I'm trying: instance Num b => Num (a -> b) where fromInteger = pure . Prelude.fromInteger negate = fmap Prelude.negate (+) = liftA2 (Prelude.+) (*) = liftA2 (Prelude.*) abs = fmap Prelude.abs signum = fmap Prelude.signum but the compiler rejects it with: src\Main.hs:24:9: Could not deduce (Show (a -> b), Eq (a -> b)) from the context (Num b) arising from the superclasses of an instance declaration at src\Main.hs:24:9-29 Possible fix: add (Show (a -> b), Eq (a -> b)) to the context of the instance declaration or add an instance declaration for (Show (a -> b), Eq (a -> b)) In the instance declaration for `Num (a -> b)' Could someone please explain this to me? I thought that it might be that it couldn't work out the functions necessary for (a->b) to be in the classes Show and Eq - so I tried adding definitions for == ans show, but it made no difference. Thanks