Question

int* difference (int *a, int *b){
    if (*a > *b){
    *a = *a - *b;
    }else{
        *a = *b - *a;
    }
    return a;
}

int main (){
    int *xp, *yp;
    int x, y;

    x = 9;
    y = 7;

    xp = &x;
    yp = &y;

    xp = difference (xp,yp);
    printf("xp value: %d\n", *xp);

    return 0;
}

For some reasons I need my program to do some mathematical operations on mono dimensional arrays. I posted a sample here because I’m concerned regarding the difference function and its returned value.

The both values are pointers but I need to do this because I can’t know for sure which of the values is grater. Is my way of doing things a good practice or is there a better way for this issue?

Answer 1

Personally, i try to avoid pointers as possible or, if not, always check null pointers. In this case, I would modify difference() by:

int difference (int a, int b){
    if (a > b){
       return a - b:
    return b - a;
}

With this new way, you doesn’t need to check null values:

int* difference (int *a, int *b){
    if (a && b)
    {
        if (*a > *b){
           *a = *a - *b;
        }else{
           *a = *b - *a;
        }
        return a;
    }

    // and what must I do with null pointers???????
}

Besides, in main function, you doesn’t need to create pointers from int:

int main (){
    int x, y;

    x = 9;
    y = 7;

    x = sum (x, y);
    printf("xp value: %d\n", x);

    return 0;
}

In resume, try to avoid pointers if not necessary or, if not, always check null values