anchor.diff:  (defun build-edge (e)
     (if (equal (length e) 4)
         (make-fst-edge
  -       :src (edge-source e)
  -       :input-symb (edge-input e)
  -       :output-symb (edge-output e))
  +       :src (nth 0 e)
  +       :input-symb (nth 1 e)
  +       :output-symb (nth 2 e)
  +       :dst (nth 3 e))
       (make-edge
  -     :src (edge-source e) 
  -     :symb (edge-symbol e) 
  -     :dst (edge-destination e))))
  +     :src (nth 0 e) 
  +     :symb (nth 1 e) 
  +     :dst (nth 2 e))))
   
   ;;; This function returns the source state identification
   ;;; of this edge.
  -(defmethod edge-source (e)
  +(defmethod edge-source ((e cons))
     (nth 0 e))
   
   ;;; This function returns the source state identification
  
positive.code: 	    (string (edge-symbol edge)))
  	(edge-destination edge)))
  
  ;;; This function returns the destination state identification
  ;;; of this edge.
  (defmethod edge-destination ((e edge))
    (edge-dst e))
  
negative.code: 
  ;;; This function returns the symbol (input/output) of the edge
  (defmethod edge-symbol ((e fst-edge))
    (format nil "~A/~A" (fst-edge-input-symb e) (fst-edge-output-symb e)))
  
  (defmethod edge-input ((edge fst-edge))
    (fst-edge-input-symb edge))
  
  (defmethod edge-input ((edge edge))
    (edge-symbol edge))
  
  (defmethod edge-input ((edge cons))
    (edge-symbol (build-edge edge)))
  
  (defmethod edge-output ((edge fst-edge))
    (fst-edge-output-symb edge))
  
  (defmethod edge-output ((edge edge))
    (edge-symbol edge))
  
  (defmethod edge-output ((edge cons))
    (edge-symbol (build-edge edge)))
  
  
  ;;; This function returns the destination state identification
  ;;; of this edge.
  (defmethod edge-destination ((e edge))
    (edge-dst e))
  
  ;;; This function returns the destination state identification
  ;;; of this edge.
  (defmethod edge-destination ((e fst-edge))
    (fst-edge-dst e))
  
  ;;; This function returns the destination state identification
  ;;; of this edge.
  (defmethod edge-destination ((e cons))
    (edge-destination (build-edge e)))
  
  
  (defun edgify (edge)
  