From mboxrd@z Thu Jan  1 00:00:00 1970
Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail
From: Adam Porter <adam@alphapapa.net>
Newsgroups: gmane.emacs.devel
Subject: Re: thunk.el: Document that thunk-force == funcall?
Date: Thu, 17 Dec 2020 20:58:09 -0600
Message-ID: <873603n7lq.fsf@alphapapa.net>
References: <871rgs3tdx.fsf@web.de> <jwv4klnejwi.fsf-monnier+emacs@gnu.org>
 <87v9dtttbr.fsf@web.de> <87im9qhfz5.fsf@web.de>
 <878s9xyrn2.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="11271"; mail-complaints-to="usenet@ciao.gmane.io"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux)
To: emacs-devel@gnu.org
Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Dec 18 03:59:43 2020
Return-path: <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>
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 <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>)
	id 1kq5zb-0002pw-EM
	for ged-emacs-devel@m.gmane-mx.org; Fri, 18 Dec 2020 03:59:43 +0100
Original-Received: from localhost ([::1]:35704 helo=lists1p.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.90_1)
	(envelope-from <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>)
	id 1kq5za-00046f-GG
	for ged-emacs-devel@m.gmane-mx.org; Thu, 17 Dec 2020 21:59:42 -0500
Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:48630)
 by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <ged-emacs-devel@m.gmane-mx.org>)
 id 1kq5yF-0002zk-KV
 for emacs-devel@gnu.org; Thu, 17 Dec 2020 21:58:19 -0500
Original-Received: from ciao.gmane.io ([116.202.254.214]:53778)
 by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <ged-emacs-devel@m.gmane-mx.org>)
 id 1kq5yD-0008GW-3d
 for emacs-devel@gnu.org; Thu, 17 Dec 2020 21:58:19 -0500
Original-Received: from list by ciao.gmane.io with local (Exim 4.92)
 (envelope-from <ged-emacs-devel@m.gmane-mx.org>) id 1kq5yB-00015r-9n
 for emacs-devel@gnu.org; Fri, 18 Dec 2020 03:58:15 +0100
X-Injected-Via-Gmane: http://gmane.org/
Received-SPF: pass client-ip=116.202.254.214;
 envelope-from=ged-emacs-devel@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,
 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: emacs-devel@gnu.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: "Emacs development discussions." <emacs-devel.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/emacs-devel>,
 <mailto:emacs-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/emacs-devel>
List-Post: <mailto:emacs-devel@gnu.org>
List-Help: <mailto:emacs-devel-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/emacs-devel>,
 <mailto:emacs-devel-request@gnu.org?subject=subscribe>
Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org
Original-Sender: "Emacs-devel"
 <emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org>
Xref: news.gmane.io gmane.emacs.devel:261147
Archived-At: <http://permalink.gmane.org/gmane.emacs.devel/261147>

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Michael Heerdegen <michael_heerdegen@web.de> writes:
>
>> Actually I have one real-life example:
>
> An example involving side effects: being able to create a function
> that one can add to a hook that performs some kind of (expensive) setup
> but only when called for the first time.

FYI, someone recently showed me that the letrec macro can be used to do
this.  There's an example of it in the Elisp manual, section 12.3 Local
Variables (added about a year ago, so I think most Emacs users don't
know of it yet).