From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Why shouldn't we have a #if .... #else .... #endif construct in Emacs Lisp? Date: Mon, 28 Aug 2023 21:46:46 +0000 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="12649"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Ulrich Mueller Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Aug 28 23:47:41 2023 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 1qak5F-00035v-Bq for ged-emacs-devel@m.gmane-mx.org; Mon, 28 Aug 2023 23:47:41 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qak4X-0004O8-7i; Mon, 28 Aug 2023 17:46:57 -0400 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 1qak4V-0004MV-7O for emacs-devel@gnu.org; Mon, 28 Aug 2023 17:46:55 -0400 Original-Received: from mail.muc.de ([193.149.48.3]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qak4S-0007yY-9o for emacs-devel@gnu.org; Mon, 28 Aug 2023 17:46:54 -0400 Original-Received: (qmail 4307 invoked by uid 3782); 28 Aug 2023 23:46:48 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=muc.de; i=@muc.de; q=dns/txt; s=default; t=1693259208; h=date : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to : from : from; bh=StbSlh1alEppumv2GOQtFChbJxWfBhC+mP4UA1LJR5U=; b=MU1cJ6Jdx1yr4DJlHsSUa5LfXNFay182oZIWDbJ4RB2N3WodHr4YFXtrlkvHwzLJtXlhL R/uOBPtsHfNEln3eP7r+39Yk1KxS6Uf0BEoFS4h+3SmPT11aN6hfO0tDf72BUUVnvxb68Zp 441gavZRV0D4GPZtxqTPZDvkFblflEiC0ISIYBm8I7vA9rszqhUW1n1EyNdssbrDC2DBAYc xcDeUHbliLRc9x/Rx6C/VwJM6IpyHSV3IOtJaCqsT/LAuO+QCu931+omoPeNzBfQVfI70qO 3WmqfPazewpMi4dit5oXP4/cMfC4mRmqgTc+Ib1ioFQZs4Q3EX93hKJ/kXOw== Original-Received: from acm.muc.de (pd953a405.dip0.t-ipconnect.de [217.83.164.5]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Mon, 28 Aug 2023 23:46:47 +0200 Original-Received: (qmail 6477 invoked by uid 1000); 28 Aug 2023 21:46:46 -0000 Content-Disposition: inline In-Reply-To: X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de Received-SPF: pass client-ip=193.149.48.3; envelope-from=acm@muc.de; helo=mail.muc.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: 2.1.29 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-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:309458 Archived-At: Hello, Ulrich. On Mon, Aug 28, 2023 at 23:01:53 +0200, Ulrich Mueller wrote: > >>>>> On Mon, 28 Aug 2023, Alan Mackenzie wrote: > >> > (when (< emacs-major-version 24) > >> > (defadvice .....)) > >> I believe (eval-when-compile (< emacs-major-version 24)) would work? > > I've twisted my head into knots in the past trying to work out how to > > use eval-when/and-compile for this purpose. The point is, I don't want > > the defadvice to be evaluated at compile time; I just want it to be > > compiled (or not). > Sorry, I should have been clearer. The full construct would look like > this: > (when (eval-when-compile (< emacs-major-version 24)) > (defadvice .....)) Ah! So the eval-when-compile gets compiled to a constant nil or t, and the byte compiler optimises the test of this out, either compiling or not compiling the (defadvice .....). Thanks! I hadn't been aware of that little detail. > So only the test would be evaluated at compile time, the defadvice > itself would be compiled normally (or not, if the test fails). However, when evaluating the containing defun/defmacro rather than byte compiling it, the irritating warning message will appear with the e-w-c strategem, but not with hash-if. ;-) -- Alan Mackenzie (Nuremberg, Germany).