From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Lawrence Mitchell Newsgroups: gmane.emacs.bugs Subject: bug#7086: `booleanp' return value is multi-valued list Date: Fri, 24 Sep 2010 10:28:41 +0100 Message-ID: References: <83pqw4vpxv.fsf@gnu.org> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: dough.gmane.org 1285321280 24765 80.91.229.12 (24 Sep 2010 09:41:20 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Fri, 24 Sep 2010 09:41:20 +0000 (UTC) To: bug-gnu-emacs@gnu.org Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Fri Sep 24 11:41:18 2010 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1Oz4mL-0000Tw-FS for geb-bug-gnu-emacs@m.gmane.org; Fri, 24 Sep 2010 11:41:17 +0200 Original-Received: from localhost ([127.0.0.1]:43965 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Oz4mK-00044J-Pm for geb-bug-gnu-emacs@m.gmane.org; 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Fri, 24 Sep 2010 05:29:29 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Oz4as-0003qK-VO for bug-gnu-emacs@gnu.org; Fri, 24 Sep 2010 05:29:28 -0400 Original-Received: from lo.gmane.org ([80.91.229.12]:54635) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Oz4as-0003qE-Op for bug-gnu-emacs@gnu.org; Fri, 24 Sep 2010 05:29:26 -0400 Original-Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1Oz4ar-0003MW-6L for bug-gnu-emacs@gnu.org; Fri, 24 Sep 2010 11:29:25 +0200 Original-Received: from garnet.epcc.ed.ac.uk ([129.215.56.222]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 24 Sep 2010 11:29:25 +0200 Original-Received: from wence by garnet.epcc.ed.ac.uk with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 24 Sep 2010 11:29:25 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 52 Original-X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: garnet.epcc.ed.ac.uk User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (usg-unix-v) Cancel-Lock: sha1:I4gcTJ5IO640+n1Vumk0AH0ly5s= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.11 Precedence: list Resent-Date: Fri, 24 Sep 2010 05:27:01 -0400 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:40393 Archived-At: MON KEY wrote: > This one matters. It is the penultimate Emacs lisp predicate. > It tests for a boolean value yet it returns a list. Which you can happily dispatch on: (if (booleanp foo) (if (null foo) (do-something-if-foo-is-nil) (do-something-if-foo-is-t)) (do-something-if-foo-is-neither-nil-nor-t)) It's hard to see what else is required [...] > On Thu, Sep 23, 2010 at 4:12 AM, Eli Zaretskii wrote: [...] MON KEY claims that (funcall (lambda (x) (booleanp x))) giving an error is somehow problematic. >> Exactly! See the above node in the manual. >> But this has nothing to do with booleanp. > It has everything to do with it. These are just the types of > situations where interrogating a boolean is what is wanted. What? (funcall (lambda (x) (1+ x))) => (wrong-number-of-arguments (lambda (x) (1+ x)) 0) (funcall (lambda (x) (booleanp x))) => (wrong-number-of-arguments (lambda (x) (booleanp x)) 0) Calling a function expecting an argument without one is an error, irrespective of the function involved. Do you in fact want: (require 'cl) (defun* foo (&optional (x nil got-x-p)) (if got-x-p (do-something-if-x-was-an-argument x) (do-something-different))) [...] -- Lawrence Mitchell