From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Andrea Corallo via "Emacs development discussions." Newsgroups: gmane.emacs.devel Subject: Re: Always-true predicate? Date: Wed, 17 Feb 2021 12:31:57 +0000 Message-ID: References: <875z2qoqc6.fsf@gnus.org> Reply-To: Andrea Corallo Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="38240"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) Cc: emacs-devel@gnu.org To: Lars Ingebrigtsen Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Wed Feb 17 13:32:55 2021 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 1lCM0l-0009pt-AX for ged-emacs-devel@m.gmane-mx.org; Wed, 17 Feb 2021 13:32:55 +0100 Original-Received: from localhost ([::1]:59584 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lCM0k-0004Hs-B8 for ged-emacs-devel@m.gmane-mx.org; Wed, 17 Feb 2021 07:32:54 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:57882) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lCLzu-0003m0-VY for emacs-devel@gnu.org; Wed, 17 Feb 2021 07:32:03 -0500 Original-Received: from mx.sdf.org ([205.166.94.24]:53327) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lCLzs-0003v0-S2 for emacs-devel@gnu.org; Wed, 17 Feb 2021 07:32:02 -0500 Original-Received: from mab (ma.sdf.org [205.166.94.33]) by mx.sdf.org (8.15.2/8.14.5) with ESMTPS id 11HCVvvA001527 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits) verified NO); Wed, 17 Feb 2021 12:31:57 GMT In-Reply-To: <875z2qoqc6.fsf@gnus.org> (Lars Ingebrigtsen's message of "Wed, 17 Feb 2021 13:01:45 +0100") Received-SPF: pass client-ip=205.166.94.24; envelope-from=akrl@sdf.org; helo=mx.sdf.org X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham 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." 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:264995 Archived-At: Lars Ingebrigtsen writes: > Currently, Emacs has: > > ---- > Sometimes, when you call a functional, it is useful to supply a no-op > function as the argument. Here are two different kinds of no-op > function: > > -- Function: identity argument > This function returns ARGUMENT and has no side effects. > > -- Function: ignore &rest arguments > This function ignores any ARGUMENTS and returns =E2=80=98nil=E2=80= =99. > ---- > > `identity' is kinda-sorta used as the opposite of `ignore' many places > where you're feeding predicates to functions, but takes only one > parameter and, of course, returns nil if you give it nil. > > Would it make sense to add a function that's exactly the opposite of > `ignore' (for symmetry and convenience)? If so, what would it be > called? > > I've googled to see what other languages do. Rust and NPM has "always", > and many more Java-inspired frameworks have "truePredicate", but this > isn't trivial to google for... Maybe something like CONSTANTLY would be more generic? Andrea