srecord DoubleEdge(DoublePt a, DoublePt b) {
  *(double x1, double y1, double x2, double y2) {
    a = DoublePt(x1, y1);
    b = DoublePt(x2, y2);
  }
  
  DoublePt a() { ret a; }
  DoublePt b() { ret b; }
  
  double x1() { ret a.x; }
  double y1() { ret a.y; }
  double x2() { ret b.x; }
  double y2() { ret b.y; }
}