From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Helmut Eller Newsgroups: gmane.emacs.devel Subject: Re: Using the GNU GMP Library for Bignums in Emacs Date: Tue, 24 Apr 2018 07:45:30 +0200 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> <1f58acbf-a7d8-bf4e-3d0e-a285515a22e6@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1524548624 31277 195.159.176.226 (24 Apr 2018 05:43:44 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 24 Apr 2018 05:43:44 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) Cc: Paul Eggert , Richard Stallman To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Apr 24 07:43:40 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 1fAqjr-00081L-KG for ged-emacs-devel@m.gmane.org; Tue, 24 Apr 2018 07:43:39 +0200 Original-Received: from localhost ([::1]:56664 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fAqly-0001tG-Fl for ged-emacs-devel@m.gmane.org; Tue, 24 Apr 2018 01:45:50 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:58839) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fAqlr-0001ss-IK for emacs-devel@gnu.org; Tue, 24 Apr 2018 01:45:44 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fAqlo-0002bh-Vq for emacs-devel@gnu.org; Tue, 24 Apr 2018 01:45:43 -0400 Original-Received: from [195.159.176.226] (port=44615 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fAqlo-0002av-OE for emacs-devel@gnu.org; Tue, 24 Apr 2018 01:45:40 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1fAqjf-0007oV-8C for emacs-devel@gnu.org; Tue, 24 Apr 2018 07:43:27 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 22 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:7PYM1VdQmNH7UiRq2YYiGErG6sA= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] 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:224826 Archived-At: On Mon, Apr 23 2018, Paul Eggert wrote: > Even in the standard C library (which lacks bignums), the %x printf > format is supposed to be used only with unsigned integers. Nowadays > GCC even optionally warns about using %x on signed integers. Maybe %x should then print the (shortest) two's complement representation for bignums. In Common Lisp: (defun 2comp (x) (format nil "~x" (logand x (1- (ash 1 (+ 1 (integer-length x))))))) (2comp -1) => "1" (2comp -2) => "2" (2comp -3) => "5" (2comp -15) => "11" (2comp -16) => "10" In practice, only integers smaller than most-negative-fixnum would use this rule. Helmut