anchor.diff:        (read-token stream)
       (if donep
           token
  -        (parse-token token))))
  +        (when token
  +          (parse-token token)))))
  
positive.code:      do (if (char= end-char char)
              (progn (read-char stream nil nil)
                     (return-from clutter-read-delimited-list (nreverse list)))
              (progn #+nil(read-char stream nil nil)
                     (push (clutter-read stream) list)))))
  
  (set-clutter-reader-macro-function #\( (lambda (stream char)
                                           (declare (ignore char))
  
negative.code:                     (return-from read-token (values (car result) t)))))
              (progn (vector-push-extend char token)
                     (setf collecting-token t)))
       finally (if collecting-token
                   (return token)
                   nil)))
  
  (defun parse-token (token)
    (or (parse-integer-token token)
  