Modulus of double

#include<iostream>
using namespace std;

double find_mod(double a, double b){
    if(a < 0) a = -a;
    if(b < 0) b = -b;

    double mod = a;
    while(mod >= b){
        mod = mod - b;
    }
    if(a < 0){
        mod = -mod;
    }
    return mod;
}

int main(){
    int t; cin >> t;
    while(t--){
        double a, b;
        cin >> a >> b;
        cout << find_mod(a, b) << endl;
    }
}