anchor.diff:  ;;;
   ;;; Class VARIABLE-ENTRY.
   
  -(defclass variable-entry (base-entry named-entry)
  +(defclass variable-entry (named-entry)
     (;; This slot contains true if and only if this entry represents a
      ;; constant variable.
      (%constantp :initform nil :accessor constantp)
  
positive.code: ;;; required, an instance of this class is created, and then never
  ;;; removed.
  
  (defclass function-entry (base-entry named-entry)
    (;; The value of this slot is a CONS cell in which the CAR is always
     ;; a function.  When the function is unbound, it contains the
     ;; function in the UNBOUND slot, which signals an error.
  
negative.code: 
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  ;;; NAMED-ENTRY.
  ;;; 
  ;;; A mixin class for entries having a name associated with them. 
  