From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Code for cond* Date: Mon, 12 Feb 2024 21:27:48 -0500 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="28310"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: emacs-devel@gnu.org To: Richard Stallman Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Feb 13 03:28:25 2024 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 1rZiX2-00075V-VD for ged-emacs-devel@m.gmane-mx.org; Tue, 13 Feb 2024 03:28:25 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rZiWa-0006cY-AT; Mon, 12 Feb 2024 21:27:56 -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 1rZiWY-0006cO-Vf for emacs-devel@gnu.org; Mon, 12 Feb 2024 21:27:54 -0500 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rZiWX-0000GL-60; Mon, 12 Feb 2024 21:27:54 -0500 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 536CA10007D; Mon, 12 Feb 2024 21:27:51 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1707791270; bh=QSo0Wq1QutS/C+nTA1CnRGSkTJtvi0KHCLDphiRshP0=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=BFgMBA0VLTxZTPwBbsogstFDg9zaVk5KH6pjBEvnBraMivR2HA+CC2X9gk8IM8EUB QfYo9ym6np9g0dNEbA907Exertg0iBgaUN3owcJFuKeZX0DfDuILfQEOD6LE9EDH+n YZ2HFfPhVGeyPH/5RQRRy9PU4kghqyjstC21irKXiUM718du9iKFrZCkm7OJrl4rJ9 qte6R5BDwzHDnoGMs15HpN9ecozT+Pua8HK2TXreyHd286h9N9Xch2BBW8fIMg2n5G o/DrtSZMupDMRl5vvPQ/CDP31VPtZuIxG7AMXjBQqBIvB1473wXoDaVWMUpk1INszG cMw3DNeTpn6mA== Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 5757610004C; Mon, 12 Feb 2024 21:27:50 -0500 (EST) Original-Received: from pastel (unknown [104.247.238.113]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 17A251208E2; Mon, 12 Feb 2024 21:27:50 -0500 (EST) In-Reply-To: (Stefan Monnier's message of "Mon, 12 Feb 2024 19:48:55 -0500") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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:316160 Archived-At: > The main use-case I can think of for `cdr-ignore` is when matching > against things like Lisp code, where a pattern like > > `(lambda ,args . ,body) > > should also match (lambda) because (lambda) is a (broken) lambda > expression rather than being something *else* than a lambda expression. > > So I'm not sure the behavior you chose for `cdr-ignore` is the one > we want. BTW, here's what I used at one place to address this problem: (defmacro byte-optimize--pcase (exp &rest cases) ;; When we do ;; ;; (pcase EXP ;; (`(if ,exp ,then ,else) (DO-TEST)) ;; (`(plus ,e2 ,e2) (DO-ADD)) ;; (`(times ,e2 ,e2) (DO-MULT)) ;; ...) ;; ;; we usually don't want to fall back to the default case if ;; the value of EXP is of a form like `(if E1 E2)' or `(plus E1)' ;; or `(times E1 E2 E3)', instead we either want to signal an error ;; that EXP has an unexpected shape, or we want to carry on as if ;; it had the right shape (ignore the extra data and pretend the missing ;; data is nil) because it should simply never happen. ;; ;; The macro below implements the second option by rewriting patterns ;; like `(if ,exp ,then ,else)' ;; to `(if . (or `(,exp ,then ,else) pcase--dontcare))'. ;; ;; The resulting macroexpansion is also significantly cleaner/smaller/faster. (declare (indent 1) (debug pcase)) `(pcase ,exp . ,(mapcar (lambda (case) `(,(pcase (car case) ((and `(,'\` (,_ . (,'\, ,_))) pat) pat) (`(,'\` (,head . ,tail)) (list '\` (cons head (list '\, `(or ,(list '\` tail) pcase--dontcare))))) (pat pat)) . ,(cdr case))) cases))) - Stefan