Data.LBool

Lifted boolean type.

Documentation

data LBool

Lifted Bool type. It has three values lTrue, lFalse, lUndef.

Instances

Eq LBool

Show LBool

lTrue :: LBool

lifted true value

lFalse :: LBool

lifted false value

lUndef :: LBool

undefined truth value

lnot :: LBool -> LBool

   lnot lTrue == lFalse
   lnot lFalse == lTrue
   lnot lUndef == lUndef

liftBool :: Bool -> LBool

   liftBool True == lTrue
   liftBool False == lFalse

unliftBool :: LBool -> Maybe Bool

   unliftBool lTrue == Just True
   unliftBool lFalse == Just False
   unliftBool lUndef == Nothing