type Maybe a { Just a | Nothing }

fromMaybe : a (Maybe a) -- a
          =: [
    { case
        | Just    -> dip(drop)
        | Nothing ->
    }
]

join : (Maybe (Maybe a)) -- (Maybe a)
     =: [
    { case
        | Just ->
        | Nothing -> Nothing
    }
]

isJust : (Maybe a) -- Bool
       =: [
    { case
        | Just -> drop True
        | Nothing -> False
    }
]

isNothing : (Maybe a) -- Bool
          =: [
    { case
        | Nothing -> True
        | Just -> drop False
    }
]