From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Michael Heerdegen via "Emacs development discussions." Newsgroups: gmane.emacs.devel Subject: Re: Instead of pcase Date: Thu, 30 Nov 2023 21:30:00 +0100 Message-ID: <87il5jgf1z.fsf@web.de> References: <87fs169mjj.fsf@posteo.net> <093f11a1-57c2-5e56-d39b-26fef1c67cbb@gutov.dev> <25942.25061.217864.329049@retriever.mtv.corp.google.com> <87zfzdcz6z.fsf@posteo.net> <763f067b-4ca9-1eba-9f3c-424c38589e9c@gutov.dev> <83fs0navpj.fsf@gnu.org> Reply-To: Michael Heerdegen Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="33638"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: emacs-devel@gnu.org Cancel-Lock: sha1:IdOFXQnddDb8NXPpRT8bjFlBKqI= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Thu Nov 30 21:30:45 2023 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 1r8ngJ-0008UL-7M for ged-emacs-devel@m.gmane-mx.org; Thu, 30 Nov 2023 21:30:43 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r8nfY-0005T9-Nd; Thu, 30 Nov 2023 15:29:56 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r8nfX-0005Sy-Jg for emacs-devel@gnu.org; Thu, 30 Nov 2023 15:29:55 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r8nfW-0006Bf-1b for emacs-devel@gnu.org; Thu, 30 Nov 2023 15:29:55 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1r8nfS-0007RC-GA for emacs-devel@gnu.org; Thu, 30 Nov 2023 21:29:50 +0100 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: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:313407 Archived-At: Eli Zaretskii writes: > I think you are missing the point. The point is that pcase has so > many semi-magical syntax features that use punctuation characters in > creative ways that every extra punctuation character presents a > puzzle. Faced with > > (`(,hookfun . ,start ,end)) This is not a valid expression and will be rejected by the reader. Was it a typo or did you think this would be valid? > one immediately asks himself why the period, where in "normal" Lisp > expressions it would be completely redundant? As had been said: the syntax has been chosen intentionally to underline that it is important to view the matched thing as a cons instead of a list. If people get crazy about the dot, we can choose a different syntax without the dot. It is not necessary to use this syntax (unless the cdr is not a list). This point is not about `pcase' but about how the author has chosen to write the pattern. > The fact that it is there then leaves one wondering whether that > period has some "magical" meaning. As an alternative one can have a look at the docstring. And learn the read syntax of cons cells in Lisp. There is not more to wonder about as there is to wonder about the identity (X . (Y ...)) == (X Y ...) People should familiarize themselves a bit with Lisp when working with the Emacs Lisp source code. I know the above identity can be confusing _once_, in different situations, not only in `pcase', but it is something on has to know anyway, and this is really not that difficult or magical. Michael.