chunks n xs 
  | n <= length xs = fst (splitAt n xs) : chunks n (tail xs)
  | otherwise      = []
chunks n xs 
  | n <= length xs = fst (splitAt n xs) : chunks n (tail xs)
  | otherwise      = []
chunks n xs 
  | n <= length xs = fst (splitAt n xs) : chunks n (tail xs)
  | otherwise      = []