-- non primitive if-then-else data Then a = Then a data Else a = Else a then' :: a -> Then a then' = Then else' :: a -> Else a else' = Else if' :: Bool -> Then a -> Else a -> a if' True (Then t) _ = t if' False _ (Else f) = f main = do if' (4 < 3) (then' $ print "foo") (else' $ print "bar") if' (4 > 3) (then' $ print "baz") (else' $ print "bat")