From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Save `nil' from the mutant void, preserve the truth of falsehood, prevent the falsehood of truth Date: Sun, 12 Sep 2010 16:00:15 +0200 Message-ID: References: NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: dough.gmane.org 1284300033 23646 80.91.229.12 (12 Sep 2010 14:00:33 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Sun, 12 Sep 2010 14:00:33 +0000 (UTC) Cc: emacs-devel@gnu.org To: MON KEY Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Sep 12 16:00:31 2010 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Oun6b-0003f6-8Y for ged-emacs-devel@m.gmane.org; Sun, 12 Sep 2010 16:00:29 +0200 Original-Received: from localhost ([127.0.0.1]:51704 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Oun6a-0003KN-GI for ged-emacs-devel@m.gmane.org; Sun, 12 Sep 2010 10:00:28 -0400 Original-Received: from [140.186.70.92] (port=39834 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Oun6T-0003I6-RX for emacs-devel@gnu.org; Sun, 12 Sep 2010 10:00:22 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Oun6S-0003Si-BM for emacs-devel@gnu.org; Sun, 12 Sep 2010 10:00:21 -0400 Original-Received: from impaqm5.telefonica.net ([213.4.138.5]:14137) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Oun6S-0003SO-1M for emacs-devel@gnu.org; Sun, 12 Sep 2010 10:00:20 -0400 Original-Received: from IMPmailhost5.adm.correo ([10.20.102.126]) by IMPaqm5.telefonica.net with bizsmtp id 5k771f00H2jdgqJ3Rq0HGP; Sun, 12 Sep 2010 16:00:17 +0200 Original-Received: from ceviche.home ([83.61.39.212]) by IMPmailhost5.adm.correo with BIZ IMP id 5q0F1f0024aeRwb1lq0Ggq; Sun, 12 Sep 2010 16:00:17 +0200 X-Brightmail-Tracker: AAAAAA== X-TE-authinfo: authemail="monnier$movistar.es" |auth_email="monnier@movistar.es" X-TE-AcuTerraCos: auth_cuTerraCos="cosuitnetc01" Original-Received: by ceviche.home (Postfix, from userid 20848) id 2DE22660D2; Sun, 12 Sep 2010 16:00:15 +0200 (CEST) In-Reply-To: (MON KEY's message of "Sat, 11 Sep 2010 19:33:07 -0400") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:130014 Archived-At: > Two one-liners not even a Perl devotee could love: > (prog1 #1=(fboundp ()) (unintern #1#)) Let's see how many lines of defenses you broke in the above code: - use of #1= in code: very bad. - unintern takes a symbol as argument, not a boolean, so it should not be called with the return value of (fboundp ...) - calling unintern without an obarray arg is a bad idea. Maybe we should make the second argument mandatory. > Sometimes, I'm able to recover `nil' long enough to save the session, > but even then i've not any reasonable surety that the busted `nil' is > a correct `nil'. The real nil is safely stored in a C variable `Qnil' which you should be able to get via something like (not t). But I don't think Elisp lets you re-intern it, since `intern' only takes a string rather than a symbol. Stefan