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Re: [Scheme-reports] Multiple values
50 minutes ago, John Cowan wrote:
> Eli Barzilay scripsit:
> > And BTW, as long as I gave the above example, and was dragged to
> > quote the relevant part of R5RS, I can just as well continue the
> > quote:
> > Except for continuations created by the call-with-values
> > procedure, all continuations take exactly one value.
> > and it should be clear now why Chibi's implementation is just
> > plain broken:
> You know that is not true. How dare you say such a thing?
I gave the code that needs to work according to r5rs:
> (define (v . xs)
(call-with-current-continuation (lambda (k) (apply k xs))))
> (call-with-values (lambda () (v 1 2 3)) list)
ERROR on line 64 of file ./lib/init.scm: too many args
Furthermore, R5RS explicitly says:
`values' might be defined as follows:
(define (values . things)
(lambda (cont) (apply cont things))))
but that doesn't work in Chibi either.
> > If you want to get pickier, then all implementations that don't barf
> > at
> > (list 1 (values 2 3 4) 5)
> > are broken because according to R5RS:
> > (values obj ...)
> > Delivers all of its arguments to its continuation. Except for
> > continuations created by the call-with-values procedure, all
> > continuations take exactly one value.
> If R5RS said "Except for [...], all continuations must signal an
> error if they do not receive exactly one value", then you'd be
> right. It doesn't and you aren't.
So the question is what happens when, for example, a continuation that
takes two values is used with one value, and the lack of an explicit
"signal an error"...
> I suppose next you will inform me that (car #f) and (cons 1 2 3) are
> also compelled to signal errors?
...not by that language, but yes, I would consider a scheme that
doesn't to be broken...
> > | Chibi's use cases just aren't anything like Racket's.
> > was just irrelevant nonsense,
> You are entitled to consider it irrelevant to your concerns.
...and I would consider such implementations broken regardless of what
racket does, and more than that, how regardless of how close their use
cases are to Racket's.
> > (And yes, "Ultimately, if you want R6RS, you know where to find it."
> > is wrong too, but who's counting?)
> And I'm done with you. It's a pity, because I've learned things
> from you, but you are going out of your way to make yourself
> offensive, and I see no reason to stand for it.
I'm getting out of my way to point something that should be considered
broken. I don't consider that offensive. It's a pity that you do.
> I adopt this harsh and public mode of denunciation to make my
> intentions unmistakably clear.
And that's a fine example for how r7rs goes so far.
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!
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