[Haskell] Haskell type containing no non-_|_ values?

Hello, probably a trivial question: Is there a type in Haskell that contains only the undefined value _|_? The polymorphic type (forall a. a) has this property, but it seems it cannot be used, e.g., in a tuple:

x :: (Int,(forall a. a)) x = (3,undefined)

leads to errors both in Hugs and GHC. I guess I can help myself out using newtype:

newtype T = T (forall a. a)

x :: (Int,T) x = (3,undefined)

but would like to do without. Is there a way? Thanks, Janis. -- Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de