From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Pascal J. Bourguignon" Newsgroups: gmane.emacs.help Subject: Re: 'length' function for lists and cons cells? Date: Thu, 21 Mar 2013 21:49:23 +0100 Organization: Informatimago Message-ID: <87sj3opjfw.fsf@kuiper.lan.informatimago.com> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1363912331 22528 80.91.229.3 (22 Mar 2013 00:32:11 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 22 Mar 2013 00:32:11 +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 Mar 22 01:32:35 2013 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 1UIpuM-0005hO-GG for geh-help-gnu-emacs@m.gmane.org; Fri, 22 Mar 2013 01:32:34 +0100 Original-Received: from localhost ([::1]:39701 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIptz-0008D6-6I for geh-help-gnu-emacs@m.gmane.org; Thu, 21 Mar 2013 20:32:11 -0400 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 45 Original-X-Trace: individual.net PR0n64/c3SfEEFpWa+DxtgFZuNxjfCU+wSjvUoG9wxWokTUMVl Cancel-Lock: sha1:MmJkZDM4NzZjMWFmZDQ1YWRiOTAzNTdiMDc2MDYzOTIzYTYzZjllZg== sha1:BtacQ0UKnoTisZHcPFUI8xTOCD8= Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:197368 X-Mailman-Approved-At: Thu, 21 Mar 2013 20:28:22 -0400 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:89650 Archived-At: Thorsten Jolitz writes: > Hi List, > > which function could I use when I map an alist e.g. with dolist, that > contains both types of associations as shown below: cons cells, or lists > with 3 or more elements? > > 'length' doesn't work on cons cells: > > ,------------------------ > | (length '("a" "b" "c")) > | 3 > `------------------------ > > ,-------------------------------------------------------------- > | (length '("a" . "c")) > | > | Debugger entered--Lisp error: (wrong-type-argument listp "c") > | length(("a" . "c")) > `-------------------------------------------------------------- I don't understand what you want to do. You can use length and dolist on alists and it will work perfectly: (length '((a . 1) (b . 2) (c . 3))) --> 3 (dolist (entry '((a . 1) (b . 2) (c . 3))) (destructuring-bind (key . value) entry (insert (format "key = %S, value = %S\n" key value)))) key = a, value = 1 key = b, value = 2 key = c, value = 3 If you want to count the cons cells, then why stop at the dotted-lists? There are also circular lists. See how you can do it at: https://gitorious.org/com-informatimago/com-informatimago/blobs/master/common-lisp/cesarum/list.lisp#line303 (note: this is Common Lisp, some translation to emacs lisp is needed (mostly, remove the colons from the loop keywords)). -- __Pascal Bourguignon__ http://www.informatimago.com/ A bad day in () is better than a good day in {}.