(defun serialize-common (object transaction-log fn)
  (with-accessors ((object-id-table object-id-table)
                   (next-object-id next-object-id)
                   (log-stream log-stream))
      transaction-log
    (let ((id (gethash object object-id-table)))
      (if (null id)
          (progn
            (setf id (incf next-object-id))
            (setf (gethash object object-id-table) id)
	    (funcall fn object id log-stream transaction-log))
          (format log-stream "#~d^" id)))))

(defmacro with-serialize-common ((object transaction-log id log-stream) &body body)
  `(serialize-common
    object
    transaction-log
    (lambda (,object ,id ,log-stream ,transaction-log)
      ,@body)))

(defmethod serialize ((object cons) transaction-log)
  (with-serialize-common (object transaction-log id log-stream)
    (format log-stream "#~d!(" id)
    (serialize (car object) transaction-log)
    (format log-stream " . ")
    (serialize (cdr object) transaction-log)
    (format log-stream ")")))

(with-output-to-string (output-stream)
  (let ((transaction-log (make-transaction-log output-stream (make-hash-table))))
    (serialize (cons 'a 'b) transaction-log)))
;;; "#2!(CLOBBER::A . CLOBBER::B)"