From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Lexical binding: why? Date: Tue, 28 May 2019 17:41:27 +0000 Message-ID: <20190528174127.GC5296@ACM> References: <20190528100850.GA5296@ACM> <20190528134451.GB5296@ACM> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="227480"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.10.1 (2018-07-13) Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue May 28 19:43:31 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hVg8J-000x3C-3h for ged-emacs-devel@m.gmane.org; Tue, 28 May 2019 19:43:31 +0200 Original-Received: from localhost ([127.0.0.1]:40311 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVg8H-0003kD-IV for ged-emacs-devel@m.gmane.org; Tue, 28 May 2019 13:43:29 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:44577) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVg7M-0003j2-Cl for emacs-devel@gnu.org; Tue, 28 May 2019 13:42:33 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hVg7L-0007bM-Gx for emacs-devel@gnu.org; Tue, 28 May 2019 13:42:32 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:56816 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1hVg7J-00074j-EF for emacs-devel@gnu.org; Tue, 28 May 2019 13:42:31 -0400 Original-Received: (qmail 43999 invoked by uid 3782); 28 May 2019 17:41:28 -0000 Original-Received: from acm.muc.de (p4FE15C8D.dip0.t-ipconnect.de [79.225.92.141]) by colin.muc.de (tmda-ofmipd) with ESMTP; Tue, 28 May 2019 19:41:27 +0200 Original-Received: (qmail 7429 invoked by uid 1000); 28 May 2019 17:41:27 -0000 Content-Disposition: inline In-Reply-To: X-Delivery-Agent: TMDA/1.1.12 (Macallan) X-Primary-Address: acm@muc.de X-detected-operating-system: by eggs.gnu.org: FreeBSD 9.x [fuzzy] X-Received-From: 193.149.48.1 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:237114 Archived-At: Hello, Stefan. On Tue, May 28, 2019 at 13:21:22 -0400, Stefan Monnier wrote: > > Just in passing2, it seems to be difficult to enable lexical binding > > conditionally. The best that I can come up with is something like: > > -*- eval: (setq lexical-binding (> emacs-major-version 25)) -*- > Hmm... why do you need that? Is that because of a performance problem > in Emacs-24's lexical-binding support (likely the one that affects > condition-case and friends)? I was thinking more of a bug, since fixed, in older versions of the lexical-binding code. Purely hypothetically at the moment, of course. But this code is surely not so simple that bugs can be ruled out. But performance problems in older versions of l-b would also be a reason. For consistency with other features, which can all be enabled conditionally, surely lexical-binding should also be conditionally enablable in a reasonable way. > Stefan -- Alan Mackenzie (Nuremberg, Germany).