From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Marcin Borkowski Newsgroups: gmane.emacs.help Subject: Re: Closures in Emacs and their usage scenarios. Date: Tue, 12 Oct 2021 07:29:07 +0200 Message-ID: <87ee8qu7z0.fsf@mbork.pl> References: <87r1ct3qzf.fsf@zoho.eu> <87mtngu48k.fsf@mbork.pl> <87zgrfywxb.fsf@zoho.eu> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="11003"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: mu4e 1.1.0; emacs 28.0.50 Cc: help-gnu-emacs@gnu.org To: Emanuel Berg Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Oct 12 07:29:54 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 1maAML-0002fW-Fp for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 12 Oct 2021 07:29:53 +0200 Original-Received: from localhost ([::1]:35154 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1maAMJ-0004ui-VJ for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 12 Oct 2021 01:29:51 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:53616) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1maALy-0004uR-2r for help-gnu-emacs@gnu.org; Tue, 12 Oct 2021 01:29:30 -0400 Original-Received: from mail.mojserwer.eu ([195.110.48.8]:46230) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1maALq-00080w-FH for help-gnu-emacs@gnu.org; Tue, 12 Oct 2021 01:29:28 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by mail.mojserwer.eu (Postfix) with ESMTP id BEB22E67FE; Tue, 12 Oct 2021 07:29:15 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.mojserwer.eu Original-Received: from mail.mojserwer.eu ([127.0.0.1]) by localhost (mail.mojserwer.eu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id W13THY5A2IeN; Tue, 12 Oct 2021 07:29:11 +0200 (CEST) Original-Received: from localhost (178235147138.dynamic-3-poz-k-0-1-0.vectranet.pl [178.235.147.138]) by mail.mojserwer.eu (Postfix) with ESMTPSA id 559F8E61D9; Tue, 12 Oct 2021 07:29:11 +0200 (CEST) In-reply-to: <87zgrfywxb.fsf@zoho.eu> Received-SPF: pass client-ip=195.110.48.8; envelope-from=mbork@mbork.pl; helo=mail.mojserwer.eu X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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:133738 Archived-At: On 2021-10-12, at 01:16, Emanuel Berg via Users list for the GNU Emacs text editor wrote: > Marcin Borkowski wrote: > >> Yet another use (which of course - technically - is again >> a variant of the same thing) is generating a closure whose >> behavior depends on the argument of the function that >> defines it. > > Not following? A function defines (and possibly returns) a closure. The behavior of the closure depends on the value of an argument to that function. Different arguments yield different functions. Just like the example below. >> (defun negate (fun) >> "Return a function returning the logical opposite of FUN." >> (lambda (&rest args) >> (not (apply fun args)))) > > Yes, I remember, no, I know you can do a lot with `lambda' > (anonymous function I believe :)), I mean just the > > (let ((...) ...) > (defun ... ) > ... > ) > > syntax Here are the 1 + a use cases I know of, where a -> 1. What's the difference? Doesn't `defun` contain an implicit `let' with the arguments? IOW, function arguments are much like local variables. Best, -- Marcin Borkowski http://mbork.pl