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Re: call with value

From: William ML Leslie
Subject: Re: call with value
Date: Mon, 13 Apr 2020 12:34:51 +1000

On Mon, 13 Apr 2020 at 02:59, Stefan Israelsson Tampe
<address@hidden> wrote:
> I have this (on guile 3.0.0),
> (define (f x) (call-with-values (lambda () x) (case-lambda ((x) ...) (x 
> ...)))))
> and the code does not simplify to (define (f x) x), why?
> It would be great to have guile optimize this as in python we have
> x=1,0
> => x=(1,0)
> And the great thing with python on guile is that we get the same behavior 
> with (values 1 0) as a r.h.s. so that we get good interoperability between 
> guile and python.

Hi Stis,

I'm not sure if I mentioned this to you earlier, but I'm worried that
this won't be a great user experience.  When a python function returns
a tuple, whether "implicitly" as part of the return statement or not,
the invoker still gets one tuple, and is free to unpack it.  If I were
to call a function that returned a 1-value tuple and instead it got
unpacked for me, I would be very confused.

Similarly, if a python function `f` returns a tuple and I invoke
`g(f(x))`, I expect g to receive one tuple; not a number of arguments.
I'd have to say `g(*f(x))` if I wanted it to receive the items as
argument values.

William Leslie

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