anchor.diff:      (setf (slot-contents slots location) new-value)))
   
   (defun std-slot-value (instance slot-name)
  +  (when (not (symbolp slot-name))
  +    (setf slot-name (slot-definition-name slot-name)))
     (flet ((cached-location ()
              (let ((cache (slot-contents (std-instance-slots (class-of instance))
                                          *standard-class-slot-cache-position*)))
  
positive.code:         (t (slot-makunbound-using-class (class-of object) object slot-name))))
  
  (defun std-slot-exists-p (instance slot-name)
    (not (null (find slot-name (class-slots (class-of instance))
                     :key #'slot-definition-name))))
  (defun slot-exists-p (object slot-name)
  
negative.code:   (std-slot-boundp instance slot-name))
  (defmethod slot-boundp-using-class
             ((class funcallable-standard-class) instance slot-name)
    (fc-std-slot-boundp instance slot-name))
  
  (defgeneric slot-makunbound-using-class (class instance slot-name))
  (defmethod slot-makunbound-using-class
  