anchor.diff:  	    (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))
  
positive.code: (defmethod edge-source ((e edge))
    (edge-src e))
  
  ;;; This function returns the symbol of this edge.
  (defmethod edge-symbol (e)
    (nth 1 e))
  
  ;;; This function returns the symbol of this edge.
  (defmethod edge-symbol ((e edge))
  
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)
  