From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: jorge.alfaro-murillo@yale.edu (Jorge A. Alfaro-Murillo) Newsgroups: gmane.emacs.help Subject: Re: Why is booleanp defined this way? Date: Fri, 17 Apr 2015 16:49:59 -0400 Message-ID: <87egnio4y0.fsf@yale.edu> References: <87siby7au6.fsf@mbork.pl> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; format=flowed X-Trace: ger.gmane.org 1429303852 7320 80.91.229.3 (17 Apr 2015 20:50:52 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 17 Apr 2015 20:50:52 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Apr 17 22:50:44 2015 Return-path: Envelope-to: geh-help-gnu-emacs@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 1YjDDn-0006Oa-Hn for geh-help-gnu-emacs@m.gmane.org; Fri, 17 Apr 2015 22:50:43 +0200 Original-Received: from localhost ([::1]:43466 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YjDDm-0007tO-Ls for geh-help-gnu-emacs@m.gmane.org; Fri, 17 Apr 2015 16:50:42 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:44424) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YjDDR-0007tI-H0 for help-gnu-emacs@gnu.org; Fri, 17 Apr 2015 16:50:22 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YjDDM-00009f-Ih for help-gnu-emacs@gnu.org; Fri, 17 Apr 2015 16:50:21 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:58479) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YjDDM-00009M-C6 for help-gnu-emacs@gnu.org; Fri, 17 Apr 2015 16:50:16 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1YjDDD-0005y9-4B for help-gnu-emacs@gnu.org; Fri, 17 Apr 2015 22:50:07 +0200 Original-Received: from nat-130-132-173-151.central.yale.edu ([130.132.173.151]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 17 Apr 2015 22:50:07 +0200 Original-Received: from jorge.alfaro-murillo by nat-130-132-173-151.central.yale.edu with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 17 Apr 2015 22:50:07 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 20 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: nat-130-132-173-151.central.yale.edu User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:v3JrsDSu+nuh2Qwk7OmgjTxTiSc= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:103781 Archived-At: Marcin Borkowski writes: > Seemingly, it doesn't make much sense: what is the purpose of > saying > > (and (whatever) t) > > instead of just > > (whatever) > > for a predicate? Of course, this "normalizes" any "truthy" > value to "t", but is it really needed for anything (except > perhaps being elegant)? Perhaps so that it returns t instead of whatever, if whatever is not nil. -- Jorge.