anchor.diff:  (defun make-scaling-transformation* (scale-x scale-y &optional origin-x origin-y)
     (let ((origin-x (or origin-x 0))
           (origin-y (or origin-y 0)))
  -    (make-transformation scale-x 0 0 scale-y (- origin-x (* scale-x origin-x)) (- origin-y (* scale-y origin-y)))) )
  +    (make-transformation scale-x 0
  +                         0 scale-y
  +                         (- origin-x (* scale-x origin-x)) (- origin-y (* scale-y origin-y)))) )
   
   (defun make-reflection-transformation (point1 point2)
     (make-reflection-transformation* (point-x point1) (point-y point1) (point-x point2) (point-y point2)))
  
positive.code:   ;; Make a transformation, which will map a point (x,y) into
    ;;  x' = mxx*x + mxy*y + tx
    ;;  y' = myx*x + myy*y + ty
    (let ((res (make-instance 'standard-transformation)))
      (setf (slot-value res 'mxx) (coerce mxx 'coordinate)
            (slot-value res 'mxy) (coerce mxy 'coordinate)
            (slot-value res 'myx) (coerce myx 'coordinate)
            (slot-value res 'myy) (coerce myy 'coordinate)
            (slot-value res 'tx)  (coerce tx 'coordinate)
            (slot-value res 'ty)  (coerce ty 'coordinate))
      res))
  
  (defmethod get-transformation ((self standard-transformation))
    ;; Get the values of the transformation matrix as multiple values.
    ;; This is not an exported function!
    (with-slots (mxx mxy myx myy tx ty) self
      (values mxx mxy myx myy tx ty)))
  
  (defun make-translation-transformation (translation-x translation-y)
    (make-transformation 1 0 0 1 translation-x translation-y))
  
  (defun make-rotation-transformation (angle &optional origin)
    (if origin
  
negative.code:          (multiple-value-list (get-transformation transformation1))
           (multiple-value-list (get-transformation transformation2))))
  
  ;; make-transformation always returns +identity-transformation+, if
  ;; the transformation to be build would be the identity. So we
  ;; IDENTITY-TRANSFORMATION-P can just specialize on
  ;; STANDARD-IDENTITY-TRANSFORMATION.
  
  (defmethod identity-transformation-p ((transformation standard-identity-transformation))
    t)
  
  (defmethod identity-transformation-p ((transformation standard-transformation))
    nil)
  
  ;; Same for translations, but +identity-transformation+ is a translation too.
  
  (defmethod translation-transformation-p ((transformation standard-translation))
    t)
  
  (defmethod translation-transformation-p ((transformation standard-identity-transformation))
    t)
  
  (defmethod translation-transformation-p ((transformation standard-transformation))
    nil)
  
  (defun transformation-determinant (tr)
    (multiple-value-bind (mxx mxy myx myy) (get-transformation tr)
  