From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Helmut Eller Newsgroups: gmane.emacs.devel Subject: Re: Make peg.el a built-in library? Date: Sat, 09 Oct 2021 10:12:03 +0200 Message-ID: References: <875yvtbbn3.fsf@ericabrahamsen.net> <87a6jjc7c8.fsf@web.de> <87zgri22e2.fsf@web.de> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="29979"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) To: emacs-devel@gnu.org Cancel-Lock: sha1:SXgI8gexLMQkcwXND6dl4WWhuas= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Oct 09 10:13:05 2021 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mZ7Td-0007Zm-KS for ged-emacs-devel@m.gmane-mx.org; Sat, 09 Oct 2021 10:13:05 +0200 Original-Received: from localhost ([::1]:59842 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mZ7Tb-00012C-Q1 for ged-emacs-devel@m.gmane-mx.org; Sat, 09 Oct 2021 04:13:03 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:46012) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mZ7Sn-0000Fs-0V for emacs-devel@gnu.org; Sat, 09 Oct 2021 04:12:13 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:42038) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mZ7Sk-0004SR-Us for emacs-devel@gnu.org; Sat, 09 Oct 2021 04:12:12 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1mZ7Sj-0006ck-5d for emacs-devel@gnu.org; Sat, 09 Oct 2021 10:12:09 +0200 X-Injected-Via-Gmane: http://gmane.org/ Received-SPF: pass client-ip=116.202.254.214; envelope-from=ged-emacs-devel@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: 5 X-Spam_score: 0.5 X-Spam_bar: / X-Spam_report: (0.5 / 5.0 requ) BAYES_00=-1.9, DKIM_ADSP_CUSTOM_MED=0.001, FORGED_GMAIL_RCVD=1, FREEMAIL_FORGED_FROMDOMAIN=0.25, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.25, NML_ADSP_CUSTOM_MED=0.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:276596 Archived-At: On Sat, Oct 09 2021, Michael Heerdegen wrote: >> "how do you jump over arbitrary text preceding a match?" (the answer >> seems to be: "use `or' and recursion", at least this is what I found >> out by myself after a while). > > No - using recursive rules of the kind > > (rule [maches what I want]) > (search (or rule (and (any) search))) > > to advance over preceding text is not a good method in Emacs, this hits > Emacs' maximum recursion level after a bunch of lines if we advance one > character each time (which can't be avoided when searching text). Is > there a better solution for this kind of problem? Self-recursion can sometimes be rewritten using *. In peg.el, * is "inlined" and so doesn't run out of stack: (rule [maches what I want]) (search (and (* (not rule) (any)) rule)) It's kinda like rewriting a self tail call to a while loop. For the general case, peg.el would need some form of proper tail calls. Helmut