[Haskell-cafe] Aren't type system extensions fun? [Further
a.biurvOir4 at asuhan.com
Thu May 29 05:51:47 EDT 2008
Roberto Zunino-2 wrote:
> Alas, for code like yours:
> foo = \f -> (f 'J', f True)
> there are infinite valid types too:
> (forall a. a -> Int) -> (Int, Int)
> (forall a. a -> Char)-> (Char, Char)
> (forall a. a -> (a,a)) -> ((Char,Char),(Bool,Bool))
> and it is much less clear if a "best", most general type exists at all.
foo :: (exists. m :: * -> *. forall a. a -> m a) -> (m Char, m Bool)
Not quite Haskell, but seems to cover all of the examples you gave.
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