Function 添加两个分数和 output 十进制只给出 0

Question

I'm trying to make a simple program which adds two fractions. It takes four numbers as inputs: numerator and denominator of the first fraction and numerator and denominator of the second fraction. The output should be the sum of the two fractions in decimal form. My program isn't working and I'm stuck with how to fix it. It outputs 0.000 for all of the examples tried to run the function.

# include <stdio.h>

int fracsum(float n1, float d1, float n2, float d2)
{
    float n3, d3;
    double res;
    n3 = (n1*d2) + (d1*n2);
    d3 = d1 * d2;
    res = n3 / d3;
    return res;
}

int main(void)
{
    printf("%.3f %.3f %.3f\n",
       fracsum(1,2,2,4),
       fracsum(1,4,1,8),
       fracsum(4,3,5,6));

    return 0;
}

The output of this code is: 0.000 0.000 0.000

Answer 1

int fracsum

but you clearly want

double fracsum

from your printf call