Peter Lewerin <peter.lewerin@swipnet.se> wrote:
+---------------
| peter.lewerin@swipnet.se (Peter Lewerin) wrote
| > Of course.  With this added requirement, a tail slot makes sense:
| 
| Ooops.  Forgot to null the tail slot when the last element is
| dequeued.  (Actually, it doesn't matter, but anyway.)
| 
|     (defmethod dequeue :after ((q constant-time-fifo))
|       (with-slots (contents tail) q
|         (unless contents
|           (setf tail nil))))
+---------------

Alternatively, you could just as easily do that right
in the primary method itself:

    (defmethod dequeue ((q constant-time-fifo))
      (with-slots (contents tail) q
	(prog1
	 (pop contents)
	 (unless contents
	   (setf tail nil)))))

That way, somebody reading your code doesn't have to
go looking for the :AFTER method. [Plus, it's likely
to be somewhat faster as well.]

Note: I don't have anything against :AFTER methods in
general, but it seems a bit excessive in this case.


-Rob

-----
Rob Warnock			<rpw3@rpw3.org>
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