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: why are there [v e c t o r s] in Lisp? Date: Sat, 17 Oct 2015 01:47:23 +0200 Message-ID: <877fmmpe9g.fsf@debian.uxu> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1445038845 13678 80.91.229.3 (16 Oct 2015 23:40:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 16 Oct 2015 23:40:45 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sat Oct 17 01:40:35 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 1ZnEbu-0006UQ-He for geh-help-gnu-emacs@m.gmane.org; Sat, 17 Oct 2015 01:40:30 +0200 Original-Received: from localhost ([::1]:56336 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZnEbt-0002MT-Ma for geh-help-gnu-emacs@m.gmane.org; Fri, 16 Oct 2015 19:40:29 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:54634) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZnEbb-0002KT-5Z for help-gnu-emacs@gnu.org; Fri, 16 Oct 2015 19:40:12 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZnEbX-0006Hl-5O for help-gnu-emacs@gnu.org; Fri, 16 Oct 2015 19:40:11 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:35268) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZnEbW-0006HS-VN for help-gnu-emacs@gnu.org; Fri, 16 Oct 2015 19:40:07 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZnEbS-0005wg-TQ for help-gnu-emacs@gnu.org; Sat, 17 Oct 2015 01:40:02 +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 ; Sat, 17 Oct 2015 01:40:02 +0200 Original-Received: from embe8573 by nl106-137-244.student.uu.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 17 Oct 2015 01:40:02 +0200 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Original-Lines: 29 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:StvkkRMgmhEkOMz20DdApmhTqxA= 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:107684 Archived-At: Barry Margolin writes: > Lists and vectors have different performance > characteristics. With lists, it's easy to insert and > delete elements anywhere in the sequence, you just > add another cons in the cdr chain, but accessing the > nth element is O(n). With vectors, inserting and > deleting is expensive, because you have to shift all > the following elements over to make room (and > appending may require moving the whole thing, > because you didn't allocate enough room in the > original location), but accessing the nth element > can be done in constant time. > > So lists are good for flexible data structures that > you typically access linearly, while vectors are > good for random-access data. Also, because vectors > are stored in contiguous memory, they generally > exhibit better locality -- this was more important > in the days when RAM was expensive and limited, > because paging was more likely when you had a large > working set. Right, the international press is happy with this answer. -- underground experts united http://user.it.uu.se/~embe8573