iteratee- Iteratee-based I/O

Safe HaskellSafe-Infered




Monadic Iteratees: incremental input parsers, processors and transformers



data Stream c Source

A stream is a (continuing) sequence of elements bundled in Chunks. The first variant indicates termination of the stream. Chunk a gives the currently available part of the stream. The stream is not terminated yet. The case (null Chunk) signifies a stream with no currently available data but which is still continuing. A stream processor should, informally speaking, ``suspend itself'' and wait for more data to arrive.


EOF (Maybe SomeException) 
Chunk c 


Functor Stream

Map a function over a stream.

Typeable1 Stream 
Eq c => Eq (Stream c) 
Show c => Show (Stream c) 
Monoid c => Monoid (Stream c) 

data StreamStatus Source

Describe the status of a stream of data.

Exception types


newtype Iteratee s m a Source

Monadic iteratee




runIter :: forall r. (a -> Stream s -> m r) -> ((Stream s -> Iteratee s m a) -> Maybe SomeException -> m r) -> m r



Control functions

run :: Monad m => Iteratee s m a -> m aSource

Send EOF to the Iteratee and disregard the unconsumed part of the stream. If the iteratee is in an exception state, that exception is thrown with throw. Iteratees that do not terminate on EOF will throw EofException.

tryRun :: (Exception e, Monad m) => Iteratee s m a -> m (Either e a)Source

Run an iteratee, returning either the result or the iteratee exception. Note that only internal iteratee exceptions will be returned; exceptions thrown with Control.Exception.throw or Control.Monad.CatchIO.throw will not be returned.

See IFException for details.

mapIteratee :: (NullPoint s, Monad n, Monad m) => (m a -> n b) -> Iteratee s m a -> Iteratee s n bSource

Transform a computation inside an Iteratee.

ilift :: (Monad m, Monad n) => (forall r. m r -> n r) -> Iteratee s m a -> Iteratee s n aSource

Lift a computation in the inner monad of an iteratee.

A simple use would be to lift a logger iteratee to a monad stack.

 logger :: Iteratee String IO ()
 logger = mapChunksM_ putStrLn
 loggerG :: MonadIO m => Iteratee String m ()
 loggerG = ilift liftIO logger

A more complex example would involve lifting an iteratee to work with interleaved streams. See the example at merge.

ifold :: (Monad m, Monad n) => (forall r. m r -> acc -> n (r, acc)) -> acc -> Iteratee s m a -> Iteratee s n (a, acc)Source

Lift a computation in the inner monad of an iteratee, while threading through an accumulator.

Creating Iteratees

idone :: Monad m => a -> Stream s -> Iteratee s m aSource

liftI :: Monad m => (Stream s -> Iteratee s m a) -> Iteratee s m aSource

idoneM :: Monad m => a -> Stream s -> m (Iteratee s m a)Source

icontM :: Monad m => (Stream s -> Iteratee s m a) -> Maybe SomeException -> m (Iteratee s m a)Source

Stream Functions

setEOF :: Stream c -> SomeExceptionSource

Produce the EOF error message. If the stream was terminated because of an error, keep the error message.