From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Andreas Schwab Newsgroups: gmane.emacs.devel Subject: Re: "The starting list count" ????? Date: Mon, 03 Jan 2022 19:33:20 +0100 Message-ID: <874k6k1xfz.fsf@igel.home> References: <4b0fc44c-8ef2-e6c8-0146-1497fe43acf7@dasyatidae.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="27802"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.90 (gnu/linux) Cc: acm@muc.de, emacs-devel@gnu.org To: Robin Tarsiger Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Jan 03 19:34:24 2022 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 1n4SA3-00072g-HN for ged-emacs-devel@m.gmane-mx.org; Mon, 03 Jan 2022 19:34:23 +0100 Original-Received: from localhost ([::1]:52436 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1n4SA2-0007BM-FF for ged-emacs-devel@m.gmane-mx.org; Mon, 03 Jan 2022 13:34:22 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:58762) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n4S9B-0006D8-9G for emacs-devel@gnu.org; Mon, 03 Jan 2022 13:33:29 -0500 Original-Received: from mail-out.m-online.net ([212.18.0.10]:59962) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n4S96-0006oF-F8 for emacs-devel@gnu.org; Mon, 03 Jan 2022 13:33:26 -0500 Original-Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4JSPWk0RYcz1sCwh; Mon, 3 Jan 2022 19:33:22 +0100 (CET) Original-Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4JSPWj708Wz1qqkM; Mon, 3 Jan 2022 19:33:21 +0100 (CET) X-Virus-Scanned: amavisd-new at mnet-online.de Original-Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id HkYGZ3K1YpBt; Mon, 3 Jan 2022 19:33:21 +0100 (CET) X-Auth-Info: bO7ScndsJ0r+WqADTfbbgSC7jvBnZYp9rxyw8KuH3qhfyrJ+Tjv4dU+HoxRtPZss Original-Received: from igel.home (ppp-46-244-172-77.dynamic.mnet-online.de [46.244.172.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Mon, 3 Jan 2022 19:33:21 +0100 (CET) Original-Received: by igel.home (Postfix, from userid 1000) id D6CD22C3A42; Mon, 3 Jan 2022 19:33:20 +0100 (CET) X-Yow: I have no actual hairline... In-Reply-To: <4b0fc44c-8ef2-e6c8-0146-1497fe43acf7@dasyatidae.com> (Robin Tarsiger's message of "Mon, 3 Jan 2022 12:00:29 -0600") Received-SPF: pass client-ip=212.18.0.10; envelope-from=whitebox@nefkom.net; helo=mail-out.m-online.net X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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" Xref: news.gmane.io gmane.emacs.devel:284085 Archived-At: On Jan 03 2022, Robin Tarsiger wrote: > Alan Mackenzie wrote: >> `#N' >> When printing circular structures, this construct is used to >> represent where the structure loops back onto itself, and `N' is >> the starting list count: >> (let ((a (list 1))) >> (setcdr a a)) >> => (1 . #0) >> .. What does this mean, please? What does "is the starting list count" >> mean? There is only one "list", so what is the "list count"? > > I agree that this is a bit too abbreviated, but basically it's the number > you'd pass to nthcdr along with the immediately enclosing list to get what's > spliced in as that last cdr. It gets more complicated if the circle is embedded inside another object. ELISP> (list (let ((a (list 1))) (setcdr a a))) ((1 . #1)) -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."