stream-traversal.hs

import Control.Monad
import Data.Foldable
import Data.Sequence ((|>))


data Trav a m r = Trav (a -> m (Trav a m r)) (m r)


chunksOf :: (Applicative m) => ([a] -> m ()) -> Int -> Trav a m ()
chunksOf yield n = go mempty
    where
    go xs' =
        Trav (\x -> do
                  let xs = xs' |> x
                  if length xs >= n
                    then go mempty <$ yield (toList xs)
                    else pure (go xs))
             (when (not (null xs')) (yield (toList xs')))