help need

[Benny]

type Poly = [Float]   addPoly::Poly->Poly->Poly addPoly x y = zipWith (+) x y   instance (Float a) => Num (Poly a) where                    x + y = addPoly x y     I got the "Cannot use type synonym in instance head" error message when I was trying to compile the above code. Can you tell me why and how to solve it?   Cheers   Benny