From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: How to get plist properties list? Date: Tue, 12 Jan 2021 16:23:58 -0500 Message-ID: References: <7eec4142-3c37-4084-9ea1-73df5df2c821@default> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="36225"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:6cjaYNj56ZLvQdT4AMnlpPq2RoU= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Jan 12 22:24:28 2021 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kzR9Q-0009Jx-S3 for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 12 Jan 2021 22:24:28 +0100 Original-Received: from localhost ([::1]:60456 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kzR9P-0001t2-Uj for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 12 Jan 2021 16:24:27 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:41462) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kzR95-0001rE-AW for help-gnu-emacs@gnu.org; Tue, 12 Jan 2021 16:24:07 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]:51392) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kzR93-0007KH-No for help-gnu-emacs@gnu.org; Tue, 12 Jan 2021 16:24:07 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1kzR91-0008nd-Mk for help-gnu-emacs@gnu.org; Tue, 12 Jan 2021 22:24:03 +0100 X-Injected-Via-Gmane: http://gmane.org/ Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.23 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-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:127209 Archived-At: > (defun mutt-identity-signature (identity) > (let* ((sql (format "SELECT * FROM identities WHERE identities_id = %s" identity)) > (list (first (rcd-sql-list sql *cf*))) > (identity-id (elt list 0)) > (identity-name (elt list 1)) > (identity-first-name (elt list 2)) > (identity-last-name (elt list 3)) That's a completely different situation: the above code does not operate on a list of elements of arbitrary length, but on what is fundamentally a tuple of fixed length which just happens to be represented as a Lisp linked list. > (defun mapping/map-locations-point-kml-placemark (p) > (mapping/kml-placemark (elt p 3) (elt p 4) (list (elt p 0) (elt p 1) (elt p 2)))) Notice that the "n" passed to `elt` is a constant, whereas in the original code where I pointed out the problem: (dotimes (i length (reverse properties)) (if (divisible-by-2-or-0-p i) (push (elt plist i) properties))))) the argument to `elt` (here `i`) is not a constant. That changes the nature of the problem completely. (elt FOO 100) may be arguably slow, but it's still constant time, so it won't get slower when applied to a larger data-structure. In contrast (elt FOO i) will probably be fairly fast on small data structures, where `i` is small, but it will get slower and slower as `i` grows with the size of the data structure. Stefan