data Maybe ('a) where {
    Nothing : Maybe ('a)
    Just : 'a -> Maybe ('a)
};

fromJust : Maybe ('a) -> 'a ;
fromJust a =
    case a of {
        Just a => a
    };

fromMaybe : 'a -> Maybe ('a) -> 'a ;
fromMaybe a b =
    case b of {
        Just a => a;
        Nothing => a
    };

maybe : 'b -> ('a -> 'b) -> Maybe ('a) -> 'b;
maybe b f ma =
    case ma of {
        Just a => f a;
        Nothing => b
    }