anchor.diff:  (defmethod draw-location-info ((info immediate-input) stream)
     (when (null (gethash info *instruction-table*))
       (setf (gethash info *instruction-table*) (gensym))
  +    (format stream "   ~a [shape = ellipse, style = filled, fillcolor = green]~%"
  +	    (gethash info *instruction-table*))
  +    (format stream "   ~a [label = \"~a\"]~%"
  +	    (gethash info *instruction-table*)
  +	    (value info))))
  +
  +(defmethod draw-location-info ((info external-input) stream)
  +  (when (null (gethash info *instruction-table*))
  +    (setf (gethash info *instruction-table*) (gensym))
       (format stream "   ~a [shape = ellipse, style = filled, fillcolor = pink]~%"
   	    (gethash info *instruction-table*))
  -    (format stream "   ~a label = \"~a\"]~%"
  +    (format stream "   ~a [label = \"~a\"]~%"
   	    (gethash info *instruction-table*)
   	    (value info))))
   
  
positive.code: 
  (defun make-immediate-input (value)
    (make-instance 'immediate-input
      :value value))
  
  (defclass instruction ()
  
negative.code:     (format stream "  ~a [shape = box, label = \"~a\"]~%" 
  	    (gethash info *instruction-table*)
  	    (sicl-env:name (sicl-env:location info)))
      (format stream "  ~a -> ~a [color = blue]~%"
  	    (gethash info *instruction-table*)
  	    (gethash (sicl-env:location info) *instruction-table*))))
  
  