From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Kelly Dean Newsgroups: gmane.emacs.devel Subject: Re: The purpose of makunbound Date: Wed, 18 Feb 2015 08:51:41 +0000 Message-ID: References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1424249613 23721 80.91.229.3 (18 Feb 2015 08:53:33 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 18 Feb 2015 08:53:33 +0000 (UTC) Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Feb 18 09:53:19 2015 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YO0Ni-0006SZ-Ha for ged-emacs-devel@m.gmane.org; Wed, 18 Feb 2015 09:53:18 +0100 Original-Received: from localhost ([::1]:49376 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YO0Nh-0001ZS-Kl for ged-emacs-devel@m.gmane.org; Wed, 18 Feb 2015 03:53:17 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:48671) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YO0Ne-0001ZN-Tx for emacs-devel@gnu.org; Wed, 18 Feb 2015 03:53:15 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YO0NX-0004vf-9Q for emacs-devel@gnu.org; Wed, 18 Feb 2015 03:53:14 -0500 Original-Received: from relay3-d.mail.gandi.net ([2001:4b98:c:538::195]:44223) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YO0NX-0004vP-3G for emacs-devel@gnu.org; Wed, 18 Feb 2015 03:53:07 -0500 Original-Received: from mfilter36-d.gandi.net (mfilter36-d.gandi.net [217.70.178.167]) by relay3-d.mail.gandi.net (Postfix) with ESMTP id 0D866A80B0; Wed, 18 Feb 2015 09:53:06 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at mfilter36-d.gandi.net Original-Received: from relay3-d.mail.gandi.net ([217.70.183.195]) by mfilter36-d.gandi.net (mfilter36-d.gandi.net [10.0.15.180]) (amavisd-new, port 10024) with ESMTP id cuOiFDTzZCB0; Wed, 18 Feb 2015 09:53:04 +0100 (CET) X-Originating-IP: 66.220.3.179 Original-Received: from localhost (gm179.geneticmail.com [66.220.3.179]) (Authenticated sender: kelly@prtime.org) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id 7D911A80AD; Wed, 18 Feb 2015 09:53:03 +0100 (CET) In-Reply-To: X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2001:4b98:c:538::195 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:183237 Archived-At: Stefan Monnier wrote: >> What's the use case of doing makunbound on a dynamically let-bound variable? > > What's the use case for disallowing it? Catching errors. If some code F does makunbound on a symbol that it assumes is currently used as the global variable, but F is called from some other code that dynamically let-binds the symbol, then F will accidentally set the dynamic variable to the special unboundedness value rather than unbind the global variable. If that's a bogus thing to do, then by disallowing it, the interpreter could catch the error. But if there's a legitimate use case for it, then of course it must be allowed. Is there one?