From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Thierry Volpiatto Newsgroups: gmane.emacs.help Subject: Re: how to access a large datastructure efficiently? Date: Thu, 04 Mar 2010 07:59:41 +0100 Organization: ThierryVolpiatto Message-ID: <873a0gshb6.fsf@tux.homenetwork> References: NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: dough.gmane.org 1267686305 31658 80.91.229.12 (4 Mar 2010 07:05:05 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Thu, 4 Mar 2010 07:05:05 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Mar 04 08:04:58 2010 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Nn57A-00029r-DV for geh-help-gnu-emacs@m.gmane.org; Thu, 04 Mar 2010 08:04:56 +0100 Original-Received: from localhost ([127.0.0.1]:35378 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nn579-0000Th-O2 for geh-help-gnu-emacs@m.gmane.org; Thu, 04 Mar 2010 02:04:55 -0500 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nn56W-0000Tc-4O for help-gnu-emacs@gnu.org; Thu, 04 Mar 2010 02:04:16 -0500 Original-Received: from [140.186.70.92] (port=56171 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nn56Q-0000TU-Jk for help-gnu-emacs@gnu.org; Thu, 04 Mar 2010 02:04:14 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Nn56O-0008NG-Sj for help-gnu-emacs@gnu.org; Thu, 04 Mar 2010 02:04:10 -0500 Original-Received: from lo.gmane.org ([80.91.229.12]:34726) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Nn56O-0008NC-G6 for help-gnu-emacs@gnu.org; Thu, 04 Mar 2010 02:04:08 -0500 Original-Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1Nn56N-0001qN-GP for help-gnu-emacs@gnu.org; Thu, 04 Mar 2010 08:04:07 +0100 Original-Received: from 43.211.85-79.rev.gaoland.net ([79.85.211.43]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 04 Mar 2010 08:04:07 +0100 Original-Received: from thierry.volpiatto by 43.211.85-79.rev.gaoland.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 04 Mar 2010 08:04:07 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 38 Original-X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: 43.211.85-79.rev.gaoland.net Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAElBMVEUHBARgJRFPS0WbMBTC TSG/uJs0yyVHAAAACXBIWXMAAAsSAAALEgHS3X78AAAACXZwQWcAAAAwAAAAMADO7oxXAAABpUlE QVQ4y3VTQXKDMAyUnD7AwvQOhtxj5N4LFh9ow/+/UtlpM0BczWSS0Wola7UBeEb3+3kJ/5p9ZLz3 UI0n0J0Y4K/lh1nG24FhlJOR2LdSKtpV5gfi/Zd+NdaJBbB4D5N0JnfUIVp6obZURkJwS2a8b9uX AkgxA5gCEcknAH1s2z0DPooWmjGKcJR+HNZt+9bm0GtGRycRuZGs98Ffr02vABWGopIAhmXmxnQN BwBXZjgFLHRoqbfeYxCLWqsjLyKhbEHW+A5nEs699Q2O80ALrgHTmUTy6P0MnKyKQpKHpoNWokxs F0D5VegvWmEozyE6nuMiS98mWzlUQ9bW8qYfqOaFtzWlYCqGeIs6HEyl08jkrxUG9MF5ipXpOOpd ZMoXPPVSLWJiiwNNB+eRSyxJZmQKcacikgucnCRiHuJOLmyYJRDPwOqAvY4pA+Wy+VS8G26BAsdb Ph2Hw7ORy/H0IOG0TnaM8Cp0XrFYyU0v2z8AqkifPVbLZ0qo/gsRg60C7p+8Ov9jrUIxFde+jnAq X42hyp/c+ZcnVyUYBarrqZt3+R8450png3cWKgAAACV0RVh0ZGF0ZTpjcmVhdGUAMjAwOC0wNS0z MVQyMjoxNDoyMiswMjowMK3VBDcAAAAldEVYdGRhdGU6bW9kaWZ5ADIwMDctMTAtMjhUMTc6MDg6 NDgrMDE6MDDLdIcLAAAAEXRFWHRqcGVnOmNvbG9yc3BhY2UAMix1VZ8AAAAgdEVYdGpwZWc6c2Ft cGxpbmctZmFjdG9yADJ4MiwxeDEsMXgxSfqmtAAAAABJRU5ErkJggg== User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.93 (gnu/linux) Cancel-Lock: sha1:rWTUK+5ZIy+8WIzk/cR5hp/jLuA= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:72351 Archived-At: Hi, Christian Wittern writes: > Hi there, > > Here is the problem I am trying to solve: > > I have a large list of items which I want to access. The items are in > sequential order, but many are missing in between, like: > > (1 8 17 23 25 34 45 47 50) [in reality, there is a value associated > with this, but I took it out for simplicity] > > Now when I am trying to access with a key that is not in the list, I > want to have the one with the closest smaller key returned, so for 6 > and 7 this would be 1, but for 8 and 9 this would be 8. > > Since the list will have thousands of elements, I do not want to simply > loop through it but am looking for better ways to do this in Emacs lisp. > Any ideas how to achieve this? ,---- | (defun closest-elm-in-seq (n seq) | (let ((pair (loop with elm = n with last-elm | for i in seq | if (and last-elm (< last-elm elm) (> i elm)) return (list last-elm i) | do (setq last-elm i)))) | (if (< (- n (car pair)) (- (cadr pair) n)) | (car pair) (cadr pair)))) `---- That return the closest, but not the smaller closest, but it should be easy to adapt. -- Thierry Volpiatto Gpg key: http://pgp.mit.edu/