std::common_type(std::chrono::duration)

 

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std::chrono::duration

成员函数
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%=
非成员函数
operator+operator-operator*operator/operator% operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20 前)(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)

 

定义于头文件 <chrono>
template <class Rep1, class Period1, class Rep2, class Period2> struct common_type<std::chrono::duration<Rep1, Period1>,                    std::chrono::duration<Rep2, Period2>> {     typedef std::chrono::duration<         typename std::common_type<Rep1, Rep2>::type, /*see note*/> type; };		(C++11 起)

暴露名为 type 的类型，它是二个 std::chrono::duration 的共用类型，其周期为 Period1 与 Period2 的最大公约数。

注解

产生的时长的周期能通过构成 Period1::num 和 Period2::num 的最大公约数与 Period1::den 和 Period2::den 的最小公倍数的 ratio 计算。

示例

运行此代码

#include <iostream>
#include <chrono>
 
// std::chrono 已找到最大公约数，类似使用 std::common_type<> 。
// 我们令类型推导外化。 
 
template <typename T,typename S>
auto durationDiff(const T& t, const S& s)  -> typename std::common_type<T,S>::type
{
    typedef typename std::common_type<T,S>::type Common;
    return Common(t) - Common(s);
}
 
 
int main() 
{
    typedef std::chrono::milliseconds milliseconds;
    typedef std::chrono::microseconds microseconds;
 
    auto ms = milliseconds(30);
    auto us = microseconds(1100);
 
    std::cout << ms.count() << "ms - " << us.count() << "us = " 
              << durationDiff(ms,us).count() <<  "\n";
}

输出：

30ms - 1100us = 28900

参阅

common_type (C++11)

确定一组类型的公共类型 (类模板)