From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Kevin Rodgers Newsgroups: gmane.emacs.help Subject: Re: LISP Questions - random, random elements and memory management Date: Wed, 18 Nov 2009 19:53:38 -0700 Message-ID: References: <20091118.075428.224836459.jeff@chaosphere.com> <20091118.080939.42107716.jeff@chaosphere.com> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1258599296 19325 80.91.229.12 (19 Nov 2009 02:54:56 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 19 Nov 2009 02:54:56 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Nov 19 03:54:51 2009 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1NAxAW-00041w-Ph for geh-help-gnu-emacs@m.gmane.org; Thu, 19 Nov 2009 03:54:49 +0100 Original-Received: from localhost ([127.0.0.1]:42121 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NAxAW-0005Lm-7s for geh-help-gnu-emacs@m.gmane.org; Wed, 18 Nov 2009 21:54:48 -0500 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NAx9t-0005Dm-42 for help-gnu-emacs@gnu.org; Wed, 18 Nov 2009 21:54:09 -0500 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NAx9o-0005Cw-CQ for help-gnu-emacs@gnu.org; Wed, 18 Nov 2009 21:54:08 -0500 Original-Received: from [199.232.76.173] (port=60632 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NAx9o-0005Cm-23 for help-gnu-emacs@gnu.org; Wed, 18 Nov 2009 21:54:04 -0500 Original-Received: from lo.gmane.org ([80.91.229.12]:48799) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NAx9n-0006R2-4o for help-gnu-emacs@gnu.org; Wed, 18 Nov 2009 21:54:03 -0500 Original-Received: from list by lo.gmane.org with local (Exim 4.50) id 1NAx9k-0003n6-OI for help-gnu-emacs@gnu.org; Thu, 19 Nov 2009 03:54:00 +0100 Original-Received: from c-71-237-24-138.hsd1.co.comcast.net ([71.237.24.138]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 19 Nov 2009 03:54:00 +0100 Original-Received: from kevin.d.rodgers by c-71-237-24-138.hsd1.co.comcast.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 19 Nov 2009 03:54:00 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 24 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: c-71-237-24-138.hsd1.co.comcast.net User-Agent: Thunderbird 2.0.0.23 (Macintosh/20090812) In-Reply-To: <20091118.080939.42107716.jeff@chaosphere.com> X-detected-operating-system: by monty-python.gnu.org: GNU/Linux 2.6 (newer, 3) X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:69894 Archived-At: Jeff Clough wrote: > From: Jeff Clough > Date: Wed, 18 Nov 2009 07:54:28 -0500 (EST) > >> (defun get-random-element (list) >> "Returns a random element of LIST." >> (if (not (and (list) (listp list))) >> (nth (random (1- (1+ (length list)))) list) >> (error "Argument to get-random-element not a list or the list is empty"))) >> > > Yay for not being awake! The above should be this: > > (defun get-random-element (list) > "Returns a random element of LIST." > (if (and list (listp list)) > (nth (random (1- (1+ (length list)))) list) > (error "Argument to get-random-element not a list or the list is empty"))) Is (1- (1+ (length list))) not exactly the same as (length list)? -- Kevin Rodgers Denver, Colorado, USA