From: Oliver Scholz <alkibiades@gmx.de>
Subject: Re: New to elisp, learning by doing
Date: Tue, 18 Feb 2003 11:26:26 +0100 [thread overview]
Message-ID: <u7kbxkhpp.fsf@ID-87814.user.dfncis.de> (raw)
In-Reply-To: 84of5bidgc.fsf@lucy.is.informatik.uni-duisburg.de
kai.grossjohann@uni-duisburg.de (Kai Großjohann) writes:
> Queues are not a standard Lisp datatype, I'm afraid. (Or is there an
> Emacs Lisp package for this?)
FWIW, I have the following lying around, which is stolen&adapted from
Norvig's "Paradigms of Artificial Intelligence Programming".
(defun rtfread-make-queue ()
"Return a new, empty queue."
(let ((queue (cons nil nil)))
(setcar queue queue)))
(defsubst rtfread-enqueue (elt queue)
"Put ELT to the end of QUEUE."
(setcar queue
(setcdr (car queue)
(cons elt nil))))
(defsubst rtfread-dequeue (queue)
"Pop the first element from the queue.
Returns the removed element."
(prog1 (pop (cdr queue))
(when (null (cdr queue))
(setcar queue queue))))
(defsubst rtfread-queue-contents (queue)
"Return the contents of QUEUE."
(cdr queue))
(defsubst rtfread-queue-front (queue)
"Return the first element of QUEUE."
(car (rtfread-queue-contents queue)))
(defsubst rtfread-empty-queue-p (queue)
"Return non-nil if QUEUE is an empty queue."
(null (rtfread-queue-contents queue)))
(defun rtfread-queue-nconc (queue list)
"Add the elements of LIST to the end of QUEUE."
(setcar queue
(last (setcdr (car queue) list))))
Oliver
--
30 Pluviôse an 211 de la Révolution
Liberté, Egalité, Fraternité!
next prev parent reply other threads:[~2003-02-18 10:26 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-16 22:45 New to elisp, learning by doing John Rabkin
2003-02-17 2:03 ` Christopher J. White
2003-02-17 7:16 ` Kai Großjohann
2003-02-17 9:27 ` Hannu Koivisto
2003-02-18 8:02 ` Kai Großjohann
2003-02-17 18:24 ` Ehud Karni
[not found] ` <mailman.2034.1045507046.21513.help-gnu-emacs@gnu.org>
2003-02-17 19:50 ` Kai Großjohann
2003-02-18 10:26 ` Oliver Scholz [this message]
2003-02-17 18:47 ` Kevin Rodgers
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