From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: John Cowan Newsgroups: gmane.lisp.guile.user Subject: Re: A value for "nothing" Date: Tue, 28 Aug 2018 12:12:34 -0400 Message-ID: References: <21036238.c6yQEfjfIL@aleksandar-ixtreme-m5740> <87sh30vqmm.fsf@netris.org> <20180827080415.GB10407@tuxteam.de> <87wosbsh5m.fsf@netris.org> <87sh2zsfle.fsf@netris.org> <31c7a870-aaf2-3f0e-2ef4-be4dc783a842@gmail.com> <87va7vyo2q.fsf@netris.org> <87h8jeijr2.fsf@netris.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1535472952 31529 195.159.176.226 (28 Aug 2018 16:15:52 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Aug 2018 16:15:52 +0000 (UTC) Cc: guile-user@gnu.org, Matt Wette To: Mark H Weaver Original-X-From: guile-user-bounces+guile-user=m.gmane.org@gnu.org Tue Aug 28 18:15:48 2018 Return-path: Envelope-to: guile-user@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 1fugeg-00084p-GU for guile-user@m.gmane.org; Tue, 28 Aug 2018 18:15:46 +0200 Original-Received: from localhost ([::1]:38966 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuggm-0001Iq-PN for guile-user@m.gmane.org; Tue, 28 Aug 2018 12:17:56 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:35891) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fugg1-0001Ea-Mu for guile-user@gnu.org; Tue, 28 Aug 2018 12:17:10 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fugbn-0001ih-7l for guile-user@gnu.org; Tue, 28 Aug 2018 12:12:48 -0400 Original-Received: from mail-wm0-x229.google.com ([2a00:1450:400c:c09::229]:32822) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fugbm-0001hv-R7 for guile-user@gnu.org; Tue, 28 Aug 2018 12:12:47 -0400 Original-Received: by mail-wm0-x229.google.com with SMTP id i134-v6so2287947wmf.0 for ; Tue, 28 Aug 2018 09:12:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ccil-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CHDgGU9C917VPUCYxTjtAhETyeBUyUgacEHRTa+SLd4=; b=WjTZVZDggcoAXESuUH0nH7W2TP3S0Muu9X2/X/aPTMziIFK/LPJeB5C9r5ezyT36g8 mi+9PFdqlth3sVZNecisgW4CuHrsPndVOacS2Aoqplda6dP8gOO6Z0m7lrA1oz1qMxt8 jfJPXktTT9EZYSXe+r2SV9ou2bSQXo8epci95r+mTYPbK9yNjhrFzaNxSpMjuRi5kUO1 rulfcX7LUZVaiUAqp51MXln1VtzOCzcS1bhj6/B5ofr9evuMQ8eNbki3wamsGNA+bXgK 8pVsNSvmZQBNgRTSEI2aK77JuDOCgymhbLzr/1xI7sAmLR8Vg3kZR0HlGa0tYw4H0D/Z IaGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CHDgGU9C917VPUCYxTjtAhETyeBUyUgacEHRTa+SLd4=; b=GR0ppHjPd6L8gYZr090uUWk0+AQ6ifMp5GfO2ube44y0gJdUBtBSObSF8N0caUjv1a 82qqoQJA9npoPr1vZOg0i6FKBJrBcW6lE4v55a1HQvpO5nS185HckIJHOheI1bBK3Miy oJk9Z6ATsLCfKXHMSmacnMb65w1hja7KqQOjp7C5fSbOkZr4LpRgQnYCr8uj2qTqFT7V NRFInqCU0TXE2nR79SrwqzlQEUBi9m0KkliZx+5zziy5rNWeMIRZdvl2M9Jdr2j2HCpG eJeSbbAqWshISAiJeEqSjXLV32KNSqZ+D93p7LVxd8F8MCLJIeyUEwyQOpbjszYBJk57 IrpQ== X-Gm-Message-State: APzg51CvoS/2ThbdmNugZt4qxVo3T67H7iWOcCaPSflyFGm+h/W5ssUQ nxHln8jbPe9Ckk3Q668vIixHZQJbNEgLI1A5mIL9/A== X-Google-Smtp-Source: ANB0VdYgrfijkwm3+7NTKLVGu7hufvs3eE71/3/oo1V0UDC8Qrqk8aF5LM5OykfSdDvAi2Q+JtLG5/7roTWSSoIgIV8= X-Received: by 2002:a1c:700a:: with SMTP id l10-v6mr1854877wmc.90.1535472765603; Tue, 28 Aug 2018 09:12:45 -0700 (PDT) In-Reply-To: <87h8jeijr2.fsf@netris.org> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:400c:c09::229 X-Content-Filtered-By: Mailman/MimeDel 2.1.21 X-BeenThere: guile-user@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: General Guile related discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-user-bounces+guile-user=m.gmane.org@gnu.org Original-Sender: "guile-user" Xref: news.gmane.org gmane.lisp.guile.user:14806 Archived-At: On Tue, Aug 28, 2018 at 11:40 AM Mark H Weaver wrote: > That's the phrase used in R7RS-small, which fails to define it, as you > noted, but that shortcoming is limited to R7RS. > The relevant sentences in R5RS and R7RS are identical: " If yields a false value and no is specified, then the result of the expression is unspecified." Likewise, the paragraph from 1.3.2 you quote below is identical in both standards. So either they both define it or they both don't. In R6RS, section 11.4.3 (Conditionals) provides this example: > Unlike Wil Clinger, and apparently you, I don't believe that examples in specs are normative. But setting that aside for the moment: > I take the use of the singular form of "value" here to imply that it > returns only one value. > In R6RS 11.13, vector-set! is said to return unspecified values (note plural), but in the examples appears "=E2=87=92 unspecified", showing that = this notation can be used where multiple unspecified values (or zero values) are allowed. In practice, I know of no Scheme implementation that returns other than one value in any of these "unspecified values" situations, which IMO is a Good Thing. --=20 John Cowan http://vrici.lojban.org/~cowan cowan@ccil.org With techies, I've generally found If your arguments lose the first round Make it rhyme, make it scan / Then you generally can Make the same stupid point seem profound! --Jonathan Robie