distinctG :: (Ord a, Show a) => a -> (a -> Bool) -> [a] -> Logger (Maybe [a])
distinctG y p as = evalStateT (fun as) Set.empty where
  fun []     = do { pure $ pure [] }
  fun (x:xs) = do
    set <- getT
    if x > y
    then StateT $ \s -> Logger ("fail: " ++ show x) (Nothing, s)
    else do
      set <- getT
      if (x `Set.notMember` set)
      then do
        putT (Set.insert x set)
        case evalStateT (fun xs) set of
          Logger e Nothing -> do
            if p x
            then StateT $ \s -> Logger ("satisfy " ++ show x ++ ";" ++ e) (Nothing, s)
            else StateT $ \s -> Logger e (Nothing, s)
          Logger e (Just rs) -> do
            if p x
            then StateT $ \s -> Logger ("satisfy " ++ show x ++ ";" ++ e) (Just (x : rs), s)
            else StateT $ \s -> Logger e (Just (x : rs), s)
      else do
        case evalStateT (fun xs) set of
          Logger e Nothing -> StateT $ \s -> Logger e (Nothing, s)
          Logger e (Just rs) -> StateT $ \s -> Logger e (Just rs, s)