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: Negative nth index Date: Tue, 24 Dec 2024 10:18:20 -0500 Message-ID: References: <865xnc6u9n.fsf@gnu.org> <87jzbs9jlk.fsf@gnu.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="11494"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: Tassilo Horn , Eli Zaretskii , Anand Tamariya , emacs-devel@gnu.org To: Stefan Kangas Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Dec 24 16:20:15 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 1tQ6hi-0002pS-W2 for ged-emacs-devel@m.gmane-mx.org; Tue, 24 Dec 2024 16:20:15 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tQ6gL-0002Sb-QY; Tue, 24 Dec 2024 10:18:50 -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 1tQ6g0-000261-Qv for emacs-devel@gnu.org; Tue, 24 Dec 2024 10:18:32 -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 1tQ6fz-0004Eq-69; Tue, 24 Dec 2024 10:18:28 -0500 Original-Received: from pmg2.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 35AEA807D7; Tue, 24 Dec 2024 10:18:22 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1735053501; bh=QlAenWpczqNwODLJQkj6vEbUkL3c1gBgUseaz2oj01Y=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=JEZhGWH53PYhkK9lzBp+x3NP/jJKjr8IagxV1t//sEATh77Rc3Uk4oiedXxBwhUR+ WA79WrYh/T5jM32cNn4QQj1ln19byZEG8l9AP9Y1q7lGJKwWBv5swt62A2CBoipeSb lTia7mIkLhCgKKr08rRKW+95plf5VdwuKaet2aPWFuw2a8zYJLt6LRYfqwd1ruoVpi QutP6kgOatg/xqwy1b85WK1Fdh80OpDaOxSm+z5d9WuzrTx0wnXfGdHcrsNZJBVsb+ Yhvq7QtFlbzcAMBk8Z4yy39guf9Is3/kV+UHLGsKdbAn9U76Id1jDgIeW1DAU+TBPm TurG2pYtZDw8Q== Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 748EC803A3; Tue, 24 Dec 2024 10:18:21 -0500 (EST) Original-Received: from pastel (104-195-225-43.cpe.teksavvy.com [104.195.225.43]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 384C9120409; Tue, 24 Dec 2024 10:18:21 -0500 (EST) In-Reply-To: (Stefan Monnier's message of "Tue, 24 Dec 2024 00:11:26 -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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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:327022 Archived-At: > I don't see a strong argument in favor of making it index from the end > rather than signal an error. What would the implementation look like? > Would it be significantly more efficient than doing it "by hand" e.g.: > > (let ((l (length X))) > (nth (if (< i 0) (- l i) i) X)) AFAICT so far people were only able to fix my code but not answer my question, which suggests the answer is no, which would be a good argument in favor of staying with the current behavior: the change wouldn't save us from going down the list twice. Stefan