From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: How to quickly compare equality of structs ... Date: Mon, 06 May 2019 20:49:23 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="209045"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue May 07 02:49:51 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hNoIp-000sIk-1X for ged-emacs-devel@m.gmane.org; Tue, 07 May 2019 02:49:51 +0200 Original-Received: from localhost ([127.0.0.1]:36019 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hNoIn-0007fU-Tm for ged-emacs-devel@m.gmane.org; Mon, 06 May 2019 20:49:50 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:37674) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hNoIW-0007de-0q for emacs-devel@gnu.org; Mon, 06 May 2019 20:49:32 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hNoIV-0003Uc-8U for emacs-devel@gnu.org; Mon, 06 May 2019 20:49:31 -0400 Original-Received: from [195.159.176.226] (port=56276 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hNoIV-0003Td-1l for emacs-devel@gnu.org; Mon, 06 May 2019 20:49:31 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.89) (envelope-from ) id 1hNoIT-000rzA-0G for emacs-devel@gnu.org; Tue, 07 May 2019 02:49:29 +0200 X-Injected-Via-Gmane: http://gmane.org/ Cancel-Lock: sha1:Rzn9TJFikoe09+YsLlkSrdKgm70= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 195.159.176.226 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:236219 Archived-At: > This afternoon, I came across the Cantor's Pairing Function that can be used > to create a unique ID for each fake cursor. With that unique ID, I can > limit the quantity of comparisons .... > n = ((x + y)*(x + y + 1)/2) + y Not sure why you care about limiting the number of comparisons. Replacing two comparisons with one-comparison-plus-two-mults (and reducing the range of x and y to sqrt(MAXINT) along thre way) doesn't sound like much of a win. Stefan