anchor.diff:            (setf (last-access binding) (local-time:now))
             (setf (gethash owner (bindings node))
                   (make-instance 'binding))))
  -    (cl-custom-hash-table:with-custom-hash-table
  -      (pushnew node (gethash (entry node) (entries history))))
       (values history node)))
   
   (defmethod visit-all ((history history-tree) node)
  
positive.code:              (setf (value (entry node)) data)
               (let ((maybe-new-entry (add-entry history data)))
                 (push (setf node (make-node :entry maybe-new-entry
                                             :parent (current owner)))
                       (children (current owner)))))
           (let ((binding (gethash owner (bindings (current owner)))))
             (setf (forward-child binding) node))
  
negative.code:       (root (parent node))
        node))
  
  (defun make-node (&key parent entry history)
    (let ((node (make-instance 'node :parent parent :entry entry)))
      (cl-custom-hash-table:with-custom-hash-table
        (pushnew node (gethash (entry node) (entries history))))
      node))
  
  (define-class binding ()
    ((forward-child  nil
  