From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" Newsgroups: gmane.emacs.bugs Subject: bug#49809: [PATCH] Add macro 'pcase-setq' Date: Thu, 12 Aug 2021 12:13:58 -0400 Message-ID: References: <07ad5892-3343-4c35-00e3-9753bca5f67b@protonmail.com> <87im0fwjep.fsf@web.de> <87eeb22drs.fsf@web.de> Reply-To: Stefan Monnier Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="10164"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) Cc: Okam , 49809@debbugs.gnu.org To: Michael Heerdegen Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Thu Aug 12 18:19:44 2021 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1mEDQl-0002Qp-5d for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 12 Aug 2021 18:19:43 +0200 Original-Received: from localhost ([::1]:60068 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mEDQj-0001ZN-SW for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 12 Aug 2021 12:19:41 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:41296) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mEDME-00034Y-Q8 for bug-gnu-emacs@gnu.org; Thu, 12 Aug 2021 12:15:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:56500) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mEDME-0002tC-I0 for bug-gnu-emacs@gnu.org; Thu, 12 Aug 2021 12:15:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1mEDME-0002WZ-9Z for bug-gnu-emacs@gnu.org; Thu, 12 Aug 2021 12:15:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Stefan Monnier Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Thu, 12 Aug 2021 16:15:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 49809 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: patch Original-Received: via spool by 49809-submit@debbugs.gnu.org id=B49809.16287848519615 (code B ref 49809); Thu, 12 Aug 2021 16:15:02 +0000 Original-Received: (at 49809) by debbugs.gnu.org; 12 Aug 2021 16:14:11 +0000 Original-Received: from localhost ([127.0.0.1]:39813 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1mEDLP-0002V1-BI for submit@debbugs.gnu.org; Thu, 12 Aug 2021 12:14:11 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:20845) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1mEDLL-0002U9-0E for 49809@debbugs.gnu.org; Thu, 12 Aug 2021 12:14:10 -0400 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 2406A1001FC; Thu, 12 Aug 2021 12:14:01 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id D62D2100091; Thu, 12 Aug 2021 12:13:59 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1628784839; bh=MsPOJl2u0KXuIT+HKAoGJYXJc7M7st7eaVfydtjkzcI=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=lUn6n3hhkcVNFIlc3id2AU7WPbQlKew2kBFLudu0WRa7Mk9U3/RXNIKDzu4sFk+lz kfafma5dWl4WkiAzMY7zqCHly478zHUw0vgFSEeKzKsvYpy/9dgYzlnlVuDMji9res 2hMlg7ofTykNxQ0/iStLqS/jjAe46t7rU2A5AS1n4brKGmTiSBeFn3hDfeuEZUnu1K 3r8Z/syjdoiGeY1KTGdAeTLJU/oKbgxNKFRqzEBjiuJvr80jo0whkAJ4hu+U8qUt8K v92HG/hutkskP/+tWX8zeveNMC3/0G2pUgCMgKfPtYR1zeTkVWwbxvwZv4VZo85Wpc jSlYdAY4eqaoQ== Original-Received: from alfajor (104-222-120-40.cpe.teksavvy.com [104.222.120.40]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 9F1D21203D8; Thu, 12 Aug 2021 12:13:59 -0400 (EDT) In-Reply-To: <87eeb22drs.fsf@web.de> (Michael Heerdegen's message of "Tue, 10 Aug 2021 05:13:11 +0200") X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:211703 Archived-At: > Undefined behavior has no use per se, unless it has a larger impact on > efficiency. There is indeed a significant difference in efficiency. E.g. the code for (pcase-let ((`(,x ,y) (EXP))) (VAL x y)) looks like: byte code: args: nil 0 constant EXP 1 call 0 2 dup 3 car-safe 4 stack-ref 1 5 cdr-safe 6 dup 7 car-safe 8 stack-ref 1 9 cdr-safe 10 stack-ref 3 11 stack-ref 2 12 constant VAL 13 stack-ref 2 14 stack-ref 2 15 call 2 16 return Instead of: byte code: args: nil 0 constant EXP 1 call 0 2 dup 3 consp 4 goto-if-nil-else-pop 3 7 dup 8 car-safe 9 stack-ref 1 10 cdr-safe 11 dup 12 consp 13 goto-if-nil-else-pop 2 16 dup 17 car-safe 18 stack-ref 1 19 cdr-safe 20 dup 21 not 22 goto-if-nil-else-pop 1 25 stack-ref 3 26 stack-ref 2 27 constant VAL 28 stack-ref 2 29 stack-ref 2 30 call 2 31 discardN-preserve-tos 2 33:1 discardN-preserve-tos 2 35:2 discardN-preserve-tos 2 37:3 return For a semantic where the let is skipped when the pattern fails to match and byte code: args: nil 0 constant EXP 1 call 0 2 dup 3 consp 4 goto-if-nil 3 7 dup 8 car-safe 9 stack-ref 1 10 cdr-safe 11 dup 12 consp 13 goto-if-nil 2 16 dup 17 car-safe 18 stack-ref 1 19 cdr-safe 20 dup 21 goto-if-nil 1 24 stack-ref 4 25 constant error 26 constant "No clause matching `%S'" 27 stack-ref 2 28 call 2 29 return 30:1 stack-ref 3 31 stack-ref 2 32 constant VAL 33 stack-ref 2 34 stack-ref 2 35 call 2 36 return 37:2 stack-ref 2 38 constant error 39 constant "No clause matching `%S'" 40 stack-ref 2 41 call 2 42 return 43:3 dup 44 constant error 45 constant "No clause matching `%S'" 46 stack-ref 2 47 call 2 48 return For the semantics where we signal an error when the pattern fails to match. > And why again do you think it is not a good idea? Because if you want different behaviors when the pattern matches and when it doesn't, you should use `pcase`. Stefan