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: Will guile support R7RS terminating "equal?" in the presence of cycle? Date: Sat, 01 Sep 2012 15:30:26 +0200 Message-ID: <87wr0dq39p.fsf@gnu.org> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: ger.gmane.org 1346506258 11100 80.91.229.3 (1 Sep 2012 13:30:58 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 1 Sep 2012 13:30:58 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Sat Sep 01 15:30:57 2012 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1T7nmm-0002D8-Sc for guile-devel@m.gmane.org; Sat, 01 Sep 2012 15:30:53 +0200 Original-Received: from localhost ([::1]:51952 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T7nmk-0005wF-D5 for guile-devel@m.gmane.org; Sat, 01 Sep 2012 09:30:50 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:37994) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T7nmh-0005w8-8R for guile-devel@gnu.org; Sat, 01 Sep 2012 09:30:48 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T7nmg-0003Uo-2L for guile-devel@gnu.org; Sat, 01 Sep 2012 09:30:47 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:38884) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T7nmf-0003Ui-Nn for guile-devel@gnu.org; Sat, 01 Sep 2012 09:30:45 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1T7nmd-0001xG-Mk for guile-devel@gnu.org; Sat, 01 Sep 2012 15:30:43 +0200 Original-Received: from reverse-83.fdn.fr ([80.67.176.83]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 01 Sep 2012 15:30:43 +0200 Original-Received: from ludo by reverse-83.fdn.fr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 01 Sep 2012 15:30:43 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 19 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: reverse-83.fdn.fr X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 16 Fructidor an 220 de la =?iso-8859-1?Q?R=E9volutio?= =?iso-8859-1?Q?n?= 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/5.130005 (Ma Gnus v0.5) Emacs/24.2 (gnu/linux) Cancel-Lock: sha1:ey5MH6bVC2OQCiepqh1/eANgsWo= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: guile-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:14836 Archived-At: Hi, "David A. Wheeler" skribis: > *However*, the current R7RS draft for "equal?" requires termination > even in the presence of cycles, as well as impose other requirements > on "write" and "display" in the presence of cycles. Will guile > support such changes? I worry that these new requirements on "equal?" > will have such a high overhead that people won't do it. But perhaps > those fear are misplaced. Are you talking about termination in the case of circular lists, or for arbitrary data structures? The former is easy and reasonably cheap, but the latter may require more work, indeed. Thanks, Ludo’.