anchor.diff:  ;;; implementation, a common AI planning problem. The monkey's objective is to
   ;;; find and eat some bananas.
   
  -;;; $Id: mab-clos.lisp,v 1.6 2001/05/24 19:55:45 youngde Exp $
  +;;; $Id: mab-clos.lisp,v 1.7 2001/05/31 19:13:56 youngde Exp $
   
   (in-package "LISA-USER")
   
   (use-default-engine)
   
  -(defclass monkey ()
  +(defclass mab-fundamental () ())
  +
  +(defclass monkey (mab-fundamental)
     ((location :initarg :location
                :initform 'green-couch)
      (on-top-of :initarg :on-top-of
  
positive.code:   (monkey (satisfied t) (:object ?monkey))
    =>
    (format t "Monkey is satisfied: ~S~%" ?monkey))
  
  ;;; startup rule...
  
  
negative.code:    (holding :initarg :holding
              :initform 'nothing)))
  
  (defclass thing (mab-fundamental)
    ((name :initarg :name)
     (location :initarg :location)
     (on-top-of :initarg :on-top-of
  