From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Pascal Bourguignon Newsgroups: gmane.emacs.help Subject: Re: match-string debugging problem Date: 10 Mar 2005 18:06:52 +0100 Organization: [posted via Easynet Spain] Message-ID: <87ekenmnv7.fsf@thalassa.informatimago.com> References: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1110474758 14681 80.91.229.2 (10 Mar 2005 17:12:38 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 10 Mar 2005 17:12:38 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Mar 10 18:12:37 2005 Original-Received: from lists.gnu.org ([199.232.76.165]) by ciao.gmane.org with esmtp (Exim 4.43) id 1D9RAc-0005pF-O6 for geh-help-gnu-emacs@m.gmane.org; Thu, 10 Mar 2005 18:09:59 +0100 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1D9RPW-0002H4-Fb for geh-help-gnu-emacs@m.gmane.org; Thu, 10 Mar 2005 12:25:23 -0500 Original-Path: shelby.stanford.edu!newsfeed.stanford.edu!news.tele.dk!news.tele.dk!small.news.tele.dk!colt.net!easynet-quince!easynet.net!easynet-post2!not-for-mail Original-Newsgroups: gnu.emacs.help User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 Original-Lines: 60 Original-NNTP-Posting-Host: 62.93.174.79 Original-X-Trace: DXC=eKlILnPhVDTN6K9KK;\Q7ZEY<>`XO4V7]>Uh 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 X-MailScanner-To: geh-help-gnu-emacs@m.gmane.org Xref: news.gmane.org gmane.emacs.help:24741 X-Report-Spam: http://spam.gmane.org/gmane.emacs.help:24741 Stephen Berman writes: > There seems to be something about match-string that I don't > understand. Here is an example of the kind of code I'm working with: > > (defvar mystring1 "+++++ ") > (defvar mystring2 " ~~~~~") > (defun mystring-list () > (interactive) > (with-current-buffer (get-buffer-create "*test*") > (switch-to-buffer "*test*") > (dotimes (num 5) > (insert mystring1 "test" (int-to-string (1+ num)) mystring2 "\n")) > (goto-char (point-min)) > (let ((mystring-list ())) > (while (re-search-forward > (concat "^" (regexp-quote mystring1) "\\(.+\\)" > (regexp-quote mystring2) "$") > (point-max) t) > (setq mystring-list (append (list (match-string 1)) mystring-list))) > (insert "\n") > (setq mystring-list (reverse mystring-list)) > (dolist (elt mystring-list) > (insert elt " "))))) > > After evalling this code and typing `M-x mystring-list', buffer *test* > consists of these lines: > > +++++ test1 ~~~~~ > +++++ test2 ~~~~~ > +++++ test3 ~~~~~ > +++++ test4 ~~~~~ > +++++ test5 ~~~~~ > test1 test2 test3 test4 test5 > > The last line indicates that match-string correctly matches the > strings that build mystring-list. But when I step through the code > with edebug, match-string always returns nil and a wrong-type-argument > error is raised at the insert (since nil is not char-or-string-p). > (Edebug isn't the problem: evalling first the regexp search code in > *test* and then (match-string 1) also returns nil.) Because of this > I'm having a hard time debugging other code that uses match-string. > Can someone explain what's going on? re-search-forward uses global state (buffer, matched range, etc) as match-data, to communicate with match-string. When you're debugging, this global state is switched or modified. One could consider it a bug in the debugger. See: match-data save-match-data save-excursion save-buffer -- __Pascal Bourguignon__ http://www.informatimago.com/ Until real software engineering is developed, the next best practice is to develop with a dynamic system that has extreme late binding in all aspects. The first system to really do this in an important way is Lisp. -- Alan Kay