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.

Describe the status of a stream of data.

Monadic iteratee

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.

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.

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.

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

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

NullPoint class. Containers that have a null representation, corresponding to Data.Monoid.mempty.

Nullable container class