anchor.diff:  ;;; Drawing datum EXTERNAL-INPUT.
   
   (defmethod draw-datum ((datum external-input) stream)
  +  (format stream "  ~a [shape = ellipse, style = filled];~%"
  +	  (datum-id datum))
     (format stream "   ~a [fillcolor = pink, label = \"~a\"]~%"
   	  (datum-id datum) (value datum)))
   
  
positive.code: ;;; Drawing datum DYNAMIC-LOCATION.
  
  (defmethod draw-datum ((datum dynamic-location) stream)
    (format stream "   ~a [fillcolor = darkorchid, label = \"~a\"]~%"
  	  (datum-id datum) (index datum)))
  
  
negative.code: ;;; Drawing datum CONSTANT-INPUT.
  
  (defmethod draw-datum ((datum constant-input) stream)
    (format stream "  ~a [shape = ellipse, style = filled];~%"
  	  (datum-id datum))
    (format stream "   ~a [fillcolor = green, label = \"~a\"]~%"
  	  (datum-id datum) (value datum)))
  
  