Re: values (Re: R5RS)

["Jorgen `forcer' Schaefer" <forcer at mindless dot com>]

Jim Blandy <jimb@red-bean.com> writes:

> > Could you please explain how exactly the implementation given
> > above would break?
> 
> Well:
> And (call-with-values (lambda ()
>                         (call-with-current-continuation
>                           (lambda (k) (k 2 3 4))))
>                       list)
> is (2 3 4), not an error.

Ok, thanks for the explanation :)

[great explanation snipped]

Thanks for this very nice summary :]

> What I'd like is a way to call a function with only as many arguments
> as it expects.  That is, I've got five arguments I could pass, but if
> the function only takes three, that's cool, just pass the first three.
> Then, I could apply this to `values', and return only as many values
> as the caller expects.  So I could have a division function which
> returns the remainder too, but only if the caller was prepared for two
> return values.

Hmm.

I don't know wether i'd like that.  The idea sounds nice, the way
you want to use it sounds nice too, but ... dunno, it passes a
hidden state which sounds ugly.  It also breaks referential
transparency, in a way.

Yes, i consider perls want_array pretty ugly, too.

(btw:
(define (div n1 n2 . r)
  (if (null? r)
      (quotient n1 n2)
      (values (quotient n1 n2)
	      (remainder n1 n2))))

this actually does what you want, without behind-the-scenes-magic, you
just have to pass another argument.  I guess it depends on your
personal tastes which version is nicer.)

	-- forcer

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