检查C++中的double(或float)是否为NaN

#include<iostream>
#include <cmath>

int main() {
    double num = 0.0 / 0.0; // 计算一个NaN值

    if (std::isnan(num)) {
        std::cout << "The number is NaN."<< std::endl;
    } else {
        std::cout << "The number is not NaN."<< std::endl;
    }

    return 0;
}