Example of two variadic functions in haskell

Vari.hs

import Control.Applicative (liftA2)

class Printf r where
    printf' :: IO () -> r

instance Printf (IO ()) where
    printf' prev = prev >> putStr "\n"

instance Printf a => Printf (Integer -> a) where
    printf' prev = \x -> printf' (prev >> putStr (show x))

printf :: Printf r => r
printf = printf' (pure ())


class PolyOr a r where
    polyOr :: (a -> Bool) -> r

instance PolyOr a (a -> Bool) where
    polyOr f a = f a

instance PolyOr a r => PolyOr a ((a -> Bool) -> r) where
    polyOr f g = polyOr (liftA2 (||) f g)