[Haskell-cafe] Re: Flipping *->*->* kinds, or monadic finally-tagless madness

[Ahn, Ki Yung]

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.