Haskell split a list into fixed-size batches

import Data.List (unfoldr)

chunksOf :: Int -> [a] -> [[a]]
chunksOf n
  | n <= 0 = []
  | otherwise = unfoldr step
  where
    step [] = Nothing
    step xs = Just (splitAt n xs)

batchIndex :: Int -> [a] -> [(Int, [a])]
batchIndex n = zip [0 ..] . chunksOf n