anchor.diff:         :do (setf (sas-cursor-value dst) (sas-cursor-value src))
          :finally (return copy))))
   
  -(defmethod elt ((self sequential-access-sequence) index)
  +(define-method elt ((self sequential-access-sequence) index)
     (check-type index (integer 0))
     (loop
        :for cursor = (sas-head self) :then (sas-cursor-next cursor)
  
positive.code:        :finally (return copy))))
  
  ;;; primitives:
  ;;; (defmethod elt ((self direct-access-sequence) index) )
  ;;; (defmethod (setf elt) (value (self direct-access-sequence) index)   value)
  
  
  ;;;---------------------------------------------------------------------
  
negative.code:                                            &key (key nil)))
  
  
  (define-method make-sequence ((result-type sequence) size &key initial-element)
    (declare (ignore result-type size initial-element))
    (not-implemented-yet  make-sequence))
  
  
  (dolist (name '(remove delete))
  