<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=utf-8"> <META content="MSHTML 6.00.2900.2963" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV style="FONT: 10pt arial"><FONT face="Courier New">Hi Robby and Matthias,</FONT></DIV> <DIV style="FONT: 10pt arial"><FONT face="Courier New">Agreed. I was a little bit hasty in my reaction, sorry. An implementation necessarily is an instantiation, like an element of a set. We all known what happens if the border between elements and sets are confused. Personally I think that an implementation should follow the law as far as possible and desirable, but where law is not clear or contrary to common sense, the implementator has the freedom to make things clear. Just mho. Personally I don't think that R5RS specifies whether or not 'unspecified' is uniquely specified or unspecified. I noticed that the same kind of problems is discussed on the R6RS list. </FONT><FONT face="Courier New">Best wishes, Jos</FONT></DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=robby@cs.uchicago.edu href="mailto:robby@cs.uchicago.edu">Robby Findler</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=jos.koot@telefonica.net href="mailto:jos.koot@telefonica.net">Jos Koot</A> </DIV> <DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=plt-scheme@list.cs.brown.edu href="mailto:plt-scheme@list.cs.brown.edu">plt-scheme@list.cs.brown.edu</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, November 14, 2006 1:28 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [plt-scheme] Please help test version 359.100</DIV> <DIV><BR></DIV> <DIV>On Nov 14, 2006, at 6:36 AM, Jos Koot wrote:<BR><BR>> ----- Original Message -----<BR>> From: Matthias Felleisen<BR>> To: Jacob Matthews<BR>> Cc: Robby Findler ; <A href="mailto:plt-scheme@list.cs.brown.edu">plt-scheme@list.cs.brown.edu</A><BR>> Sent: Tuesday, November 14, 2006 3:39 AM<BR>> Subject: Re: [plt-scheme] Please help test version 359.100<BR>><BR>> I don't think this is relevant. The true question is whether<BR>><BR>>   (+ (for-each add1 '()) (for-each sub1 '()))<BR>><BR>> steps to<BR>><BR>>   (+ some-value some-value)<BR>><BR>> or to<BR>><BR>>   (+ some-value some-different-value)<BR>><BR>> I believe that the second one is the case already. -- Matthias<BR>><BR>>  Then why do I get: (eq? (for-each add1 '()) (for-each sub1 '())) -- <BR>> > #t ?<BR>> (version 359.100-svn4nov2006) Greetings, Jos Koot<BR><BR><BR>Because an implementation can satisfy a specification without being  <BR>equivalent to it. I conjecture that no Scheme implementation is  <BR>equivalent to R5RS's specification.<BR><BR>In other words, test a lot on many different implementations and you  <BR>still won't know for sure what the legal language means. -- Matthias<BR></DIV> <DIV><FONT face="Courier New" size=2></FONT> </DIV> <DIV>At Tue, 14 Nov 2006 12:54:54 +0100, "Jos Koot" wrote:<BR>> ----- Original Message ----- <BR>>   From: Robby Findler <BR>>   To: Matthias Felleisen <BR>>   Cc: Jacob Matthews ; <A href="mailto:plt-scheme@list.cs.brown.edu">plt-scheme@list.cs.brown.edu</A> <BR>>   Sent: Tuesday, November 14, 2006 4:09 AM<BR>>   Subject: Re: [plt-scheme] Please help test version 359.100<BR>> <BR>> <BR>>   My reading indicates they would both be legal.<BR>> <BR>>   What seems to be illegal is<BR>> <BR>>     (for-each (lambda (x) (values x x)) (list 1))<BR>>     --><BR>>     (values 1 1)<BR>><BR>> If I understand well, the procedure is invoked in tail position when<BR>> reaching the last element of the list. To me it seems up to the<BR>> continuation of the for-each call how many values can be returned. (I<BR>> don't bother much about this for in my code for-each calls always (I<BR>> hope) have continuations that disregard any returned value(s))<BR><BR>That's what for-each does (did, until very recently anyways). The<BR>question is whether or not that's legal.<BR><BR>Robby</DIV></BLOCKQUOTE></BODY></HTML>