From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#56641: Deprecate `lsh` Date: Wed, 20 Jul 2022 13:57:27 +0200 Message-ID: <752C35EB-B86F-4D5B-863D-D9AFDFE20A66@acm.org> References: <83zgh5mcqk.fsf@gnu.org> <52FF0BFF-F19C-4ABA-82BE-8FE3277B726D@acm.org> <83lespm50p.fsf@gnu.org> <87cze0bmn6.fsf@yahoo.com> <83bktkmrwx.fsf@gnu.org> <877d48bhch.fsf@yahoo.com> Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.13\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="33639"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Eli Zaretskii , stefankangas@gmail.com, 56641@debbugs.gnu.org To: Po Lu Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Wed Jul 20 13:58:19 2022 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 1oE8LL-0008Z7-Ky for geb-bug-gnu-emacs@m.gmane-mx.org; Wed, 20 Jul 2022 13:58:19 +0200 Original-Received: from localhost ([::1]:49422 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oE8LK-00031k-JH for geb-bug-gnu-emacs@m.gmane-mx.org; Wed, 20 Jul 2022 07:58:18 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:39316) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oE8L4-0002xG-UG for bug-gnu-emacs@gnu.org; Wed, 20 Jul 2022 07:58:05 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:58285) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1oE8L4-0007NF-MC for bug-gnu-emacs@gnu.org; Wed, 20 Jul 2022 07:58:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1oE8L4-0006qn-FB for bug-gnu-emacs@gnu.org; Wed, 20 Jul 2022 07:58:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Wed, 20 Jul 2022 11:58:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 56641 X-GNU-PR-Package: emacs Original-Received: via spool by 56641-submit@debbugs.gnu.org id=B56641.165831825926300 (code B ref 56641); Wed, 20 Jul 2022 11:58:02 +0000 Original-Received: (at 56641) by debbugs.gnu.org; 20 Jul 2022 11:57:39 +0000 Original-Received: from localhost ([127.0.0.1]:56044 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1oE8Kg-0006q7-Ru for submit@debbugs.gnu.org; Wed, 20 Jul 2022 07:57:39 -0400 Original-Received: from mail18c50.megamailservers.eu ([91.136.10.28]:50902) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1oE8Kc-0006pw-24 for 56641@debbugs.gnu.org; Wed, 20 Jul 2022 07:57:37 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1658318252; bh=TUC6wSBWjokmysJnfXxRpuXi0WFBwj2wgiy14foY6TU=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=cwnrwSDARIXegOozygFViyJbx2A0PgZp5dNaDPy40wcOJ81qdjdWAzpKdx8K+IKcY Md/RX/94iEFIOaaEM9bDh/S1mgpQwYz1k2/cQmE4KGqecDEQwtfxnLUEqpOFnct9iB SjQ0RDuMRBzWKfaKy+Bia7pza/shAOaLD0Bdheyw= Feedback-ID: mattiase@acm.or Original-Received: from smtpclient.apple (c188-150.188-179.bredband.tele2.se [188.150.188.179] (may be forged)) (authenticated bits=0) by mail18c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 26KBvSTA070972; Wed, 20 Jul 2022 11:57:29 +0000 In-Reply-To: <877d48bhch.fsf@yahoo.com> X-Mailer: Apple Mail (2.3654.120.0.1.13) X-CTCH-RefID: str=0001.0A782F1B.62D7EDAC.0025, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-Origin-Country: SE 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:237494 Archived-At: 20 juli 2022 kl. 05.20 skrev Po Lu : > It might be rare, but there's nothing wrong with using lsh for its > intended purpose, which is handling negative numbers correctly in > several different situations. The purpose of `lsh` is not breaking old code. (It used to have a = different purpose but it vanished when bignums were introduced.) There is no reasonable use for it in new code. Even in the unlikely = event of code that just happens to need that sort of quirky behaviour, = it is much better implemented explicitly where it's used, in terms of = `ash`. > Byte-compiler warnings are supposed to point out problems. Using lsh = is > not a problem You are right that most uses of `lsh` are perfectly innocuous but that's = because they are used in a way where `ash` would give the same result. = This is often true even when the return values of `lsh` and `ash` = differ, as in (logand (lsh x -16) #xff) which would give the same result even for negative x if `lsh` were = replaced with `ash`. However there is a potential problem since the behaviour of `lsh` is = strongly platform-dependent, and it's impossible to write correct code = without taking that into account (consider replacing -16 with -24 = above). Users may not be aware of how it works and mistakenly think it = is the 'unsigned' or 'logical' shift that they know from other = languages.