anchor.diff:  should return non-nil.")
      (current nil
               :type (or null node)
  -            :initform nil
               :documentation "The current node.
  -It's updated every time a node is visited."))
  +It's updated every time a node is visited.")
  +   (nodes '()
  +          :type (or null (cons node))
  +          :documentation "The list of owned nodes."))
     (:export-class-name-p t)
     (:export-accessor-names-p t)
     (:accessor-name-transformer #'class*:name-identity)
  
positive.code:   "Go COUNT parent up from the current OWNER node.
  Return (values OWNER (current OWNER)) so that `back' and `forward' calls can
  be chained."
    (check-type count 'positive-integer)
    (when (and (current owner)
               (parent (current history)))
      (let ((former-current (current owner)))
        (visit owner (parent (current owner)))
        ;; Put former current node back as forward-child if it is not already
  
negative.code:   "Go COUNT first-children down from the current OWNER node.
  Return (values OWNER (CURRENT OWNER)) so that `back' and `forward' calls can be
  chained."
    (check-type count positive-integer)
    (when (and (current owner)
               (children (current owner)))
      (visit (forward-child (current-binding owner)))
  