anchor.diff:  		     (transformation-error-rect self)
   		     (transformation-error-transformation self)))))
   
  -(defmethod transformation-equal ((transformation1 standard-transformation) (transformation2 standard-transformation))
  +(defmethod transformation-equal ((transformation1 standard-transformation) 
  +                                 (transformation2 standard-transformation))
     (every #'coordinate=
            (multiple-value-list (get-transformation transformation1))
            (multiple-value-list (get-transformation transformation2))))
  
positive.code:             :initform nil
              :documentation "Cached inverse transformation.") ))
  
  
  #+:DEBUG
  (defmethod initialize-instance :after ((self standard-transformation) args)
    (declare (ignorable self args)) )
  
  (defmethod print-object ((self standard-transformation) sink)
    ;; printer
    (apply #'format sink "#<~S ~S ~S ~S ~S ~S ~S>"
           (type-of self)
           (multiple-value-list (get-transformation self))))
  
  (defun make-transformation (mxx mxy myx myy tx ty)
    ;; Make a transformation, which will map a point (x,y) into
  
negative.code: ;;;;  Transformations
  ;;;;
  
  (define-protocol-class transformation ())
  
  (defclass standard-transformation (transformation)
    ((mxx :type coordinate)
  