From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: ludo@gnu.org (Ludovic =?iso-8859-1?Q?Court=E8s?=) Newsgroups: gmane.lisp.guile.devel Subject: Re: fix for expt bug Date: Thu, 04 Nov 2010 00:27:25 +0100 Message-ID: <87bp66rns2.fsf@gnu.org> References: <8762whnc4d.fsf@yeeloong.netris.org> <87r5f4l3yt.fsf@yeeloong.netris.org> <87aalrxim7.fsf@yeeloong.netris.org> <87wrouwf6b.fsf@yeeloong.netris.org> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: dough.gmane.org 1288835963 2377 80.91.229.12 (4 Nov 2010 01:59:23 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Thu, 4 Nov 2010 01:59:23 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Thu Nov 04 02:59:16 2010 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1PDp6h-0003GC-QD for guile-devel@m.gmane.org; Thu, 04 Nov 2010 02:59:16 +0100 Original-Received: from localhost ([127.0.0.1]:48238 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PDp6h-000527-7y for guile-devel@m.gmane.org; Wed, 03 Nov 2010 21:59:15 -0400 Original-Received: from [140.186.70.92] (port=53406 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PDonD-0002Fq-HT for guile-devel@gnu.org; Wed, 03 Nov 2010 21:39:12 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PDmkK-0002pv-Gc for guile-devel@gnu.org; Wed, 03 Nov 2010 19:28:01 -0400 Original-Received: from lo.gmane.org ([80.91.229.12]:50238) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PDmkK-0002ph-3h for guile-devel@gnu.org; Wed, 03 Nov 2010 19:28:00 -0400 Original-Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1PDmk7-0005cA-M1 for guile-devel@gnu.org; Thu, 04 Nov 2010 00:27:47 +0100 Original-Received: from yoda.fdn.fr ([80.67.169.18]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 04 Nov 2010 00:27:47 +0100 Original-Received: from ludo by yoda.fdn.fr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 04 Nov 2010 00:27:47 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 40 Original-X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: yoda.fdn.fr X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 14 Brumaire an 219 de la =?iso-8859-1?Q?R=E9volution?= X-PGP-Key-ID: 0xEA52ECF4 X-PGP-Key: http://www.fdn.fr/~lcourtes/ludovic.asc X-PGP-Fingerprint: 83C4 F8E5 10A3 3B4C 5BEA D15D 77DD 95E2 EA52 ECF4 X-OS: x86_64-unknown-linux-gnu User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) Cancel-Lock: sha1:MmBqcyLJs02Bm4F5K60wyBO0ywY= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-BeenThere: guile-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:11115 Archived-At: Hi Mark, Mark H Weaver writes: > I just realized that there is a better way to fix these bugs. We don't > need a new top-level case in expt after all. Instead, we generalize the > scm_integer_expt case to support inexact integer exponents. You mean “inexact number”, right? The doc for ‘integer-expt’ makes the same mistake: "Return @var{n} raised to the power @var{k}. @var{k} must be an\n" "exact integer, @var{n} can be any number.\n" However, an integer is necessarily an exact number, whereas the converse isn’t true: --8<---------------cut here---------------start------------->8--- scheme@(guile-user) [25]> (exact? 2/3) $4 = #t scheme@(guile-user) [25]> (integer? 2/3) $5 = #f --8<---------------cut here---------------end--------------->8--- In actuality, ‘integer-expt’ expects K to be an integer (fixnum or bignum). So I suspect that your patch doesn’t work because ‘inexact->exact’ returns something that’s obviously not necessarily an integer: --8<---------------cut here---------------start------------->8--- scheme@(guile-user) [25]> (inexact->exact 2.3) $6 = 2589569785738035/1125899906842624 --8<---------------cut here---------------end--------------->8--- Does that make sense? Thanks, Ludo’.