From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Matt Wette Newsgroups: gmane.lisp.guile.user Subject: Re: A value for "nothing" Date: Mon, 27 Aug 2018 17:50:14 -0700 Message-ID: <31c7a870-aaf2-3f0e-2ef4-be4dc783a842@gmail.com> References: <21036238.c6yQEfjfIL@aleksandar-ixtreme-m5740> <87sh30vqmm.fsf@netris.org> <20180827080415.GB10407@tuxteam.de> <87wosbsh5m.fsf@netris.org> <87sh2zsfle.fsf@netris.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1535417346 27686 195.159.176.226 (28 Aug 2018 00:49:06 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Aug 2018 00:49:06 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 To: guile-user@gnu.org Original-X-From: guile-user-bounces+guile-user=m.gmane.org@gnu.org Tue Aug 28 02:49:02 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 1fuSBq-00075r-7G for guile-user@m.gmane.org; Tue, 28 Aug 2018 02:49:02 +0200 Original-Received: from localhost ([::1]:35685 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuSDw-0008Ml-LD for guile-user@m.gmane.org; Mon, 27 Aug 2018 20:51:12 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:36637) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuSD6-000834-7l for guile-user@gnu.org; Mon, 27 Aug 2018 20:50:21 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fuSD3-0007Wq-NA for guile-user@gnu.org; Mon, 27 Aug 2018 20:50:20 -0400 Original-Received: from mail-pg1-x532.google.com ([2607:f8b0:4864:20::532]:35510) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fuSD3-0007W8-Cd for guile-user@gnu.org; Mon, 27 Aug 2018 20:50:17 -0400 Original-Received: by mail-pg1-x532.google.com with SMTP id z4-v6so378306pgv.2 for ; Mon, 27 Aug 2018 17:50:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-transfer-encoding:content-language; bh=NrSsZ2LOpCPlQsRA+Qoi8s7EfssINzGI9bTlD74oCbg=; b=vZVNmLXRPxjjlj8DJOPUIlPDg4PL3QBKpZBs2dPfVGb68RhU4AKm5XImd3q20UUMwd MH/mag9El0QiZKHs07t03JWWUTyaTJ5aR1QOPre1GiFWyl3rHhBsIV/gemRjTwdXpryr xa3CSy7CzTQDY9UsSraqTfwrw4TLddt0Nqvl7IY79usCP027QOZlM4BUB9s0ecG0MFQ/ sBf9GThzIhxqbSYwGhlWo5MeHDZD3qhNR46AI1tqFsVJZxTBZiYEv8KeGrRefwAUv782 YcE8yGqG6SjD7i+96Ul9y2zCZk2m1CuBko/qATkW0pfH0M0sage6rF6Eu4eMzIpH0qPD 2hLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=NrSsZ2LOpCPlQsRA+Qoi8s7EfssINzGI9bTlD74oCbg=; b=Ce4spcYHhZ8slqJmyShpocBcIX3EmlyB+9klqvjw3wot5KwkrZJ1Uuye8ymBp4A1T8 vHefiTyelFsumYBMoBAJxZQUs5Bfl8XLULEZWiOo8/7lu+06o+AIheWnzCu8aY3zkwWP GtsgSi70qSdRUBH+0V+8AiXHERQ2IG8biuX0ieZqysGHNlPyg2NfGGl38vCoxxb1IdYy Jhiw88wwwfZkq6+Iz+q0BpXkQ2GGfJcgwnx3prHJo3EFkEUllOp8vRSpZ5t7eNNoZn/E ioeeztPCjLuZbroMkgNb4L3qbo77Y/RRPNvsy0FznIAsAOLO5xYkyhM+hEO9T/5WMTed NOfA== X-Gm-Message-State: APzg51DtYcVphC8W9KI77TTRC+Xcoa5GDtidcmrCgLSm+SSehtemO76N A2sXBszYlTryv4Pi59CSGlb/VWIm X-Google-Smtp-Source: ANB0VdZZGD+ahbHFAuU2yjoUQ/4H5YtACWz6hU5L44ppmFDWIm58hrhrTHh63/qg/tXfEKrTkWD2iQ== X-Received: by 2002:a65:5545:: with SMTP id t5-v6mr14089560pgr.157.1535417416060; Mon, 27 Aug 2018 17:50:16 -0700 (PDT) Original-Received: from [192.168.2.183] (216-165-229-229.championbroadband.com. [216.165.229.229]) by smtp.gmail.com with ESMTPSA id v22-v6sm697119pfi.60.2018.08.27.17.50.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Aug 2018 17:50:15 -0700 (PDT) In-Reply-To: <87sh2zsfle.fsf@netris.org> Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::532 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:14799 Archived-At: Is it reasonable to expect that if a value can be assigned to a variable then a predicate exists to test for that value type? So, if (define a (if #f #f)) does not signal an error then there should be a predicate to indicate the value associated with a is unspecified? If the define allowed in RnRS? I don't believe there is a predicate to test for this. (I could be wrong.) Comments? Matt