From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Nick Dokos Newsgroups: gmane.emacs.help Subject: Re: How to count the number of occurrences of a character in a string? Date: Mon, 12 Oct 2015 19:27:43 -0400 Message-ID: <87d1wjy8eo.fsf@alphaville.usersys.redhat.com> References: <874mhvq3b2.fsf@mbork.pl> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1444692500 8330 80.91.229.3 (12 Oct 2015 23:28:20 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 12 Oct 2015 23:28:20 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue Oct 13 01:28:11 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 1ZlmVl-0007Ex-95 for geh-help-gnu-emacs@m.gmane.org; Tue, 13 Oct 2015 01:28:09 +0200 Original-Received: from localhost ([::1]:59279 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZlmVk-0005DQ-Dz for geh-help-gnu-emacs@m.gmane.org; Mon, 12 Oct 2015 19:28:08 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50161) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZlmVa-0005DF-79 for help-gnu-emacs@gnu.org; Mon, 12 Oct 2015 19:27:59 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZlmVV-0002vA-V1 for help-gnu-emacs@gnu.org; Mon, 12 Oct 2015 19:27:58 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:35517) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZlmVV-0002uv-Og for help-gnu-emacs@gnu.org; Mon, 12 Oct 2015 19:27:53 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZlmVS-0006w7-Jq for help-gnu-emacs@gnu.org; Tue, 13 Oct 2015 01:27:50 +0200 Original-Received: from nat-pool-bos-t.redhat.com ([66.187.233.206]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 13 Oct 2015 01:27:50 +0200 Original-Received: from ndokos by nat-pool-bos-t.redhat.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 13 Oct 2015 01:27:50 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 41 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: nat-pool-bos-t.redhat.com User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:UV5gTwfk88V7NwlHOWtBE9Kxv1k= 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:107598 Archived-At: Kaushal Modi writes: > I took it up as an elisp exercise and got the below (not sure if it is > performance optimal for your application): > > The catch form returns the number of matches. > > (let ((char ?a) > (str "abcda")) > (catch 'break > (let* ((str str) > (len (length str)) > (num-matches 0) > match-pos) > (dotimes (i len) > (setq match-pos (string-match-p (char-to-string char) str)) > (when match-pos > (setq str (substring-no-properties str (1+ match-pos))) > (setq len (length str)) > (setq num-matches (1+ num-matches))) > (when (= 0 len) > (throw 'break num-matches)))))) > What happens if len never becomes 0 in the loop? E.g looking for "f" in "falala" or "alala"? No throw, so catch returns nil: you probably want to add another throw outside the loop; or (better) do something else when match-pos is nil (there are no more matches), so you don't go through the loop uselessly: (if match-pos (progn (setq str ...) (setq len ...) (setq nm-matches)) (throw 'break num-matches)) But I suspect cl-count will be much faster. Nick