anchor.diff:            (setf (parent lefrig) n))
         (cond ((null par) (setf (root tree) lef))
               ((eql n (right par)) (setf (right par) lef))
  -            (T (setf (left par) lef)))))
  +            (T (setf (left par) lef))))
     T
   )
   
  
positive.code:   (princ "done.")
    (terpri)
  
    (princ "Does the tree contain '-42'? -> ")
    (if (contains tree -42)
        (princ "Yes")
  
negative.code:              The node to rotate over, which should not be {@code null}.
      @param deletion
               Indicator if this is a rotation after an insertion or after
               a deletion of the node."
  
    (if (and
         (eql (root tree) n)
  