From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: Using the GNU GMP Library for Bignums in Emacs Date: Sun, 22 Apr 2018 21:41:02 -0700 Organization: UCLA Computer Science Department Message-ID: References: <29f933ac-a6bf-8742-66a7-0a9d6d3e5a88@disroot.org> <83bmecy6fx.fsf@gnu.org> <0d3175d8-d996-651e-b221-71978bde3a65@cs.ucla.edu> <42cbc5ab-2f02-4aa5-4b19-7b2357f91692@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1524458350 25138 195.159.176.226 (23 Apr 2018 04:39:10 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 23 Apr 2018 04:39:10 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 Cc: eller.helmut@gmail.com, emacs-devel@gnu.org To: rms@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Apr 23 06:39:06 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 1fATFo-0006Qq-M2 for ged-emacs-devel@m.gmane.org; Mon, 23 Apr 2018 06:39:04 +0200 Original-Received: from localhost ([::1]:38315 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fATHv-0001f1-8w for ged-emacs-devel@m.gmane.org; Mon, 23 Apr 2018 00:41:15 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:38197) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fATHo-0001eT-Ea for emacs-devel@gnu.org; Mon, 23 Apr 2018 00:41:09 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fATHl-0004VS-5i for emacs-devel@gnu.org; Mon, 23 Apr 2018 00:41:08 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:44408) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fATHk-0004Uv-W8; Mon, 23 Apr 2018 00:41:05 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id B12DF1616DE; Sun, 22 Apr 2018 21:41:03 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id OsWX3JBG6DZw; Sun, 22 Apr 2018 21:41:02 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id E679D1616E0; Sun, 22 Apr 2018 21:41:02 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id b4yRMBqtaTNn; Sun, 22 Apr 2018 21:41:02 -0700 (PDT) Original-Received: from [192.168.1.9] (unknown [47.154.30.119]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id C18FC1616DE; Sun, 22 Apr 2018 21:41:02 -0700 (PDT) In-Reply-To: Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 131.179.128.68 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:224799 Archived-At: Richard Stallman wrote: > > The usual approach for this is to format negative numbers with a l= eading minus > > sign, so that (format "%x" -1) returns "-1". This is what Emac Lis= p should have >=20 > I think that change is likely to break things. If you WANT a hex > string, you probably want it to be all hex, regardless of value. No doubt people occasionally want C-like formatting (i.e., print a negati= ve=20 number modulo 2**W where W is the word width), but once we have bignums t= he=20 notion of the "word width" becomes dubious, and in practice it's cleaner = and=20 more useful to print hexadecimal integers in the usual mathematical way. = That's=20 the tradition in Common Lisp, in Python, and in every other language I kn= ow that=20 has bignums and has the %x format or something similar. > I would expect that each use of %x probably has a certain number of bit= s > in mind. Perhaps %x should take a number of bits and output modularly. > So %24x would output 24 bits' worth. We could invent a special syntax along those lines, though it would need = to=20 differ from "%24x" which already means pad with spaces to 24 characters.=20 However, there's little point to a special syntax since one can easily ac= hieve=20 the same effect without it. For example, to format the low-order 24 bits = of N,=20 one can already use (format "%x" (logand N #xffffff)) and this will conti= nue to=20 work even if bignums are introduced.