From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: David Kastrup Newsgroups: gmane.lisp.guile.bugs Subject: bug#17474: Making *unspecified* equivalent to (values) would seem convenient Date: Mon, 12 May 2014 18:58:25 +0200 Message-ID: <87iopbue6m.fsf@fencepost.gnu.org> References: <87r43zuswp.fsf@fencepost.gnu.org> <8738gfyoxm.fsf@gnu.org> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1399914257 12608 80.91.229.3 (12 May 2014 17:04:17 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 12 May 2014 17:04:17 +0000 (UTC) Cc: 17474@debbugs.gnu.org To: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=) Original-X-From: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Mon May 12 19:04:09 2014 Return-path: Envelope-to: guile-bugs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Wjte4-0000Q6-Cb for guile-bugs@m.gmane.org; Mon, 12 May 2014 19:04:08 +0200 Original-Received: from localhost ([::1]:38909 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjte3-0007gt-Po for guile-bugs@m.gmane.org; Mon, 12 May 2014 13:04:07 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:59890) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjtdz-0007dL-SD for bug-guile@gnu.org; Mon, 12 May 2014 13:04:04 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wjtdy-0006Zw-SV for bug-guile@gnu.org; Mon, 12 May 2014 13:04:03 -0400 Original-Received: from debbugs.gnu.org ([140.186.70.43]:43563) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjtdy-0006Zd-Q4 for bug-guile@gnu.org; Mon, 12 May 2014 13:04:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.80) (envelope-from ) id 1Wjtdy-0002JN-A3 for bug-guile@gnu.org; Mon, 12 May 2014 13:04:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: David Kastrup Original-Sender: "Debbugs-submit" Resent-CC: bug-guile@gnu.org Resent-Date: Mon, 12 May 2014 17:04:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 17474 X-GNU-PR-Package: guile X-GNU-PR-Keywords: Original-Received: via spool by 17474-submit@debbugs.gnu.org id=B17474.13999141848781 (code B ref 17474); Mon, 12 May 2014 17:04:02 +0000 Original-Received: (at 17474) by debbugs.gnu.org; 12 May 2014 17:03:04 +0000 Original-Received: from localhost ([127.0.0.1]:60912 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1Wjtd1-0002HX-RN for submit@debbugs.gnu.org; Mon, 12 May 2014 13:03:04 -0400 Original-Received: from fencepost.gnu.org ([208.118.235.10]:43626 ident=Debian-exim) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1Wjtcz-0002H8-Ro for 17474@debbugs.gnu.org; Mon, 12 May 2014 13:03:02 -0400 Original-Received: from localhost ([127.0.0.1]:50931 helo=lola) by fencepost.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wjtcz-0008FE-4h; Mon, 12 May 2014 13:03:01 -0400 Original-Received: by lola (Postfix, from userid 1000) id B0D12E0F55; Mon, 12 May 2014 19:03:00 +0200 (CEST) In-Reply-To: <8738gfyoxm.fsf@gnu.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 140.186.70.43 X-BeenThere: bug-guile@gnu.org List-Id: "Bug reports for GUILE, GNU's Ubiquitous Extension Language" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Original-Sender: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.bugs:7455 Archived-At: ludo@gnu.org (Ludovic Court=C3=A8s) writes: > R5RS defines =E2=80=98values=E2=80=99 as: > > (define (values . things) > (call-with-current-continuation > (lambda (cont) (apply cont things)))) > > Thus, a conforming implementation must raise a run-time error when the > continuation of a (values) form expects one or more values. No. From R5RS: -- procedure: call-with-current-continuation proc [...] The escape procedure accepts the same number of arguments as the continuation to the original call to call-with-current-continuation. Except for continuations created by the `call-with-values' procedure, all continuations take exactly one value. The effect of passing no value or more than one value to continuations that were not created by call-with-values is unspecified. Please reread the last sentence. "unspecified". In fact, passing more than one value to continuations that were not created by call-with-values already does not raise a runtime error but instead just drops the additional values: (+ (values 4 5) 5) =3D> 9 This patch _provides_ a default value when 0 values are given. That's filling in a different unspecified behavior than throwing an error, but Guile already fills in a different unspecified behavior than throwing an error for multiple values. So this behavior is neither out of line, nor against the standard. It is merely a more convenient behavior for a situation that the standard left unspecified. --=20 David Kastrup