Function reflect

code/geometry/primitives.cpp:11–13

             P(about) = point(0,0)) {
  return (p - about) * exp(point(0, radians)) + about; }
point reflect(P(p), L(about1, about2)) {
  point z = p - about1, w = about2 - about1;
  return conj(z / w) * w + about1; }
point proj(P(u), P(v)) { return dot(u, v) / dot(u, u) * u; }
point normalize(P(p), double k = 1.0) {
  return abs(p) == 0 ? point(0,0) : p / abs(p) * k; }