Thread: call-by-reference wrong output

Hi,

i hope someone can help me... i coded the this function:

Code:

#include <stdio.h>
#include <math.h>


struct parabel {
    double a;
    double b;
    double c;
};


int scheitelhoehe(struct parabel p, double *y) {
    int tmp;
    int a1 = 0, b1 = 0, c1 = 0;
    a1 = 1; 
    b1 = 2; 
    c1 = 3;
    tmp = 0;


    if (a1 != 0)
    {
        tmp = -(b1 / (2 * a1));
        *y = a1*pow(tmp, 2) + (b1*tmp) + c1;
        return 0;
    }
    else
    {
        return 1;
    }
}

int main() {
    struct parabel p[] = {
            { 1, 2, 3 },
    };
    double y = 0;
    scheitelhoehe(p[0], &y);
    printf("y = %d\n", y);
}

can somebody tell me why the output is 'y = 0' and not 'y = 2'?
thank you sooooo much!

kongkong

Originally Posted by laserlight

Since y is a double, you should use %f rather than %d with printf:

Code:

printf("y = %f\n", y);

Thank you very much, shame on me for not seeing that obvious little bastard.