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Re: [Scheme-reports] multiple values module

On Tue, May 24, 2011 at 6:02 PM, John Cowan <cowan@x> wrote:
Emmanuel Medernach scripsit:

>   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.
> Therefore code relying on this cannot be portable, isn't it ?

No, it's not portable.

Indeed, but in (foo X Y) I would not allow the evaluation of _expression_ X to interfere with Y : if X is (values X1 X2) and Y is (values), foo could mislead X1 with X and X2 with Y as in some implementation. I mean doesn't the report has to specify that evaluation of X has to be bound to X only ?

> As you say, some implementation reifies 'values'.  However the
> R[567]RS definition of values currently forbids to reify it as I
> understand it :
>   (values obj ...) procedure Delivers all of its arguments to its
>   continuation.

It doesn't say *how* they are delivered.  Reification is a perfectly
legitimate strategy.  


Historically, multiple values were intended to be
a more lightweight alternative to constructing an object:

Yes, like "letting values on the stack" implementations.
There is a last colon in your mail, is it truncated ?

Best regards,
Emmanuel Medernach
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