anchor.diff:  
   
   
  -(defclass singleton-class (standard-class)
  +(defclass singleton (standard-class)
     ())
   
   
  -(validate-class singleton-class)
  +(validate-class singleton)
   
   
   (defclass singleton-slot-definition (standard-slot-definition)
  
positive.code: 
  (defclass singleton-2 (singleton-1)
    ((sl-c))
    (:metaclass singleton-class))
  
  (finalize-inheritance (find-class 'singleton-2))
  
  
negative.code:   ())
  
  
  (defmethod effective-slot-definition-class ((class singleton)
                                              &rest initargs)
    (find-class 'singleton-effective-slot-definition))
  
  