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 Users list for the GNU Emacs text editor Newsgroups: gmane.emacs.help Subject: [OFFTOPIC] Re: Appending lists Date: Wed, 16 Jun 2021 22:41:18 -0400 Message-ID: References: <4tl1yvylvg1fxx5eefjs9mnk.1623688568572@email.android.com> <87o8c8l32h.fsf@posteo.net> <87zgvs2bup.fsf@zoho.eu> <87y2bby1kr.fsf@zoho.eu> <20210615091834.GB24886@tuxteam.de> <87im2ewr3k.fsf@zoho.eu> <20210616072819.GB17919@tuxteam.de> <20210616151101.GB5669@tuxteam.de> <875yydtnqz.fsf@zoho.eu> Reply-To: Stefan Monnier Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="36952"; 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:qRiYVe99zg7pneNF2MVhm7fQfDs= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Thu Jun 17 04:41:54 2021 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 1lthyc-0009W2-34 for geh-help-gnu-emacs@m.gmane-mx.org; Thu, 17 Jun 2021 04:41:54 +0200 Original-Received: from localhost ([::1]:54580 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lthyb-0001Jf-4b for geh-help-gnu-emacs@m.gmane-mx.org; Wed, 16 Jun 2021 22:41:53 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:35702) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lthyC-0001Gu-Hh for help-gnu-emacs@gnu.org; Wed, 16 Jun 2021 22:41:28 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:58268) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lthyA-0007Yg-VB for help-gnu-emacs@gnu.org; Wed, 16 Jun 2021 22:41:28 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1lthy8-00091M-5C for help-gnu-emacs@gnu.org; Thu, 17 Jun 2021 04:41:24 +0200 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-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, 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:130947 Archived-At: >>>> Just to show that you should never say never: >>> Hey, that's cheating :-) >> Impredicativity is borderline, indeed. > Impredicativity, what's that, recursion? (with-lecture-mode Kind of, except the cycle is not "definition refers to itself" (the "traditional" form of recursion) but rather "definition can be applied to itself" as in the first sentence quoted above ;-) These forms of circularity have been a great source of hilarity for logicians and philosophers over the years, but more relevantly for programmers they've been the source of the invention of the notion of "type", introduced by Bertrand Russel about a century ago to try and rule out those forms of circularity by stratifying logical statements. ) Stefan