anchor.diff:             (setf (node-right h) (insert-node (node-right h) key value tree lessp)))
             (t
              (setf (node-value h) value)))
  +        
           (when (node-red-p (node-right h))
             (setf h (lean-left h)))
           h)))
  
positive.code:         (incf (tree-count tree))
          (make-node :key key :value value :color :red))
        (progn
          (when (and (node-red-p (node-left h))
                     (node-red-p (node-left (node-left h))))
            (setf h (split-four-node h)))
          (cond
            ((funcall lessp key (node-key h))
             (setf (node-left  h) (insert-node (node-left  h) key value tree lessp)))
  
negative.code:   (format t "~A~A~A+---- NIL~A~%" indentation bar *black* *normal*))
  
  (defmethod dump ((self node) &optional (indentation "") (bar " "))
    (dump (node-left  self) (concat indentation bar "    ") "|")
    (format t "~A~A    |~%" indentation bar)
    (format t "~A~A~A+---- ~A: ~A~A~%" indentation bar
            (if (node-red-p self) *red* *black*) 
            (node-key self) (node-value self)
            *normal*)
    (format t "~A~A    |~%" indentation bar)
    (dump (node-right self) (concat indentation bar "    ") "|"))
  
  
  (defmethod dump ((self tree) &optional (indentation "") (bar " "))
  