combine :: Alternative f => (forall a. Data a => a -> f r)
                         -> (forall a. Data a => a -> f r)
                         -> (forall a. Data a => a -> f r)
combine f g x = f x <|> g x
combine :: Alternative f => (forall a. Data a => a -> f r)
                         -> (forall a. Data a => a -> f r)
                         -> (forall a. Data a => a -> f r)
combine f g x = f x <|> g x
combine f g x = f x <|> g x