std::chrono::treat_as_floating_point
定义于头文件 <chrono>
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template <class Rep> struct treat_as_floating_point : std::is_floating_point<Rep> {}; |
(C++11 起) | |
std::chrono::treat_as_floating_point
特性帮助确定时期是否能转换成拥有另一种不同计次周期的时期。
二个时期间的隐式转换通常依赖于时期的计次周期。然而若 std::chrono::treat_as_floating_point<Rep>::value == true 则可发生隐式转换,不管计次周期如何。
辅助变量模板
template< class Rep > inline constexpr bool treat_as_floating_point_v = treat_as_floating_point<Rep>::value; |
(C++17 起) | |
特化
可对程序定义类型特化 std::chrono::treat_as_floating_point
。
示例
运行此代码
#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(); // 浮点毫秒类型 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"); // 注意此处不允许隐式转换 auto i_ms = std::chrono::duration_cast<std::chrono::milliseconds>(stop - start); // 注意此处允许隐式转换 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'; }
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