From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Francis Moreau Newsgroups: gmane.emacs.help Subject: Re: Basic questions about elisp Date: Thu, 5 Nov 2009 06:29:03 -0800 (PST) Organization: http://groups.google.com Message-ID: <258bd70d-d192-4007-8ebe-754724d6899c@m16g2000yqc.googlegroups.com> References: <1e9f8449-09ec-4a84-a332-9f05fadb8aa3@z41g2000yqz.googlegroups.com> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1257432180 5048 80.91.229.12 (5 Nov 2009 14:43:00 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 5 Nov 2009 14:43:00 +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 05 15:42:53 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 1N63Xz-0002h8-6A for geh-help-gnu-emacs@m.gmane.org; Thu, 05 Nov 2009 15:42:47 +0100 Original-Received: from localhost ([127.0.0.1]:40260 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N63Xt-0008PM-In for geh-help-gnu-emacs@m.gmane.org; Thu, 05 Nov 2009 09:42:41 -0500 Original-Path: news.stanford.edu!usenet.stanford.edu!postnews.google.com!m16g2000yqc.googlegroups.com!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 52 Original-NNTP-Posting-Host: 213.41.232.205 Original-X-Trace: posting.google.com 1257431343 8660 127.0.0.1 (5 Nov 2009 14:29:03 GMT) Original-X-Complaints-To: groups-abuse@google.com Original-NNTP-Posting-Date: Thu, 5 Nov 2009 14:29:03 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: m16g2000yqc.googlegroups.com; posting-host=213.41.232.205; posting-account=ekTE0goAAADiVCThPmo4ph0C5bTUhQOx User-Agent: G2/1.0 X-HTTP-Via: 1.1 grimoire.wyplay.int:3128 (squid/2.5.STABLE14) X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.11) Gecko/2009061118 Fedora/3.0.11-1.fc9 Firefox/3.0.11, gzip(gfe), gzip(gfe) Original-Xref: news.stanford.edu gnu.emacs.help:174420 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:69495 Archived-At: On Nov 5, 1:57=A0pm, to...@tuxteam.de wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > > On Thu, Nov 05, 2009 at 03:13:32AM -0800, Francis Moreau wrote: > > Hello, > > > I'm trying to learn elisp and have a couple of basic questions. > > > I'm iterating over a list using dotimes, but in the body of dotimes, > > the list can mutate. For example I have: > > > =A0 (dolist (elt lst) > > =A0 =A0 ;; some codes > > =A0 =A0 (nconc lst '(2))) > > > This adds/appends a new element to 'lst' list. It looks like 'dotimes' > > doesn't like it. > > > So I eventually wrote it like this > > > =A0 =A0 (setq i 0) > > =A0 =A0 (while (< i (length lst)) > > =A0 =A0 =A0 =A0 =A0 ;; some codes > > =A0 =A0 =A0 =A0 =A0 (x-nconc lst '(2)))) > > =A0 =A0 =A0 (setq i (1+ i))) > > > which is a bit ugly, is there another way to do that ? > > What about: > > =A0 (let ((l lst)) > =A0 =A0 (while l > =A0 =A0 =A0 (do-something-with (car l)) > =A0 =A0 =A0 (setq l (cdr l)))) > looks better but as David pointed out, appending something to a list is quite expensive. > This should be fine as long as you only append to lst. Dragons might > emerge whenever you do more drastic things to it ;-) > > (and you would have to re-think things when Emacs Lisp becomes > multi-threaded. It might work then and it might not). > Is this going to happen ? Thanks