From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Andrea Corallo Newsgroups: gmane.emacs.devel Subject: Re: A prototype for a binding based approach to proper namespaces Date: Sat, 09 May 2020 15:50:31 +0000 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="48981"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) Cc: emacs-devel@gnu.org To: Daniel Colascione Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat May 09 17:51:20 2020 Return-path: Envelope-to: ged-emacs-devel@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 1jXRl1-000CeI-Ii for ged-emacs-devel@m.gmane-mx.org; Sat, 09 May 2020 17:51:19 +0200 Original-Received: from localhost ([::1]:43368 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jXRl0-0002zW-4L for ged-emacs-devel@m.gmane-mx.org; Sat, 09 May 2020 11:51:18 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:46616) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jXRkL-0001yz-7Q for emacs-devel@gnu.org; Sat, 09 May 2020 11:50:37 -0400 Original-Received: from mx.sdf.org ([205.166.94.20]:51888) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jXRkJ-0001eK-Ij for emacs-devel@gnu.org; Sat, 09 May 2020 11:50:36 -0400 Original-Received: from sdf.org (ma.sdf.org [205.166.94.33]) by mx.sdf.org (8.15.2/8.14.5) with ESMTPS id 049FoV96002386 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits) verified NO); Sat, 9 May 2020 15:50:31 GMT Original-Received: (from akrl@localhost) by sdf.org (8.15.2/8.12.8/Submit) id 049FoVgM012705; Sat, 9 May 2020 15:50:31 GMT In-Reply-To: (Daniel Colascione's message of "Sat, 09 May 2020 08:16:17 -0700") Received-SPF: pass client-ip=205.166.94.20; envelope-from=akrl@sdf.org; helo=mx.sdf.org X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/09 11:50:32 X-ACL-Warn: Detected OS = ??? X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:249479 Archived-At: Daniel Colascione writes: >> I think it depends on how resilient you want to have your language to >> redefinitions. Say you have four libraries B derived from A and C from >> B etc: >> >> A <= B <= C <= > > > We don't have these problems at all with an approach based on symbol > rewriting in the reader. Even one additional pointers chase at runtime > is too much, especially since we're considering using this mechanism > as a routine way to access module provided facilities and not as a > rare patch for papering over other problems, as with existing symbol > aliases. (Thanks to modern memory architectures, each pointer chase is > brutal.) Yes, I dislike reader magic, but I dislike runtime overhead a > lot more. I agree with you in principle, but the fact that a pointer chase more is negative for performance in a measurable way or not for this case should be verified with a measure. Cache misses in modern architectures can be expansive but also caches are now very big. I'm pretty sure that if you have a good locality on bindings given we often hit there cache misses should't be much of a problem. I'm sure you know it but for public record: this argument obviously applies to global variables only, locals in lexical code are not effected. >> E has visibility on ~everything was defined in A. Now what if while >> running A changes the value of something used by E? We need at least >> one indirection to handle that otherwise you would be pointing still to >> the original object. But it is more complex because while running B >> could decide to unimport the definition from A and define the variable >> locally, > > Why should we support this kind of post definition namespace modification? I think is good to support it not to have to restart Emacs while developing. Python restarts all the time, Emacs depends on the user habit :) Andrea -- akrl@sdf.org