From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: member returns list (was: Re: To `boundp' or not to `boundp'?) Date: Wed, 02 Sep 2015 23:35:30 +0200 Message-ID: <87vbbsjyhp.fsf@debian.uxu> References: <55E5C99B.3020608@yandex.ru> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1441229822 25947 80.91.229.3 (2 Sep 2015 21:37:02 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 2 Sep 2015 21:37:02 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Wed Sep 02 23:36:53 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 1ZXFi2-0004jC-J4 for geh-help-gnu-emacs@m.gmane.org; Wed, 02 Sep 2015 23:36:46 +0200 Original-Received: from localhost ([::1]:41675 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFi2-0004Vw-Vq for geh-help-gnu-emacs@m.gmane.org; Wed, 02 Sep 2015 17:36:46 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:55291) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFhP-0003vw-SK for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:36:11 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZXFhM-00072i-1K for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:36:07 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:59555) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFhL-00072K-RC for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:36:03 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZXFgw-000412-7z for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 23:35:38 +0200 Original-Received: from nl106-137-244.student.uu.se ([130.243.137.244]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 02 Sep 2015 23:35:38 +0200 Original-Received: from embe8573 by nl106-137-244.student.uu.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 02 Sep 2015 23:35:38 +0200 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Original-Lines: 37 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: nl106-137-244.student.uu.se Mail-Copies-To: never User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) Cancel-Lock: sha1:G5lnUa+bBG3/dHb2WkwK5L1JNhc= 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:106994 Archived-At: Barry Margolin writes: > It could be useful for something like > > (length (member item list)) > > Or it could be used in a loop, where you repeat the > operation with the list that it returned. Yes, I understand it can be used in many situations. The sky is the limit. What I thought, I thought it was either an "inverted optimization" (i.e., the optimization is not to make it intuitive but leave it as it is which is faster and works the same) *or* if there was one (1), or but a few cases where it is very useful, simple combinations like the 1-2 of boxing or one-timer in ice hockey, that would be interesting to see. We can compare it to something else and you will understand immediately what I mean: `or' is intuitively a boolean, but in practice it is a boolean AND the item which was first found to be true, returned. I.e., it is just like `member' in that sense. However, with `or' if anyone asked the question I asked about `member', I would answer without blinking, because then you can do (or title "The boring standard title that should never appear") The examples provided hasn't been as straightforward as that, at least not to me, but it is OK. They don't have to be. -- underground experts united http://user.it.uu.se/~embe8573