From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Mark H Weaver Newsgroups: gmane.lisp.guile.user Subject: Re: A value for "nothing" Date: Mon, 27 Aug 2018 15:49:42 -0400 Message-ID: <874lfftwrt.fsf@netris.org> References: <21036238.c6yQEfjfIL@aleksandar-ixtreme-m5740> <3467110.H24gZIzStD@aleksandar-ixtreme-m5740> <87ftz0vidc.fsf@netris.org> <15511073.3h7x93ioX3@aleksandar-ixtreme-m5740> <87lg8s9e9b.fsf@gnu.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 1535399435 12635 195.159.176.226 (27 Aug 2018 19:50:35 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 27 Aug 2018 19:50:35 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) Cc: guile-user@gnu.org To: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=) Original-X-From: guile-user-bounces+guile-user=m.gmane.org@gnu.org Mon Aug 27 21:50:31 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 1fuNWx-0003BY-3g for guile-user@m.gmane.org; Mon, 27 Aug 2018 21:50:31 +0200 Original-Received: from localhost ([::1]:34894 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuNZ3-0004V7-FB for guile-user@m.gmane.org; Mon, 27 Aug 2018 15:52:41 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:46545) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuNXp-00045G-4V for guile-user@gnu.org; Mon, 27 Aug 2018 15:51:25 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fuNXl-0001cp-JA for guile-user@gnu.org; Mon, 27 Aug 2018 15:51:25 -0400 Original-Received: from world.peace.net ([64.112.178.59]:47814) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fuNXi-0001Zf-Ps; Mon, 27 Aug 2018 15:51:20 -0400 Original-Received: from mhw by world.peace.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1fuNXf-0005ez-Nm; Mon, 27 Aug 2018 15:51:15 -0400 In-Reply-To: <87lg8s9e9b.fsf@gnu.org> ("Ludovic \=\?utf-8\?Q\?Court\=C3\=A8s\=22'\?\= \=\?utf-8\?Q\?s\?\= message of "Mon, 27 Aug 2018 14:37:36 +0200") X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 64.112.178.59 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:14788 Archived-At: ludo@gnu.org (Ludovic Court=C3=A8s) writes: > I would suggesting returning zero values, using: > > (values) > > That way, if a caller wrongfully attempts to get at the return value of > that procedure, it=E2=80=99ll get an error. > > Fibers does that in several places, and I think it=E2=80=99s a good conve= ntion > as it conveys exactly what you want. You cannot store (values) in a variable or data structure, so it wouldn't work here. The issue under discussion is how to represent MessagePack's "nil", which is one of the possible values that a MessagePack can have, alongside booleans, integers, floats, strings, arrays, etc. MessagePack is similar to JSON, so the question we're discussing is analogous to the question of how to represent JSON's "null" in Scheme. Mark