From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Andy Moreton Newsgroups: gmane.emacs.devel Subject: Re: Making 'eq' == 'eql' in bignum branch Date: Mon, 20 Aug 2018 22:54:09 +0100 Message-ID: <86k1okk8la.fsf@gmail.com> References: <29f933ac-a6bf-8742-66a7-0a9d6d3e5a88@disroot.org> <87lgaio7xd.fsf@tromey.com> <877em1cb0i.fsf@tromey.com> <765767b2-d2e5-a9a6-f724-d58ecf4847bb@cs.ucla.edu> <76081b5d-8c10-0a37-2c97-d4864c0faa80@cs.ucla.edu> <09153aed-361d-4f82-d9ac-b502314769ae@cs.ucla.edu> <861sato21d.fsf@gmail.com> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1534801991 27640 195.159.176.226 (20 Aug 2018 21:53:11 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 20 Aug 2018 21:53:11 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.50 (windows-nt) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 20 23:53:07 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1frs6k-000731-KS for ged-emacs-devel@m.gmane.org; Mon, 20 Aug 2018 23:53:06 +0200 Original-Received: from localhost ([::1]:49456 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1frs8p-0000ra-Ei for ged-emacs-devel@m.gmane.org; Mon, 20 Aug 2018 17:55:15 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:45693) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1frs84-0000rS-Fi for emacs-devel@gnu.org; Mon, 20 Aug 2018 17:54:29 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1frs81-0008AI-8V for emacs-devel@gnu.org; Mon, 20 Aug 2018 17:54:28 -0400 Original-Received: from [195.159.176.226] (port=47213 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1frs81-00089u-13 for emacs-devel@gnu.org; Mon, 20 Aug 2018 17:54:25 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1frs5o-0005vH-Iw for emacs-devel@gnu.org; Mon, 20 Aug 2018 23:52:08 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 49 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:8v+/IMSC+aiR+CYnZVqJAXyC0Ps= 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:228764 Archived-At: On Mon 20 Aug 2018, Pip Cet wrote: > On Mon, Aug 20, 2018 at 4:43 PM Andy Moreton wrote: >> On Mon 20 Aug 2018, Paul Eggert wrote: >> >> > Andy Moreton wrote: >> > >> >> There will always be a performance diffrence between fixnum and bignum >> >> values, and it may be useful for performance tuning to have a simple way >> >> to discover where that boundary lies. >> > >> > Performance nerds can use 'most-positive-fixnum' and 'most-negative-fixnum' >> > for that sort of thing. These constants have been there for some time and are >> > not going away. My objection is to 'bignump' and 'fixnump', which are no more >> > necessary as primitives than 'negativep' would be. >> >> Pip Cet was advocating removal of most-positive-fixnum, and that is what >> I was objecting to as being too severe. We do not need negativep as we >> already have other prmitives for testing that property. > > I'm sorry for the sloppy wording. `most-positive-fixnum' should stay: > it's an important implementation detail. All the references to it in > lisp/, though, look to me like they should be removed. Agreed, Apologies for misunderstanding your original message. > > I think keeping a Lisp function around for the sole purpose of testing > C code from Lisp is wrong. The right thing to do in this case is to > test the C code from C; I believe GCC does so extensively, and it > would be easy enough to add a test function that eassert()s that > FIXNUMP(Fsub1(Fadd1(MOST_POSITIVE_FIXNUM))), for example. A good point. > Again, I think important implementation details, like what a good > range for fast integer arithmetic is ([most-negative-fixnum, > most-positive-fixnum]) and how floats are encoded and whether IEEE > rules are being followed (IEEE_FLOATING_POINT), should be exposed to > Lisp. (For example, I'm playing around with big rational numbers, and > one possible implementation is for them to replace floats, but that > almost naturally requires a ratio-to-nearby-simple-ratio function to > avoid building up huge representations; whether to use such a function > and what it does would be an implementation detail, but one that code > might want to optimize for...) Perhaps these implementation details should also be added to bug reports ? AndyM