anchor.diff:                                 (garden (living-room east door))
                                  (attic (living-room downstairs ladder))))
   
  +
  +(defparameter *max-label-length* 30)
  +
   ;; * generating the dot information
   
   
  
positive.code:             (lambda ()
                (ugraph->dot nodes edges))))
  
  (ugraph->png "wizard-graph-undirected.dot"
               *wizard-nodes*
               *wizard-edges*)
  
  ;; maplist iterating by cdr
  ;; maplist itearting by car
  ;; map needs a selector
  (mapcar #'print '(a b c))
  ;; =>
  ;; A
  ;; B
  ;; C
  
  (maplist #'print '(a b c))
  ;; (A B C)
  ;; (B C)
  ;; (C)
  
negative.code:                 (cdr node)))
          edges))
  
  
  (defun graph->dot (nodes edges)
    (princ "digraph{")
    (nodes->dot nodes)
    (edges->dot edges)
    (princ "}"))
  
  
  (defun dot->png (fname thunk)
  