From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: Understanding the "let" construct and the setting of variables Date: Sat, 19 Dec 2020 00:15:54 -0500 Message-ID: References: <87zh2d1byp.fsf@fastmail.fm> <87tusk2754.fsf@fastmail.fm> <3b1a7936-913a-4736-9b12-0d3e04333c74@default> <87czz8dpsd.fsf@web.de> <20201218090128.GA27014@tuxteam.de> <87h7oj325p.fsf@web.de> <87o8iqyguv.fsf@zoho.eu> <87eejmo7xz.fsf@web.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="19256"; 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:G+qmfA33Zb3HTm/7Au401QCb1W0= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sat Dec 19 06:16:33 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 1kqUbZ-0004tr-O1 for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 19 Dec 2020 06:16:33 +0100 Original-Received: from localhost ([::1]:60608 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kqUbY-00005J-QR for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 19 Dec 2020 00:16:32 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:38186) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kqUb4-000059-FO for help-gnu-emacs@gnu.org; Sat, 19 Dec 2020 00:16:02 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]:49934) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kqUb2-00011i-W2 for help-gnu-emacs@gnu.org; Sat, 19 Dec 2020 00:16:02 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1kqUb1-0004H9-EC for help-gnu-emacs@gnu.org; Sat, 19 Dec 2020 06:15:59 +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: -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:126556 Archived-At: > t -> (lambda (&rest _) t) (fset t (lambda (&rest _) t)) seems to work fine here. > nil -> #'ignore This one does signal an error in `fset`. We could lift this error of course, but then we find other problems because nil is used as the marker that a function is "unbound", so subsequent calls to nil fail anyway. > 1 -> #'identity Here the problem is that 1 is not a symbol. You can do (fset '\1 #'identity) tho, after which (\1 42) returns 42. Stefan