C++中的Round()在哪里？

double round(double x);
float round(float x);
long double round(long double x);

#include<iostream>
#include <cmath>

int main() {
    double num = 3.14159;
    double rounded_num = round(num);
    std::cout << "Rounded number: "<< rounded_num<< std::endl;
    return 0;
}

Rounded number: 3