import Prelude hiding ((&&), (||), not)

infixr 3  &&
infixr 2  ||

data Trivalent = TriFalse | TriUnknown | TriTrue deriving (Show, Eq, Ord)

(&&) :: Trivalent -> Trivalent -> Trivalent
TriFalse && _ = TriFalse
_ && TriFalse = TriFalse
TriTrue && TriTrue = TriTrue
_ && _ = TriUnknown

(||) :: Trivalent -> Trivalent -> Trivalent
TriTrue || _ = TriTrue
_ || TriTrue = TriTrue
TriFalse || TriFalse = TriFalse
_ || _ = TriUnknown

not :: Trivalent -> Trivalent
not TriTrue = TriFalse
not TriFalse = TriTrue
not TriUnknown = TriUnknown

main = do
    print $ TriTrue && TriFalse
    print $ not (TriFalse || TriUnknown)
    print $ not (TriUnknown || TriFalse && TriTrue)