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<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE
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<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=matthias@ccs.neu.edu
href="mailto:matthias@ccs.neu.edu">Matthias Felleisen</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=jacobm@cs.uchicago.edu
href="mailto:jacobm@cs.uchicago.edu">Jacob Matthews</A> ; <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 4:09
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [plt-scheme] Please help
test version 359.100</DIV>
<DIV><BR></DIV>
<DIV>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)</DIV></BLOCKQUOTE>
<DIV><FONT face="Courier New" size=2>If I understand well, the procedure is
invoked in tail position when reaching the last element of the list. To me it
seems up to the continuation of the for-each call how many values can be
returned. (I don't bother much about this for in my code for-each calls
always (I hope) have continuations that disregard any returned
value(s)) </FONT></DIV><FONT face="Courier New" size=2></FONT>
<DIV><FONT face="Courier New"><FONT size=2><FONT face="Courier New"
size=2></FONT></FONT></FONT> </DIV>
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<DIV><FONT face="Courier New" size=2></FONT> </DIV>
<DIV><BR><BR>Robby<BR><BR>At Mon, 13 Nov 2006 21:39:11 -0500, Matthias
Felleisen wrote:<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>> <BR>> On Nov 13, 2006, at 6:52
PM, Jacob Matthews wrote:<BR>> <BR>> > On Nov 13, 2006, at 5:31 PM,
Robby Findler wrote:<BR>> ><BR>> >> Is "some object" allowed to
be multiple values or not? That text<BR>> >> suggests not.<BR>>
><BR>> > "Types are associated with values (also called objects)
rather than <BR>> > with variables" (section 1.1) seems to be the
only definition of <BR>> > what an 'object' is. I think it's clear
that they are saying that <BR>> > values are also called objects,
and that by the normal rules of <BR>> > English we can conclude
that the singular 'object' means the same <BR>> > thing as the
singular 'value'. So the question becomes, are <BR>> > multiple
values the same thing as a single value? The report seems <BR>>
> to think not (I'm going here by the descriptions of the values and
<BR>> > call-with-values functions in section 6.4), though it plays
its <BR>> > usual trick of simply not defining what happens if a
context <BR>> > expects a single value and it receives multiple
ones.<BR>> ><BR>> > Applying this back to the original question, I
think we have to <BR>> > conclude that for-each is supposed to be
able to be called in <BR>> > contexts that expect exactly one
value. In Schemes like PLT Scheme <BR>> > where contexts that
expect one value signal an error if they <BR>> > receive some
other number, then it's a violation of R5RS for for- <BR>> > each to
behave the way 359.100 did; but for Schemes like Bigloo <BR>> >
that have coercion rules that take a multi-value return to a single- <BR>>
> value context, it's not a violation.<BR>> ><BR>> >
-jacob<BR>> ><BR>> > (I actually wrote up a version of this before
and then deleted it, <BR>> > thinking it was too technical for
anybody to care about ... looks <BR>> > like I was wrong. :)
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