anchor.diff:       (setf (get ',var 'editor-variable)
              (make-editor-variable :value ,value
                                    :documentation ,documentation
  -                                 :local-indicator (gensym ,(string var))))
  +                                 :local-indicator (gensym ,(string var))
  +                                 :change-value-hook ,change-value-hook))
        t))
   
   (defun editor-variable-error (symbol)
  
positive.code:                     (editor-variable-local-indicator
                       (get symbol 'editor-variable)))))
  
  (defmacro define-editor-variable (var &optional value documentation)
    (check-type var symbol)
    `(unless (get ',var 'editor-variable)
       (defvar ,var)
  
negative.code:                              (editor-variable-local-indicator var))
                 value)))
        ((:global)
         (let ((fn (editor-variable-change-value-hook var)))
           (when fn
             (funcall fn value)))
         (setf (editor-variable-value var) value)))))
  
  (defun variable-documentation (symbol)
  