Benny <[EMAIL PROTECTED]> writes:
> 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? You can either substitute in the type synonym: > instance Num [Float] where > (+) = addPoly Or change Poly to newtype: > newtype Poly = Poly [Float] > addPoly::Poly->Poly->Poly > addPoly (Poly x) (Poly y) = Poly (zipWith (+) x y) HTH > Cheers > Benny Jon Cast _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
