{- CSE 341.  Y combinator in Haskell (with unsafeCoerce to make it work) -}

import Unsafe.Coerce

-- y won't typecheck in Haskell because it would require an infinite type.
-- However, we can convince Haskell to accept it anyway using unsafeCoerce

y :: (a -> a) -> a
y = \f -> (\x -> f (unsafeCoerce x x)) (\x -> f (unsafeCoerce x x))

-- and here is a factorial definition using the genuine y combinator:
fact = y (\f -> (\n -> if n==0 then 1 else n*f (n-1)))