From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Tomas Hlavaty Newsgroups: gmane.emacs.devel Subject: Re: using finalizers Date: Sun, 02 Jan 2022 00:26:42 +0100 Message-ID: <87wnjjjavh.fsf@logand.com> References: <878rw1pvcw.fsf@logand.com> <875yr5p9t3.fsf@logand.com> <877dbjkxui.fsf@logand.com> <8735m7kqvq.fsf@logand.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="15369"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Jan 02 00:27:24 2022 Return-path: Envelope-to: ged-emacs-devel@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 1n3nmW-0003oX-QM for ged-emacs-devel@m.gmane-mx.org; Sun, 02 Jan 2022 00:27:24 +0100 Original-Received: from localhost ([::1]:58070 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1n3nmU-0004ag-Tl for ged-emacs-devel@m.gmane-mx.org; Sat, 01 Jan 2022 18:27:22 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:40292) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n3nlv-0003qP-Rg for emacs-devel@gnu.org; Sat, 01 Jan 2022 18:26:47 -0500 Original-Received: from logand.com ([37.48.87.44]:40556) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n3nlu-00078B-3c for emacs-devel@gnu.org; Sat, 01 Jan 2022 18:26:47 -0500 Original-Received: by logand.com (Postfix, from userid 1001) id 4D14219EC87; Sun, 2 Jan 2022 00:26:44 +0100 (CET) X-Mailer: emacs 27.2 (via feedmail 11-beta-1 I) In-Reply-To: <8735m7kqvq.fsf@logand.com> Received-SPF: pass client-ip=37.48.87.44; envelope-from=tom@logand.com; helo=logand.com X-Spam_score_int: 0 X-Spam_score: -0.0 X-Spam_bar: / X-Spam_report: (-0.0 / 5.0 requ) SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:283834 Archived-At: On Sat 01 Jan 2022 at 23:55, Tomas Hlavaty wrote: > On Sat 01 Jan 2022 at 15:47, Stefan Monnier wrote: >> That's right: if you want an object to have a finalizer, you need to >> save that finalizer somewhere inside the object. >> IOW the object literally "has a finalizer" somewhere inside. >> >> There's no doubt that it's different. >> Do you have concrete cases where this difference introduces a difficulty? > > In my original example: > > (defun finito () > (let ((x '(a b c))) > (letrec ((more (make-finalizer close)) > (close (lambda () > (print "close-resource") > (setq more nil)))) > (lambda () > (when more > (pop x)))))) > > I use a closure as my object that should have the finalizer "attached" > to. In order to keep the reference to the finalizer, I have to use it > inside the closure for something (here I stuffed it into the variable > called more). That is inconvenient. Second issue is that an advanced > compiler could eliminate even my attempt at using the finalizer for > something if it determines that the finalizer is not actually used for > something. For comparison in Common Lisp, my object would not need to reference the finalizer. Something like this: (defun finito () (let* ((x '(a b c)) (close (lambda () (print "close-resource"))) (object (lambda () (pop x)))) (finalize object close) object))