anchor.diff:  
   (defparameter *location* 'living-room)
   
  +(defparameter *allowed-commands* '(look walk pickup inventory))
  +
   (defun describe-location (location nodes)
     (cadr (assoc location nodes)))
   
  
positive.code: (defun describe-objects (loc objs obj-loc)
    (labels ((describe-obj (obj)
  	     `(you see a ,obj on the floor.)))
      (apply #'append (mapcar #'describe-obj (object-at loc objs obj-loc)))))
  
  (defun look ()
    (append (describe-location *location* *nodes*)
  
negative.code: 	       (look))
  	'(you cannot go that way.))))
  
  (defun pickup (object)
    (cond ((member object (objects-at *location* *objects* *object-locations*))
  	 (push (list object 'body) *object-locations*)
  	 `(you are now carrying the ,object))
  