[Haskell-cafe] Polykinded promoted types

Gautier DI FOLCO gautier.difolco at gmail.com
Wed Dec 10 22:37:22 UTC 2014


2014-12-10 21:32 GMT+01:00 Richard Eisenberg <eir at cis.upenn.edu>:

> Escape what, exactly? I'm not sure what your end goal is, so I don't know
> what you're trying to escape from.
>
> Is this what you want?
>
> data List where
>   Nil :: List
>   Cons :: a -> b -> List
>
> type Foo = Cons True (Cons "x" (Cons () Nil))
>
>
> That works, but isn't very useful in practice, I don't think...
>

Escape from this trouble.
When I try to apply a type family on it, I get a forall k, isn't there a
way to "set" it?

Thanks,
Regards.
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