From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Using the GNU GMP Library for Bignums in Emacs Date: Wed, 18 Jul 2018 18:55:35 +0300 Message-ID: <831sc04jyg.fsf@gnu.org> References: <29f933ac-a6bf-8742-66a7-0a9d6d3e5a88@disroot.org> <83bmecy6fx.fsf@gnu.org> <0d3175d8-d996-651e-b221-71978bde3a65@cs.ucla.edu> <87tvpdnzgy.fsf@tromey.com> <4c2a814f-c254-29e5-39cf-11b5f2e5c9c8@cs.ucla.edu> <49d8ba62-c9a5-9203-d882-8e900b441ff3@cs.ucla.edu> <8e0320d9-e0d0-2b57-57cc-2df4399f133c@cs.ucla.edu> <87lgaio7xd.fsf@tromey.com> <877em1cb0i.fsf@tromey.com> <765767b2-d2e5-a9a6-f724-d58ecf4847bb@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1531929244 30892 195.159.176.226 (18 Jul 2018 15:54:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 18 Jul 2018 15:54:04 +0000 (UTC) Cc: tom@tromey.com, emacs-devel@gnu.org, monnier@IRO.UMontreal.CA, rms@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Jul 18 17:54:00 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 1ffom5-0007qj-Dy for ged-emacs-devel@m.gmane.org; Wed, 18 Jul 2018 17:53:57 +0200 Original-Received: from localhost ([::1]:37331 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ffooA-0006kM-KD for ged-emacs-devel@m.gmane.org; Wed, 18 Jul 2018 11:56:06 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:56686) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ffonw-0006iG-Ga for emacs-devel@gnu.org; Wed, 18 Jul 2018 11:55:53 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ffons-0006Fw-KI for emacs-devel@gnu.org; Wed, 18 Jul 2018 11:55:52 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:33361) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ffons-0006Fn-GU; Wed, 18 Jul 2018 11:55:48 -0400 Original-Received: from [176.228.60.248] (port=1275 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1ffonk-0001K3-9g; Wed, 18 Jul 2018 11:55:40 -0400 In-reply-to: <765767b2-d2e5-a9a6-f724-d58ecf4847bb@cs.ucla.edu> (message from Paul Eggert on Wed, 18 Jul 2018 03:20:40 -0700) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e 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:227548 Archived-At: > From: Paul Eggert > Date: Wed, 18 Jul 2018 03:20:40 -0700 > Cc: Tom Tromey , emacs-devel@gnu.org > > +/* Return true if X and Y are the same floating-point value. > + This looks at X's and Y's representation, since (unlike '==') > + it returns true if X and Y are the same NaN. */ > +static bool > +same_float (Lisp_Object x, Lisp_Object y) > +{ > + union double_and_words > + xu = { .val = XFLOAT_DATA (x) }, > + yu = { .val = XFLOAT_DATA (y) }; > + EMACS_UINT neql = 0; > + for (int i = 0; i < WORDS_PER_DOUBLE; i++) > + neql |= xu.word[i] ^ yu.word[i]; > + return !neql; > +} Wouldn't calling this upon every float comparison yield a non-negligible run-time penalty? Maybe we should use 'isnan' instead?