Edward Kmett 쓴 글:
Actually the problem lies in your definition of fz, it has the wrong
type to be used in lam.
The Z you get out of fz as type Z b String, but you need it to have Z (a
-> b) String so that when you strip off the Z you have a Y String (a ->
b) matching the result type of lam.
To get there replace your definition of fz with:
> fz :: Z a String -> Z (a -> b) String
> fz = Z . Y . unY . f . unZ
I think this seems to be the Yeoh wanted.
Mine was just blinded hack just to make it type check without looking at
what program means.
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