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#24875: 26.0.50; In Dotted Pair Notation, the read function returns CDR if CAR is absent Date: Tue, 06 Jul 2021 12:43:58 -0400 Message-ID: References: <87fun7v02h.fsf@xuchunyang.me> <87zguzpiet.fsf@gnus.org> Reply-To: Stefan Monnier Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="37925"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) Cc: Chunyang Xu , 24875@debbugs.gnu.org To: Lars Ingebrigtsen Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Tue Jul 06 18:45:24 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 1m0oCK-0009fn-Mf for geb-bug-gnu-emacs@m.gmane-mx.org; Tue, 06 Jul 2021 18:45:24 +0200 Original-Received: from localhost ([::1]:52744 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m0oCJ-00062G-HO for geb-bug-gnu-emacs@m.gmane-mx.org; Tue, 06 Jul 2021 12:45:23 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:57746) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m0oBy-00061y-HR for bug-gnu-emacs@gnu.org; Tue, 06 Jul 2021 12:45:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:38362) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1m0oBx-0007UM-SD for bug-gnu-emacs@gnu.org; Tue, 06 Jul 2021 12:45:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1m0oBx-0003zL-RG for bug-gnu-emacs@gnu.org; Tue, 06 Jul 2021 12:45:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Stefan Monnier Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Tue, 06 Jul 2021 16:45:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 24875 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: moreinfo Original-Received: via spool by 24875-submit@debbugs.gnu.org id=B24875.162558985315254 (code B ref 24875); Tue, 06 Jul 2021 16:45:01 +0000 Original-Received: (at 24875) by debbugs.gnu.org; 6 Jul 2021 16:44:13 +0000 Original-Received: from localhost ([127.0.0.1]:49908 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1m0oBB-0003xy-0u for submit@debbugs.gnu.org; Tue, 06 Jul 2021 12:44:13 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:4067) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1m0oB9-0003xi-1O for 24875@debbugs.gnu.org; Tue, 06 Jul 2021 12:44:11 -0400 Original-Received: from pmg3.iro.umontreal.ca (localhost [127.0.0.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id 2376D441207; Tue, 6 Jul 2021 12:44:05 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id C8652440FDA; Tue, 6 Jul 2021 12:43:59 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1625589839; bh=2TxX8Lx8KJ7NY0/Ktz+xtyENl15bDN2ktENYFaGEc0o=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=cJqFQLZYKp6tbC2urH2NJpWCaZuldCUhbj0ga3Q+yFXmpArkapBVLuqAw+9fsyQnG 47fNGwMsJG2C5ubLk3fA6C1y0aNxVp/55vV1tVpOyD1U+cc7U7HpYqhnJ3iNSxFx72 KrhLQs5hzivbIo6KjBta1QtX2uvSbtba9gFU1H54DKA/SMNMJM9YLGjt52SdUbk9Nt to0VomG7fya8/iz4A1eLBsQKANJJMJnZlGeQaiaVmR1QkWa8FCmGg1Sqe7kuj+PSpX KmMuOiPaY4dNo2G+GqIHBMjtahLHfAxVy0PfTpzRtpui2QBGhTjCrmUkbtMoZKnve2 JxumbJw34Xqxw== Original-Received: from alfajor (unknown [45.72.205.238]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 94110120520; Tue, 6 Jul 2021 12:43:59 -0400 (EDT) In-Reply-To: <87zguzpiet.fsf@gnus.org> (Lars Ingebrigtsen's message of "Tue, 06 Jul 2021 17:32:26 +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:209548 Archived-At: Lars Ingebrigtsen [2021-07-06 17:32:26] wrote: > Chunyang Xu writes: > >> For example, I eval this in the *scratch* buffer: >> >> (read "( . 123)") >> =E2=87=92 123 >> >> (read "(1 . ( . (3 . nil)))") >> =E2=87=92 (1 3) >> >> I can't find explanation about this behavior in elisp manual. Is it >> expected? > > That is indeed very eccentric behaviour, so we should probably mention > it somewhere? (I guess we can't change it.) > > Anybody got an opinion here, or a way that we can describe it in the > manual except pointing at the examples and then going =C2=AF\_(=E3=83=84)= _/=C2=AF? It's the "natural" behavior if you start from (Ea . Ed) as the notation for cons cells and extend it to (E1 E2 E3 .. . Ed) such that (E1 {foo} . Ed) =3D (E1 . ({foo} . Ed)) because then you replace `{foo}` with the empty sequence and you get: (E1 . Ed) =3D (E1 . ( . Ed)) and hence Ed =3D ( . Ed) It's not used very often, so in theory we could potentially change it, but I haven't seen any good alternative interpretation for it, and I don't see the benefit of signaling an error. Stefan