sclass DoublePt is IDoublePt {
  double x, y;
  
  *() {}
  *(Point p) {
    x = p.x;
    y = p.y;
  }
  *(double *x, double *y) {}
  
  equals DoublePt p { ret x == p.x && y == p.y; }
  public int hashCode() {
    ret boostHashCombine(main hashCode(x), main hashCode(y));
  }
  
  toString {
    ret x + ", " + y;
  }
  
  double length() { ret sqrt(x*x+y*y); }
  
  public double x_double() { ret x; }
  public double y_double() { ret y; }
}