anchor.diff:             :documentation "The key is an owner identifier (an artitrary balue),
   the value is an `owner'.")
      (current-owner-identifier (error "Owner identifier required")
  -                  :reader current-owner-identifier
  -                  :type t
  -                  :export t
  -                  :documentation "Must be one of the `owners' keys.")
  +                             :reader current-owner-identifier
  +                             :type t
  +                             :export t
  +                             :documentation "Must be one of the `owners' keys.")
      (entries (make-entry-hash-table)
               :type hash-table
               :documentation "The key is an `entry', the value is the list of
   nodes that hold this data.")
      (key #'identity
  -              :type function
  -              :documentation "The result of this function is passed to `test'
  +        :type function
  +        :documentation "The result of this function is passed to `test'
   and `hash-function'.  It is useful to uniquely identify (i.e. avoid
   duplications) objects from one of their slots.")
      (test #'equalp
  
positive.code: over two entries are equal.
  Also see `hash-function'.")
     (hash-function #'sxhash
           :type function
           :documentation "Function that returns the hash of the result of `key'
  called over an `entry'.
  Also see `test'."))
    (:export-class-name-p t)
    (:export-accessor-names-p t)
  
negative.code:   (:accessor-name-transformer #'class*:name-identity)
    (:documentation "Internal node of the history tree."))
  
  (export 'value)
  (defmethod value ((node node))
    (value (entry node)))
  
  