From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? Date: Thu, 2 Jul 2020 16:51:03 +0200 Message-ID: <6CF8EE58-9A49-40E7-AA86-48AB39BF94BA@acm.org> References: <3A9CC2A3-8307-47B2-8D80-795C0AF020E1@acm.org> <0433A879-C98D-4B1A-B85C-A15DA9289099@acm.org> <1621669100.2102667.1593639091621@mail.yahoo.com> <775819003.2516724.1593687594435@mail.yahoo.com> <5F2B4684-34D1-4474-8909-9F435369FE54@acm.org> <705260433.2731607.1593698199171@mail.yahoo.com> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.14\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="39796"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Paul Eggert , Stefan Monnier , 42147@debbugs.gnu.org To: Andrea Corallo Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Thu Jul 02 16:52:13 2020 Return-path: Envelope-to: geb-bug-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 1jr0ZO-000ADA-Qp for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 02 Jul 2020 16:52:10 +0200 Original-Received: from localhost ([::1]:34336 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jr0ZN-0003XZ-Pr for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 02 Jul 2020 10:52:09 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:33632) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jr0ZG-0003XO-IH for bug-gnu-emacs@gnu.org; Thu, 02 Jul 2020 10:52:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:43955) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jr0ZG-0004kY-9R for bug-gnu-emacs@gnu.org; Thu, 02 Jul 2020 10:52:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1jr0ZG-0000yz-65 for bug-gnu-emacs@gnu.org; Thu, 02 Jul 2020 10:52:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Thu, 02 Jul 2020 14:52:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 42147 X-GNU-PR-Package: emacs Original-Received: via spool by 42147-submit@debbugs.gnu.org id=B42147.15937014853731 (code B ref 42147); Thu, 02 Jul 2020 14:52:02 +0000 Original-Received: (at 42147) by debbugs.gnu.org; 2 Jul 2020 14:51:25 +0000 Original-Received: from localhost ([127.0.0.1]:55501 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jr0Ye-0000y5-NP for submit@debbugs.gnu.org; Thu, 02 Jul 2020 10:51:24 -0400 Original-Received: from mail1435c50.megamailservers.eu ([91.136.14.35]:56118 helo=mail263c50.megamailservers.eu) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jr0Yb-0000xr-VL for 42147@debbugs.gnu.org; Thu, 02 Jul 2020 10:51:23 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1593701467; bh=S/WWDQln/Z5lIpubRLuuCmORemJZCo2nQJYzWM8OwSo=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=MB4ACAPqi9wpcmdOhsnw5mhm+st1Dff+dBFKjVkti51OasVy2+eKJ7OaUFdxzrRrU 0+R+Cdj54itK+gQz6kIqYb4P9V3Z/VyJqicIZnbTcYFQqfXZC+i2+1kY+PdSkcAy2O qf/sfCTRswGdUBXPOV9Q+DNpmeEKkYemyQ0gzVKE= Feedback-ID: mattiase@acm.or Original-Received: from [192.168.0.4] (c188-150-171-71.bredband.comhem.se [188.150.171.71]) (authenticated bits=0) by mail263c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 062Ep3Wo002570; Thu, 2 Jul 2020 14:51:05 +0000 In-Reply-To: <705260433.2731607.1593698199171@mail.yahoo.com> X-Mailer: Apple Mail (2.3445.104.14) X-CTCH-RefID: str=0001.0A782F26.5EFDF45B.0033, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-CSC: 0 X-CHA: v=2.3 cv=e6d4tph/ c=1 sm=1 tr=0 a=SF+I6pRkHZhrawxbOkkvaA==:117 a=SF+I6pRkHZhrawxbOkkvaA==:17 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=LW-2j2PazT-2T_-krbcA:9 a=CjuIK1q_8ugA:10 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:182637 Archived-At: 2 juli 2020 kl. 15.56 skrev Andrea Corallo : > Well is cons allocation a semantically visible effect then? How is it > different? Conses are mutable and thus each have their own identity. Numbers are = immutable and have none; there is no defined way to distinguish two = numbers that have the same value ('eq' does not give well-defined = results). The compiler is free to, and does, deduplicate equal bignums. = For instance, try (disassemble (lambda () (list 18723645817263338474859 = 18723645817263338474859))) and you will see that the resulting code will only contain one instance = of the number. > I thought the reason why cons is not constant folded is to respect the > allocation side effect, at least that's what I convinced my-self of :) Yes, in the sense that (defun f () (cons 'a 'b)) produces a fresh (a . b) each time (f) is called, because the returned = values can be distinguished both explicitly by 'eq' and by mutating it = and observing whether the change affects previously returned values or = not. Neither works for numbers.