Re: Bugs with GADTs in GHC6.4.1

On 12 Dec 2005, at 12:48, Andres Loeh wrote:

> > The attached script induces panic in GHC6.4.1: "ghc-6.4.1: panic! (the
> > `impossible' happened, GHC version 6.4.1): applyTypeToArgs f{v a1Eg}
> > x{v a1Ei}".
>
> I think this is related to a known bug, because the same workaround
> helps -- annotate the "f" and "x" arguments in the last line of your
> program with dummy type variables, and the program will be accepted:
>
> > zap :: Vector n (a -> b) -> Vector n a -> Vector n b
> > zap fs xs = unfoldv f (len fs) (VP (fs, xs)) where
> >   f :: VectorPair (a->b) a (S n) -> (b, VectorPair (a->b) a n)
> >   f (VP (VCons (f :: foo) fs, VCons (x :: bar) xs)) = (f x, VP (fs, 
> > xs))

Thanks, Andres. As you say, that solve the problem.
Jeremy

Jeremy.Gibbons@xxxxxxxxxxxxxxx
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transpose4+.lhs
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