From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Change in files.el Date: Sat, 28 Jan 2017 10:40:41 -0500 Message-ID: References: <83mvebzh0k.fsf@gnu.org> <83bmurz0y9.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1485618083 1371 195.159.176.226 (28 Jan 2017 15:41:23 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 28 Jan 2017 15:41:23 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sat Jan 28 16:41:19 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cXV7l-0007en-Pn for ged-emacs-devel@m.gmane.org; Sat, 28 Jan 2017 16:41:09 +0100 Original-Received: from localhost ([::1]:52288 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cXV7r-0000JA-01 for ged-emacs-devel@m.gmane.org; Sat, 28 Jan 2017 10:41:15 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:36226) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cXV7k-0000Ir-Qw for emacs-devel@gnu.org; Sat, 28 Jan 2017 10:41:09 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cXV7h-00073B-Dc for emacs-devel@gnu.org; Sat, 28 Jan 2017 10:41:08 -0500 Original-Received: from [195.159.176.226] (port=49754 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cXV7h-00072v-74 for emacs-devel@gnu.org; Sat, 28 Jan 2017 10:41:05 -0500 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1cXV7S-00066m-So for emacs-devel@gnu.org; Sat, 28 Jan 2017 16:40:50 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 25 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:RyyDNzGCvCFgj9YloMMsYwk8RXg= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 195.159.176.226 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:211699 Archived-At: >> - So that you don't have to wrap each and every use inside an `if'. >> - Or so you don't have to fix the docstring to say what happens when the >> value is nil. >> - Or so you can use `add-function' on it. >> - More generally, so that you can slightly change its behavior without >> having to re-implement the default behavior by hand. >> - Also, so as to make sure that it is *possible* to reimplement the >> default behavior by hand (i.e. to make sure the predicate has access to all >> the info it needs to reproduce the default behavior). > These sound minor to me (and the last two are also possible without > the requirement, AFAIU). Hmm... how do you get the last two without that requirement? > By contrast, insisting on a function value instead of the default nil > forces me to go through at least one more level of indirection when > I need to understand what happens in a function that references such > variables, which sounds like a more serious trouble from my POV. I don't follow, sorry. I don't understand what you mean by "go through at least one more level of indirection" here. Could you explain with an example. Stefan