为程序定义的类型特化。

示例

运行此代码

#include <chrono>
#include <iostream>
#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 << "Timing stats:\n";
 
    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';
}

可能的输出

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