{-# Language MultiParamTypeClasses, FlexibleContexts, FlexibleInstances, IncoherentInstances, TypeFamilies, PatternGuards, FunctionalDependencies #-}

import Control.Monad


class MConcat1 a b

    where mConcat1 :: a -> [b]

instance MConcat1 [a] b => MConcat1 [[a]] b

    where mConcat1 x = x >>= mConcat1

instance (a ~ b) => MConcat1 [a] b

    where mConcat1 = id
    

class MConcat2 a b

    where mConcat2 :: a -> Maybe b

instance MConcat2 (Maybe a) b => MConcat2 (Maybe (Maybe a)) b

    where mConcat2 x = x >>= mConcat2

instance (a ~ b) => MConcat2 (Maybe a) b

    where mConcat2 = id



main = do print $ mConcat1 [[[123]],[[345]],[[222],[3333,5555]]]
          print $ mConcat1 [2345]
          
          print $ mConcat2 (Just 123)
          print $ mConcat2 (Just $ Just 345)