C++：使用后缀设置时间

Question

告诉我，C ++ 11/14/17 中是否存在以下内容：

1）使用时间后缀设置时间

double time1 = 1s; // time1 = 1.0
double time2 = 2m; // time2 = 120.0
double time3 = 7ms; // time3 = 0.007 

2）获取设置后缀的时间字符串值

std::cout << getTime(time1); // cout 1s
std::cout << getTime(time2); // cout 2s
std::cout << getTime(time3); // cout 7ms

Answer 1

1. 是的，通过std::chrono_literals。

2. 不直接，但您可以打印typeid（可用于调试）或自己提供流持续时间的重载。

我在这里包含了显式重载operator<<，但作为@JeJo，它也可以使用模板来完成： https: //wandbox.org/permlink/o495eXlv4rQ3z6yP

#include <iostream>
#include <chrono>
#include <typeinfo>

using namespace std::chrono_literals;

// example overloads for streaming out durations
std::ostream& operator<<(std::ostream& os, const std::chrono::nanoseconds& v) {
    return os << v.count() << "ns";
}
std::ostream& operator<<(std::ostream& os, const std::chrono::microseconds& v) {
    return os << v.count() << "us";
}
std::ostream& operator<<(std::ostream& os, const std::chrono::milliseconds& v) {
    return os << v.count() << "ms";
}
std::ostream& operator<<(std::ostream& os, const std::chrono::seconds& v) {
    return os << v.count() << "s";
}
std::ostream& operator<<(std::ostream& os, const std::chrono::minutes& v) {
    return os << v.count() << "min";
}
std::ostream& operator<<(std::ostream& os, const std::chrono::hours& v) {
    return os << v.count() << "h";
}

int main() {
    auto time1 = 1s;
    auto time2 = 2min;
    auto time3 = 7ms;
    std::cout << time1.count() << " " << typeid(time1).name() << "\n";
    std::cout << time2.count() << " " << typeid(time2).name() << "\n";
    std::cout << time3.count() << " " << typeid(time3).name() << "\n";
    std::cout << time1 << "\n";
    std::cout << time2 << "\n";
    std::cout << time3 << "\n";
}

可能的输出：

1 NSt6chrono8durationIlSt5ratioILl1ELl1EEEE
2 NSt6chrono8durationIlSt5ratioILl60ELl1EEEE
7 NSt6chrono8durationIlSt5ratioILl1ELl1000EEEE
1s
2min
7ms