Den ons. 27. maj 2020 kl. 19.27 skrev George Neuner <gneun...@comcast.net>:

>
> On 5/27/2020 6:34 AM, Jens Axel Søgaard wrote:
> >
> > In standard Racket an application doesn't communicate how many values
> > a function is expected to produce.
>
> You can ask:  see procedure-result-arity
>      https://docs.racket-lang.org/reference/procedures.html


I think  procedure-result-arity  answers the question "how many
values could this procedure return?" and not "how many values
is the procedure expected to return in this context?".


> > I have written a small proof-of-concept of an assignment operator :=
> > that communicates to a function how many extra values it is expected
> > to produce (and still works with standard functions).
> >
> > Are there alternative solutions that are better than the "use a
> > keyword" approach?
>
> You can use  call-with-values  which connects the function that produces
> with the one that consumes, but they have to agree on the number of
> values being passed or it won't work.
>

My problem is that the producer still needs to be told how many values to
produce.

/Jens Axel

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