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