AnotherStreamingExample.hs

import           Data.Foldable (toList)
import           Streaming
import qualified Streaming.Prelude               as S
import qualified Data.Text                       as T
import qualified Data.Text.IO                    as TIO

main :: IO ()
main =
    withFile "/tmp/source.txt" ReadMode $ \hSource ->
    withFile "/tmp/target.txt" WriteMode $ \hTarget ->
          S.mapM_ (TIO.hPutStrLn hTarget)
        . flip S.for S.each
        . S.filter (\window -> toList window == [T.pack "4",T.pack "6"])
        . S.slidingWindow 2
        . S.untilRight
        $ do atEof <- hIsEOF hSource
             if atEof
                then Right <$> pure ()
                else Left <$> TIO.hGetLine hSource