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 11:19:06 -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> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1535470621 2150 195.159.176.226 (28 Aug 2018 15:37:01 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Aug 2018 15:37:01 +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 17:36:57 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 1fug37-0000Qb-Ei for guile-user@m.gmane.org; Tue, 28 Aug 2018 17:36:57 +0200 Original-Received: from localhost ([::1]:38744 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fug5D-0003Vp-Pf for guile-user@m.gmane.org; Tue, 28 Aug 2018 11:39:07 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:43945) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fug1H-0006xC-Pm for guile-user@gnu.org; Tue, 28 Aug 2018 11:35:04 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fufm3-00015g-5f for guile-user@gnu.org; Tue, 28 Aug 2018 11:19:20 -0400 Original-Received: from mail-wr1-x432.google.com ([2a00:1450:4864:20::432]:33634) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fufm2-00015M-Th for guile-user@gnu.org; Tue, 28 Aug 2018 11:19:19 -0400 Original-Received: by mail-wr1-x432.google.com with SMTP id v90-v6so1974359wrc.0 for ; Tue, 28 Aug 2018 08:19:18 -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=4AOTdnJCUu1lUdhW3zNaiShrOBxZ5bXHlmZU2wApTr8=; b=BxI0pIbvQmQ3/bZGmgkO5h3KLERRr6gJl2IIl65ZVYa2LurRGyza/RpShnnENf0SEe FZg8DnH6z90mz5xk5zudWcHFUeLrbxjrXiRq4UCCICSrQCAbhVlNk0PIOKUfv11Et6vM JfbVVF1DH/9i8Y1OFWjsTnZOJ4YKazY/2tLt3HqnjGpdt/JCgimbNkpEYirCuGk8GQQs OabpKxTQXY14pz2vt+hWlGwcL6xnxfDds4alVkQATlYICIY3n2BCanjxSnSEuO/UYBl4 hPKz12IW1ZM7wvNwBLKrQhpQrI61UbypItuEUROsIkBXOC20s/FkHa7e0dejURrG+RF8 2S0Q== 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=4AOTdnJCUu1lUdhW3zNaiShrOBxZ5bXHlmZU2wApTr8=; b=PLnwvPh43C4AY3P90by8c0YaACLwH0xRwGdqmuTF68m2C4kxzUlMkckhJF3xDlFISE c75bxtnOmF6ME750yNGW/0FEhqOYfAym7cd0hN5fijteaKhkUMd7pTJElISkrJz/pNx6 aO2bnTWBWn24GrCkDtURK33s1MheL4KB0c1PFD6ZqodjIBXE4sphFXNe72gl7xCBqCoX D9iEJSMJZ0pizjOvQzsqshfTZxNJhAJQ5bciCocW6INLJkYRheCjC3juQkvA0EI9UaTT d2FiiTPTlWR2aVBd9a6bpH9QEJGLWT4zEV96QSET1gO+Ehx6Pf2FdtWScW9QoR68uW7D T1cQ== X-Gm-Message-State: APzg51D21OSX2fgN8BLhdgSITiwqKfXvqVvtRx/3q46GA8bScAYhIbdZ a6a/tUvufeG2Blgw5NflhUxCFPqqkHYgFENO/kWinw== X-Google-Smtp-Source: ANB0VdbKgCLjMJ4MGb/LwRYBr5CEkazdwHVLJYleurAtNY59qOCZiy0LPW3/uNmMVVJWKYdwKmSjvDGBrvO/DavOlHk= X-Received: by 2002:adf:9142:: with SMTP id j60-v6mr1508306wrj.180.1535469557950; Tue, 28 Aug 2018 08:19:17 -0700 (PDT) In-Reply-To: <87va7vyo2q.fsf@netris.org> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:4864:20::432 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:14803 Archived-At: On Tue, Aug 28, 2018 at 3:01 AM Mark H Weaver wrote: > In RnRS, (define a (if #f #f)) is allowed and guaranteed to assign > *some* object to 'a' without signalling an error. Actually, the phrase used is "the result is unspecified", which unfortunately is not defined in any RnRS. Racket produces a syntax error in this situation at least in its default language. > However, it's not > specified what object will be assigned. It could be 2 or (foo bar) or > "the cow jumps over the moon". > In practice, it is #t, #f, (), or a unique unspecified object across all the Schemes I have tested, most often the last. -- John Cowan http://vrici.lojban.org/~cowan cowan@ccil.org LEAR: Dost thou call me fool, boy? FOOL: All thy other titles thou hast given away: That thou wast born with.