From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.help Subject: Re: `looking-back' strange warning Date: Fri, 02 Oct 2015 03:19:03 +0200 Message-ID: <87612q6pa0.fsf@web.de> References: <560B9C7F.2060301@easy-emacs.de> <560CD7CE.4010404@yandex.ru> <6524c81a-949c-40d1-b990-d214d6ee5b60@default> <560D73DF.8040403@yandex.ru> <560D7A68.8040404@easy-emacs.de> <560D8289.6010409@yandex.ru> <560D8F96.5040200@easy-emacs.de> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1443748840 12657 80.91.229.3 (2 Oct 2015 01:20:40 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 2 Oct 2015 01:20:40 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Oct 02 03:20:31 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 1Zhp1R-00051z-Lc for geh-help-gnu-emacs@m.gmane.org; Fri, 02 Oct 2015 03:20:29 +0200 Original-Received: from localhost ([::1]:56928 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zhp1R-0001Oa-78 for geh-help-gnu-emacs@m.gmane.org; Thu, 01 Oct 2015 21:20:29 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:44981) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zhp19-0001LI-JX for help-gnu-emacs@gnu.org; Thu, 01 Oct 2015 21:20:12 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zhp14-0003Ob-KT for help-gnu-emacs@gnu.org; Thu, 01 Oct 2015 21:20:11 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:53068) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zhp14-0003N4-En for help-gnu-emacs@gnu.org; Thu, 01 Oct 2015 21:20:06 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1Zhp12-0004ZV-D1 for help-gnu-emacs@gnu.org; Fri, 02 Oct 2015 03:20:04 +0200 Original-Received: from ip-90-186-3-61.web.vodafone.de ([90.186.3.61]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 02 Oct 2015 03:20:04 +0200 Original-Received: from michael_heerdegen by ip-90-186-3-61.web.vodafone.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 02 Oct 2015 03:20:04 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 24 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: ip-90-186-3-61.web.vodafone.de User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:ZEjpgpBiuMvVmms05MzLpzItOH8= 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:107450 Archived-At: Stefan Monnier writes: > You can pass (point-min) for the limit if that's what you want. > Making it optional Encourages people to think that looking-at is just > like looking-back, with the same performance characteristic, whereas > making it mandatory encourages people to put a reasonable limit and > hence avoid pathological behavior at the end of large buffers. My two cents: Even if you specify an optimal limit, `looking-back' can still be unnecessarily slow. For example, (looking-back "xy" 2) is much slower than (and (> (point) 2) (save-excursion (goto-char (- (point) 2)) (looking-at "xy"))) where "xy" stands for any plain string. Michael.