From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.help Subject: Re: Cycle Org Shift Select Date: Tue, 10 Nov 2020 12:10:53 +0100 Message-ID: <87h7pxeabm.fsf@web.de> References: <87pn4mgufa.fsf@web.de> <20201110080829.GA11023@tuxteam.de> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="38080"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:eKJ8eFR7phPb14AFmrVw6/4ysyk= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Nov 10 12:11:35 2020 Return-path: Envelope-to: geh-help-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 1kcRYl-0009oJ-5M for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 10 Nov 2020 12:11:35 +0100 Original-Received: from localhost ([::1]:48246 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kcRYk-0006W1-8Y for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 10 Nov 2020 06:11:34 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:44626) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kcRYN-0006Vh-Rz for help-gnu-emacs@gnu.org; Tue, 10 Nov 2020 06:11:11 -0500 Original-Received: from static.214.254.202.116.clients.your-server.de ([116.202.254.214]:45806 helo=ciao.gmane.io) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kcRYG-0004II-Pi for help-gnu-emacs@gnu.org; Tue, 10 Nov 2020 06:11:11 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1kcRYD-00099l-CR for help-gnu-emacs@gnu.org; Tue, 10 Nov 2020 12:11:01 +0100 X-Injected-Via-Gmane: http://gmane.org/ Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/10 06:11:01 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.25, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:125175 Archived-At: Christopher Dimech writes: > Many thanks Tomas, have gone though the Elisp Manual yesterday > and I am getting to understand this list Ouroboros thing. :) If you want a simple way to think about it starting from a syntax point of view: A very simple way to think about the dotted syntax is to start from regular lists. You can write (elt1 elt2 . rest) to describe a list of the elements elt1 elt2 (any positive number of starting elements will do) with the elements in the list `rest' appended. For example try to eval '(x y . ()) or '(x y . (z)) (You need the quote "'" because we don't want to evaluate the lists as an expression.) Of course the dot syntax is ambiguous, e.g. '(x y z) '(x . (y z)) '(x . (y . (z))) '(x . (y . (z . ()))) all describe equal three element lists containing the symbols x, y and z. Then you need to know that the "rest" can be actually anything. If the `rest' doesn't describe a regular list, you get a "dotted" list (it will be printed using the dot syntax). In the simplest case (x . y) you have a pair, a `cons' cell which is the building block lists are constructed from in Lisp. A cons with a list cdr is also a list. And when `rest' refers to the list itself (possible using the # reader syntax): '#1=(nil t always . #1#) you get a circular list. HTH, Michael.