Haskell Language Streaming IO Streaming IO
Example
io-streams is Stream-based library that focuses on the Stream abstraction but for IO. It exposes two types:
-
InputStream: a read-only smart handle -
OutputStream: a write-only smart handle
We can create a stream with makeInputStream :: IO (Maybe a) -> IO (InputStream a). Reading from a stream is performed using read :: InputStream a -> IO (Maybe a), where Nothing denotes an EOF:
import Control.Monad (forever) import qualified System.IO.Streams as S import System.Random (randomRIO) main :: IO () main = do is <- S.makeInputStream $ randomInt -- create an InputStream forever $ printStream =<< S.read is -- forever read from that stream return () randomInt :: IO (Maybe Int) randomInt = do r <- randomRIO (1, 100) return $ Just r printStream :: Maybe Int -> IO () printStream Nothing = print "Nada!" printStream (Just a) = putStrLn $ show a
