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 Date: Wed, 02 Sep 2015 23:47:12 +0200 Message-ID: <87pp20jxy7.fsf@debian.uxu> References: <55E5C99B.3020608@yandex.ru> <87lhcpu2wb.fsf_-_@debian.uxu> <874mjchisl.fsf@web.de> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1441230479 3403 80.91.229.3 (2 Sep 2015 21:47:59 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 2 Sep 2015 21:47:59 +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 23:47:46 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 1ZXFsf-0005pf-AR for geh-help-gnu-emacs@m.gmane.org; Wed, 02 Sep 2015 23:47:45 +0200 Original-Received: from localhost ([::1]:41773 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFsf-0003IV-Vi for geh-help-gnu-emacs@m.gmane.org; Wed, 02 Sep 2015 17:47:45 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:58072) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFsO-0003F3-8v for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:47:29 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZXFsK-0003Tf-Sd for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:47:28 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:33152) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXFsK-0003TU-Lf for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 17:47:24 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZXFsE-0005T7-BU for help-gnu-emacs@gnu.org; Wed, 02 Sep 2015 23:47:18 +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 23:47:18 +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 23:47:18 +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: sha1:3GYKPqFJHbBafDdPl44QwA/qT7g= 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:106995 Archived-At: Michael Heerdegen writes: > The `car' of the result of `member' is the actual > element you were searching. Since `member' tests > with `equal', that can be a different object. OK, so the `car' is the object, however ELT is searched for with `equal', which compares objects' "structure and contents". An object obviously have the same structure and contents when compared to itself, but nonetheless two objects can have the same structure and contents in what case the `car' and ELT are identical but still two objects. Ha! I'm smart... So then, is there a "member-whatever" that doesn't use `equal' but one of the many other functions available to compare items? Is there a "member" to which you can provide this function yourself? > But `member' returns a whole sublist. This gives you > also a simple mean to modify a list, like in this > example: > > (let ((list '(1 2 3 4 5))) (let ((list1 (member 3 > list))) (when list1 (setcar list1 -3)) list)) > > ==> (1 2 -3 4 5) Yes, already mentioned but true nonetheless. It would be interesting to see what programs you guys write because I never did stuff like that. Perhaps in HPC with tons of data, or old-school batch "data processing", this type of stuff is/was legio? -- underground experts united http://user.it.uu.se/~embe8573