void squares_change(double a[], unsigned int alen) {
    unsigned int i;

    for (i = 0; i < alen; i++) {
        a[i] *= a[i];
    }
}

void bar() {
    double xs[] = {1, 2, 3};
    squares_change(xs, 3);
    // xs is now 1, 4, 9
}