From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Lisp primitives and their calling of the change hooks Date: Fri, 05 Jan 2018 16:08:31 +0200 Message-ID: <831sj4bdpc.fsf@gnu.org> References: <20180103124543.GA5435@ACM> <20180104155111.GB6846@ACM> <20180104211154.GC6846@ACM> <838tdcbxrb.fsf@gnu.org> <20180105114107.GA6954@ACM> <83373kbguy.fsf@gnu.org> <20180105133448.GB6954@ACM> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1515161305 15508 195.159.176.226 (5 Jan 2018 14:08:25 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 5 Jan 2018 14:08:25 +0000 (UTC) Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Alan Mackenzie Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Jan 05 15:08:20 2018 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 1eXSfR-0003OI-5x for ged-emacs-devel@m.gmane.org; Fri, 05 Jan 2018 15:08:17 +0100 Original-Received: from localhost ([::1]:41910 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXShO-0002Rp-Co for ged-emacs-devel@m.gmane.org; Fri, 05 Jan 2018 09:10:18 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:45649) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXSgI-0002Oq-Sr for emacs-devel@gnu.org; Fri, 05 Jan 2018 09:09:12 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eXSgF-0007Fu-LH for emacs-devel@gnu.org; Fri, 05 Jan 2018 09:09:10 -0500 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:58878) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXSgF-0007Fn-Gw; Fri, 05 Jan 2018 09:09:07 -0500 Original-Received: from [176.228.60.248] (port=4870 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1eXSgD-0002xG-Hj; Fri, 05 Jan 2018 09:09:07 -0500 In-reply-to: <20180105133448.GB6954@ACM> (message from Alan Mackenzie on Fri, 5 Jan 2018 13:34:48 +0000) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e 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:221616 Archived-At: > Date: Fri, 5 Jan 2018 13:34:48 +0000 > Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org > From: Alan Mackenzie > > On Fri, Jan 05, 2018 at 15:00:21 +0200, Eli Zaretskii wrote: > > > Date: Fri, 5 Jan 2018 11:41:07 +0000 > > > Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org > > > From: Alan Mackenzie > > > > The "complex primitive" case can be distinguised from the "atomic > > > primitive" case because either the call to `after-change-functions' > > > is missing (i.e. there are two consecutive calls to > > > `before-change-functions'), or in the first call to > > > `after-change-functions', `OLD-LEN' is less then `END' - `BEG' in > > > `before-change-functions'. > > > > The above leaves unsaid what happens when a "complex primitive" happens > > > to call b-c-f and a-c-f as though it were an "atomic primitive". > > > It also provides no way to know, up front, whether a given primitive > > I'm about to call, is one or the other. IMO, we need some way of > > doing that, if we want to document this distinction. > > Do we really need this level of detail? My idea was to enable users of > b-c-f and a-c-f to predict what they're going to be being hit with. > > There are two patterns of handling b/a-c-f, the "atomic" and the > "complex". My above proposal documents enough for somebody using > b/a-c-f to be able to handle the "atomic" and "complex" uses. > [...] > What am I missing here? Maybe it's me that is missing something. You first say above that you want to "enable users of b-c-f and a-c-f to predict what they're going to be being hit with", which is exactly my concern, but then provide a recipe that AFAIU only works post-factum, i.e. the user can only know whether they called an "atomic" or a "complex" primitive by analyzing the calls to the 2 hooks as result of calling the primitive. If that's indeed what you are saying, IMO it's not a useful criterion, because generally when I read documentation, I shouldn't be required to write code in order to interpret the documentation. > Why does that hacker need to know exactly what each buffer-changing > primitive does, or which falls into which category? Surely it is enough > that she handle the b/a-c-f calls appropriately. How can she handle these calls correctly unless she knows which of the hooks will be called by a given primitive, and whether these calls will be balanced? And if she doesn't need to know that, then why do we have to tell here these details about the 2 classes of primitives? IOW, accurate information is only useful if one knows exactly how to apply it to the practical case in hand.