On Fri, Nov 18, 2005 at 01:31:46PM -0000, Simon Peyton-Jones wrote:
> yes. a newtype declares a new type isomorphic to an existing type.
> newtype T = MkT S
> declares T to be isomorphic to S.
>
> There is no existing Haskell type isomorphic to your Dynamic.
>
> In concrete terms, the newtype constructor is discarded before we get to
> System F; but we can't do that with an existential.
The first argument, but not the second, also applies to
newtype T = MkT (forall a. S)
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