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: Making 'eq' == 'eql' in bignum branch Date: Sun, 29 Jul 2018 17:35:18 +0300 Message-ID: <83600yt8ih.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> <76081b5d-8c10-0a37-2c97-d4864c0faa80@cs.ucla.edu> <09153aed-361d-4f82-d9ac-b502314769ae@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1532874805 7363 195.159.176.226 (29 Jul 2018 14:33:25 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 29 Jul 2018 14:33:25 +0000 (UTC) Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Jul 29 16:33:21 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 1fjml6-0001on-T6 for ged-emacs-devel@m.gmane.org; Sun, 29 Jul 2018 16:33:21 +0200 Original-Received: from localhost ([::1]:48626 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fjmnD-0005gp-EX for ged-emacs-devel@m.gmane.org; Sun, 29 Jul 2018 10:35:31 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39132) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fjmn0-0005gX-UF for emacs-devel@gnu.org; Sun, 29 Jul 2018 10:35:19 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fjmmw-0004Ax-S1 for emacs-devel@gnu.org; Sun, 29 Jul 2018 10:35:18 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:40655) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fjmmw-0004An-KT; Sun, 29 Jul 2018 10:35:14 -0400 Original-Received: from [176.228.60.248] (port=1190 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1fjmmw-0004gC-1v; Sun, 29 Jul 2018 10:35:14 -0400 In-reply-to: <09153aed-361d-4f82-d9ac-b502314769ae@cs.ucla.edu> (message from Paul Eggert on Sat, 28 Jul 2018 20:34:32 -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:227946 Archived-At: > From: Paul Eggert > Date: Sat, 28 Jul 2018 20:34:32 -0700 > > How about if we do to floats what fixnum+bignum would do to integers? > > That is, on a 64-bit host, if the low-order 4 bits of the significand are all > zero, we encode the floating-point number directly in the Lisp_Object (with a > tag) so that the Lisp_Object need not be dereferenced and uses zero bytes of > floating-point heap. Otherwise, we put the floating-point value into a special > hash-consed table that should use about 16 bytes per entry (one for the double, > one for the pointer to it). How likely is it to see a floating-point number with 4 low-order bits of mantissa zero?