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: The next exercise Date: Fri, 16 Dec 2022 00:17:54 +0100 Message-ID: <87mt7omf31.fsf@web.de> References: <87tu24tmv6.fsf@web.de> <574c1ceba8d5f62d3c07@heytings.org> <87edt8tklz.fsf@web.de> <574c1ceba8ee790f5f45@heytings.org> <87r0x8s3le.fsf@web.de> <87a63wuv1t.fsf@dataswamp.org> <87lendo15a.fsf@web.de> <87k02tute0.fsf@dataswamp.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="23979"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:VnFaQaJ3SMU0uOZQ4SBWdY8XHuk= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Fri Dec 16 00:18:38 2022 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 1p5xUs-00062g-Gi for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 16 Dec 2022 00:18:38 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p5xUN-0004Qy-7P; Thu, 15 Dec 2022 18:18:07 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p5xUL-0004Qj-HN for help-gnu-emacs@gnu.org; Thu, 15 Dec 2022 18:18:05 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p5xUJ-0003yJ-Tz for help-gnu-emacs@gnu.org; Thu, 15 Dec 2022 18:18:05 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1p5xUH-0005Fa-PR for help-gnu-emacs@gnu.org; Fri, 16 Dec 2022 00:18:01 +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-Spam_score_int: -15 X-Spam_score: -1.6 X-Spam_bar: - X-Spam_report: (-1.6 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.001, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.25, 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: 2.1.29 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-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.help:141787 Archived-At: Emanuel Berg writes: > > 2^2^43 - 1, right? What's it? It's too large to be the > > largest known prime number, or I calculated wrong. I don't > > know. Tell us. At least I know now it's not a prime, since all integers of the form 2^2^n - 1 are divisible by 5. > Hint 1: Start with (** 2 10) which is 1024. > Hint 2: Think computers, not math ... Is it some kind of Turing test? No, I'm not a computer, I swear. Hmm, what might I think about it as a computer? 2^2^43-1 is binary 1 1 .....................1 \_______________________/ 8 796 093 022 208 digits 1 so as a computer I would no doubt think, oh man, look at these 8 796 093 022 208 digits "1", I wounder what this is about - is it a prime? But I already answered that. Hmm. Still too mathematical maybe. Wait - it's the largest number a calculator using 8 796 093 022 208 binary digits can express. The horizontal checksum of this binary number is 2^43 - this is not some kind of "the answer is 42" joke? I'm not a good computer. I would obviously fail the inverse Turing test (as a human pretending to be a computer). Michael.