From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: cl-dolist, dolist, cl-return, Date: Wed, 08 Jul 2015 10:44:13 -0400 Message-ID: References: <87fv4za4jo.fsf@nl106-137-147.student.uu.se> <87k2ub2bgb.fsf@nl106-137-147.student.uu.se> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1436366687 30353 80.91.229.3 (8 Jul 2015 14:44:47 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 8 Jul 2015 14:44:47 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Wed Jul 08 16:44:47 2015 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZCqac-0002Yn-3H for geh-help-gnu-emacs@m.gmane.org; Wed, 08 Jul 2015 16:44:46 +0200 Original-Received: from localhost ([::1]:35457 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZCqab-0004Mw-JA for geh-help-gnu-emacs@m.gmane.org; Wed, 08 Jul 2015 10:44:45 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:37478) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZCqaI-0004Jz-1a for help-gnu-emacs@gnu.org; Wed, 08 Jul 2015 10:44:26 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZCqaE-0002nT-PW for help-gnu-emacs@gnu.org; Wed, 08 Jul 2015 10:44:25 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:51142) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZCqaE-0002m6-Io for help-gnu-emacs@gnu.org; Wed, 08 Jul 2015 10:44:22 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZCqaC-0002HN-H3 for help-gnu-emacs@gnu.org; Wed, 08 Jul 2015 16:44:20 +0200 Original-Received: from 157-52-6-103.cpe.teksavvy.com ([157-52-6-103.cpe.teksavvy.com]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 08 Jul 2015 16:44:20 +0200 Original-Received: from monnier by 157-52-6-103.cpe.teksavvy.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 08 Jul 2015 16:44:20 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 15 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: 157-52-6-103.cpe.teksavvy.com User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:LkNh0N1mAqXju4k+BN+vdWe1vuY= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:105528 Archived-At: >> Right, the question often makes sense for loop boundary computations, >> but for this specific case, if you think enough about it, it makes no >> sense to re-evaluate it: you'd have to use an index into the list, >> and at each iteration, increment the index, recompute the list, and >> do an (nth ), which would overall be >> *really* inefficient. > No, of course I don't want to re-evaluate it! I didn't My point was that the re-evaluation part would be just a side-problem: even if your expression is a mere variable (so re-evaluating it is very cheap), the need to use `nth' at each step would force an O(N^2) complexity to this loop. Stefan