Why does the code below not pass the type checker? If I could explictly parameterize y with the type constructor Id (as e.g. in System F), then 'y Id' should have the type Int -> Int and hence "y Id x" should be OK, but with Haskell's implicit type parameters it does not work. So, how can I make this work? Klaus ------------ type Id a = a x :: Id Int x = undefined y :: (a Int) -> (a Int) y = undefined test = y x Error: Couldn't match expected type `a Int' against inferred type `Id Int' In the first argument of `y', namely `x' In the expression: y x In the definition of `test': test = y x -- View this message in context: http://www.nabble.com/Question-about-kinds-tp17701553p17701553.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.