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: Mutation - do you understand it really? Date: Sat, 10 Dec 2022 19:29:00 +0100 Message-ID: <87pmcrkt8z.fsf@web.de> References: <87lenh7vrn.fsf@web.de> <87tu25d77o.fsf@gnu.org> <87h6y5pt8k.fsf@web.de> <87bkodpqnk.fsf@web.de> <87k030tlfh.fsf@web.de> <87ilikxgkd.fsf@web.de> <87y1rf1txv.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="32331"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:edpEK6PTuANKUIacizkeg3SgYOw= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sat Dec 10 19:29:37 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 1p44bP-0008Cx-TQ for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 10 Dec 2022 19:29:35 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p44b2-0003Oz-05; Sat, 10 Dec 2022 13:29:12 -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 1p44b0-0003Oo-G8 for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 13:29:10 -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 1p44az-0003tr-54 for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 13:29:10 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1p44ax-0007eB-Lr for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 19:29:07 +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: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.249, 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: 2.1.29 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:141593 Archived-At: Stefan Monnier via Users list for the GNU Emacs text editor writes: > Immutable variables are just a lot better behaved (and easier to work > with for the compiler, which is why GCC/LLVM/... use an SSA conversion > to replace those nasty mutable variables with immutable ones). The original question used `setq'. I presented it to a friend that knows lambda calculus and Haskell very well, but Lisp not at all. When he asked "what does this setq do" and I gave an answer he was shocked that these bindings are mutual in Lisp and his reaction was like "WTF?...Ok, then...". But mutable variable bindings are a legitimate aspect of semantics of closures in Lisp - I hope I didn't scare anybody. When there is an intention then it is to hint at pitfalls so that people know them before they cause trouble. Michael.