\begin{slide}{Rang-(2/N)-Polymorphie in GHC}

\url{http://haskell.org/ghc/docs/latest/html/users_guide/other-type-extensions.html}

\begin{verbatim}
{-# language Rank2Types #-}
f2 :: (forall a. a->a) -> Int -> Int
f4 :: Int -> (forall a. a -> a)

{-# language RankNTypes #-}
f3 :: ((forall a. a->a) -> Int) 
    -> Bool -> Bool
\end{verbatim}

Rang: $1 + $ max. Tiefe der $(\Box \to *)$-Kontexte
für Typ-Forall

\end{slide}
