Function ccw

contents/graham_scan/code/c/graham.c:24–26

}

double ccw(struct point a, struct point b, struct point c) {
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}

double polar_angle(struct point origin, struct point p) {
    return atan2(p.y - origin.y, p.x - origin.x);