Function ccw

contents/graham_scan/code/cpp/graham_scan.cpp:18–20

}

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

double polar_angle(const point& origin, const point& p) {
  return std::atan2(p.y - origin.y, p.x - origin.x);