From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Philipp Stephani Newsgroups: gmane.emacs.bugs Subject: bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations? Date: Mon, 10 Aug 2020 15:42:48 +0200 Message-ID: References: <3A9CC2A3-8307-47B2-8D80-795C0AF020E1@acm.org> <0433A879-C98D-4B1A-B85C-A15DA9289099@acm.org> <1621669100.2102667.1593639091621@mail.yahoo.com> <33C2E2C8-16A6-47A9-B3A4-8A5F43648E04@acm.org> <51FE77F3-CA05-459A-9601-9E1EEBC1E2FE@acm.org> <1213DD41-01F9-4605-8D32-D750B6CE2B35@acm.org> <81F989D1-3CC4-450B-89D6-E9C16F766277@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="20571"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= , Paul Eggert , Andrea Corallo , 42147@debbugs.gnu.org To: Stefan Monnier Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Mon Aug 10 15:49:24 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 1k58B1-0005FE-5K for geb-bug-gnu-emacs@m.gmane-mx.org; 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Juli 2020 um 22:39 Uhr schrieb Stefan Monnier : > > > Regarding package-get-version: perhaps we should drop the 'pure' property > > and just let callers wrap it in eval-when-compile? > > I'd rather not: the benefit is too subtle, I'd expect most users won't > know/bother to use `eval-when-compile` around it even though I'd expect > a vast majority of the uses can benefit from compile-time evaluation. > In contrast the cases where the impurity will get in the way > should be rare. Arguments relating to probabilities ("most users", "vast majority", "rare") don't really apply here, as the discussion is about correctness. A pure function must be pure 100% of the time, no exceptions allowed. `package-get-version' can't possibly be pure: it doesn't take any argument, so if it were pure, it would have to return a constant in the mathematical sense.