On Wed, Dec 15, 2004 at 02:07:10AM -0800, William Lee Irwin III wrote: > This does not work as expected on Complex numbers due to some odd > typechecking hassles apparently associated with abs. How do I get this > to typecheck for both real (e.g. Double) and Complex arguments?
abs :: Num a => a -> a, whereas you want something that returns a Double. You could define class Norm a where norm :: a -> Double instance Norm Float where norm = realToFrac . abs instance Norm Double where norm = abs instance RealFloat a => Norm (Complex a) where norm = realToFrac . magnitude and use norm instead of abs. _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe