From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: expose XHASH [patch] Date: Thu, 31 Mar 2016 17:52:51 -0400 Message-ID: References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1459461209 1006 80.91.229.3 (31 Mar 2016 21:53:29 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 31 Mar 2016 21:53:29 +0000 (UTC) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Mar 31 23:53:20 2016 Return-path: Envelope-to: ged-emacs-devel@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 1alkWl-00056l-7O for ged-emacs-devel@m.gmane.org; Thu, 31 Mar 2016 23:53:19 +0200 Original-Received: from localhost ([::1]:34641 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alkWk-0005nr-P5 for ged-emacs-devel@m.gmane.org; Thu, 31 Mar 2016 17:53:18 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:49656) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alkWX-0005nk-BS for emacs-devel@gnu.org; Thu, 31 Mar 2016 17:53:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alkWU-0008PA-6F for emacs-devel@gnu.org; Thu, 31 Mar 2016 17:53:05 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:37879) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alkWT-0008Ox-Vr for emacs-devel@gnu.org; Thu, 31 Mar 2016 17:53:02 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1alkWS-0004zR-MC for emacs-devel@gnu.org; Thu, 31 Mar 2016 23:53:00 +0200 Original-Received: from 69-165-138-79.dsl.teksavvy.com ([69.165.138.79]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Mar 2016 23:53:00 +0200 Original-Received: from monnier by 69-165-138-79.dsl.teksavvy.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Mar 2016 23:53:00 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 26 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: 69-165-138-79.dsl.teksavvy.com User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) Cancel-Lock: sha1:44P4b34PD6K2+YbD514JdnBlvl8= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:202539 Archived-At: > Please don't write that the example is stupid, it is just an > example after all. FWIW, I have bumped into various cases where I also needed to define a hash for an equality function that's defined for example as (and (eq (car x) (car y)) (eq (cdr x) (cdr y))). Worse yet: you say that "sxhash _will_ work" but in reality it won't if the objects are later modified by side-effects. See for example: (cl--generic-with-memoization ;; FIXME: Since the fields of `generic' are modified, this ;; hash-table won't work right, because the hashes will change! ;; It's not terribly serious, but reduces the effectiveness of ;; the table. (gethash (cons generic methods) cl--generic-combined-method-memoization) from cl-generic.el. I wrote "It's not terribly serious", but IIRC there can be cases where it causes real problems. So a big "yes please" from me. Stefan