How to output with 3 digits after the decimal point with C++ stream?

Question

Given a variable of float type, how to output it with 3 digits after the decimal point, using iostream in C++?

Answer 1

Use setf and precision.

#include <iostream>

using namespace std;

int main () {
    double f = 3.14159;
    cout.setf(ios::fixed,ios::floatfield);
    cout.precision(3);
    cout << f << endl;
    return 0;
}

This prints 3.142

Answer 2

This one does show "13.142"

#include <iostream>
#include <iomanip>
using namespace std;

int main(){
    double f = 13.14159;
    cout << fixed;
    cout << setprecision(3) << f << endl;
    return 0;
}