[Haskell-cafe] Question, re: type class syntax.

Hi all, I can’t figure out why this is invalid: class (Show a, Num a) => LogTree2 a where evaluator :: (LogTree2 a) t => t -> SizedVector a -> SizedVector a error| ‘LogTree2’ is applied to too many type arguments In the type ‘(LogTree2 a) t => t -> SizedVector a -> SizedVector a’ In the class declaration for ‘LogTree2’ Can anyone help me understand? Thanks, -db