anchor.diff:          radius-2-dx (coerce radius-2-dx 'coordinate)
           radius-2-dy (coerce radius-2-dy 'coordinate)
           start-angle (and start-angle (coerce start-angle 'coordinate))
  -        end-angle (and start-angle (coerce start-angle 'coordinate)) )
  +        end-angle (and end-angle (coerce end-angle 'coordinate)) )
   
     (let ((tr (make-3-point-transformation* 0 0 1 0 0 1
                                             center-x center-y
  
positive.code: 
  (defclass bounding-rectangle () ())
  
  (defclass region (#|ink|#) ())
  (defclass path (region bounding-rectangle) ())
  (defclass area (region bounding-rectangle) ())
  (defclass region-set  (region bounding-rectangle) ())
  
negative.code:    (tr          :initarg :tr)))         ;a transformation from the unit circle to get the elliptical object
  
  (defclass standard-ellipse (ellipse elliptical-thing) ())
  (defclass standard-elliptical-arc (elliptical-arc elliptical-thing) ())
  
  (defun ellipsep (object)
    (typep object 'ellipse))
  