From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Andy Wingo Newsgroups: gmane.lisp.guile.user Subject: Re: Need help to understand a macro Date: Mon, 22 Mar 2010 21:16:34 +0100 Message-ID: References: <20100319085701.GA31143@raven.wolf.lan> <8E63698F-D6FF-4E42-8B6A-D2DE697C3E98@raeburn.org> <20100322192556.GB31143@raven.wolf.lan> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: dough.gmane.org 1269288973 13482 80.91.229.12 (22 Mar 2010 20:16:13 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Mon, 22 Mar 2010 20:16:13 +0000 (UTC) Cc: guile-user@gnu.org To: Josef Wolf Original-X-From: guile-user-bounces+guile-user=m.gmane.org@gnu.org Mon Mar 22 21:16:09 2010 Return-path: Envelope-to: guile-user@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 1Nto2h-0006C6-1K for guile-user@m.gmane.org; Mon, 22 Mar 2010 21:16:07 +0100 Original-Received: from localhost ([127.0.0.1]:37008 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nto2g-0007gw-Dh for guile-user@m.gmane.org; Mon, 22 Mar 2010 16:16:06 -0400 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nto2P-0007ah-HS for guile-user@gnu.org; Mon, 22 Mar 2010 16:15:49 -0400 Original-Received: from [140.186.70.92] (port=33381 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nto2O-0007Zp-6h for guile-user@gnu.org; Mon, 22 Mar 2010 16:15:49 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Nto2L-0005OU-8n for guile-user@gnu.org; Mon, 22 Mar 2010 16:15:48 -0400 Original-Received: from a-pb-sasl-quonix.pobox.com ([208.72.237.25]:62367 helo=sasl.smtp.pobox.com) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Nto2L-0005OQ-6j for guile-user@gnu.org; Mon, 22 Mar 2010 16:15:45 -0400 Original-Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by a-pb-sasl-quonix.pobox.com (Postfix) with ESMTP id 20F66A4C11; Mon, 22 Mar 2010 16:15:45 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=pG8OwLJDXvIIecri5++n/ktebG8=; b=m043ZJ 9n8jYjE4jM387vcJWJXVlKQZja05onG1ihOfagHnfgrESxCAPzMUiHbTt+GjKkLG 2D/6W9tNPfZpAyh+PCmcp1Fnr8CnmGFoOwIYWdba+MzqlFs6b1b4w6K3ef9St0Eg SWmVFIzxrF3R7zhaX9MXw2VSboqRW+0rfo5E4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=b4uQMFRp3HievYpKSdeZd+os4c24gvdp pXxugClkKeaEzHdufcepYXxPo/s0dY/DrjnyhnhfJDPaPfynUZuCUssIT1cP6XLy 19SmfkyX9ARguKfLN9i0Yas9CghpN0lWGSg4P9/gBUBNtcqH5M5lKafpKMTlMbIj NIM0Nup0lNM= Original-Received: from a-pb-sasl-quonix. (unknown [127.0.0.1]) by a-pb-sasl-quonix.pobox.com (Postfix) with ESMTP id 0E0C2A4C10; Mon, 22 Mar 2010 16:15:44 -0400 (EDT) Original-Received: from unquote (unknown [88.17.131.151]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by a-pb-sasl-quonix.pobox.com (Postfix) with ESMTPSA id 64B35A4C0C; Mon, 22 Mar 2010 16:15:42 -0400 (EDT) In-Reply-To: <20100322192556.GB31143@raven.wolf.lan> (Josef Wolf's message of "Mon, 22 Mar 2010 20:25:56 +0100") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.92 (gnu/linux) X-Pobox-Relay-ID: B1C442D2-35EF-11DF-97F4-D033EE7EF46B-02397024!a-pb-sasl-quonix.pobox.com X-detected-operating-system: by eggs.gnu.org: Solaris 10 (beta) X-BeenThere: guile-user@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: General Guile related discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: guile-user-bounces+guile-user=m.gmane.org@gnu.org Errors-To: guile-user-bounces+guile-user=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.user:7707 Archived-At: Hi Josef, I seem to be the negative guy in replies to you. Apologies for that! On Mon 22 Mar 2010 20:25, Josef Wolf writes: > On Fri, Mar 19, 2010 at 08:54:02AM -0400, Ken Raeburn wrote: >> >> The result of (if #f #f) is unspecified, not #f, according to r5rs. >> That means an implementation can produce whatever value it wants. In the R6RS, evaluating `(if #f #f)' returns "unspecified values" -- that is, even the number of values is unspecified. And in fact it would make sense for `(if #f #f)' to be the same as `(values)' -- an expression returning zero values. > I think I like this type of "unspecified". Much better than the > "undefined behavior" definition in C. Unfortunately it really is unspecified :) OK it's better than C, in the sense that it won't launch the missiles, but it would be better if evaluating: (+ 2 (if #f #f)) yielded an error of "too few values to continuation" rather than "don't know how to add #". Cheers, Andy -- http://wingolog.org/