From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eric Abrahamsen Newsgroups: gmane.emacs.devel Subject: Re: Instead of pcase Date: Sun, 19 Nov 2023 11:31:39 -0800 Message-ID: <877cmdpmjo.fsf@ericabrahamsen.net> 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> <87zfza2aq2.fsf@web.de> <7nmsv9zq6u.fsf@ecube.ecubist.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="24935"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: emacs-devel@gnu.org Cancel-Lock: sha1:ojbQjhuP7ek8nqFc/GLjUcqrD+o= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Nov 19 20:52:44 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 1r4nqW-0006IY-Io for ged-emacs-devel@m.gmane-mx.org; Sun, 19 Nov 2023 20:52:44 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r4nqA-0004rg-MH; Sun, 19 Nov 2023 14:52:22 -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 1r4nWJ-0007uL-J6 for emacs-devel@gnu.org; Sun, 19 Nov 2023 14:31:52 -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 1r4nWH-0005ck-ND for emacs-devel@gnu.org; Sun, 19 Nov 2023 14:31:51 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1r4nWF-0000Dh-0g for emacs-devel@gnu.org; Sun, 19 Nov 2023 20:31:47 +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: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.25, 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-Mailman-Approved-At: Sun, 19 Nov 2023 14:52:20 -0500 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:313017 Archived-At: Dmitry Gutov writes: > On 19/11/2023 18:02, Barry Fishman wrote: >> On 2023-11-19 13:23:17 +01, Michael Heerdegen wrote: >>> So, the advantage would be more of a psychological kind: you have normal >>> Lisp function calls, but structurally you have the same thing, and you >>> have to remember exactly the same set of details. The complexity comes >>> from the task, not from the implementation. >> I submit that the opposite is true, the complexity is in its >> implementation, not the task. >> In languages like Haskell this is expressed in a very simple way, so >> the >> task is not in itself hard to understand. > > Haskell is notable for using the same (or similar) syntax for > destructuring as it uses for constructing expressions. > > pcase actually follows that practice with backquotes and commas. > > And in both matching and destructuring are done in the same expression > (the presence of the latter is determined by whether a pattern > contains variable bindindgs). +1, thanks for stating this so clearly in this and your earlier message. I agree that once you introduce guards/predicates, pcase gets ugly fast, but as you and Michael say, the core conceit is already as simple as it could be, and is deeply consonant with the already-understood meaning of the backquote.