Bio.Iteratee.Iteratee

Monadic and General Iteratees: incremental input parsers, processors and transformers

Types

type EnumerateeHandler eli elo m a = (Stream eli -> Iteratee eli m a) -> SomeException -> Iteratee elo m (Iteratee eli m a)

Error handling

throwErr :: SomeException -> Iteratee s m a

Report and propagate an unrecoverable error. Disregard the input first and then propagate the error. This error cannot be handled by enumFromCallbackCatch, although it can be cleared by checkErr.

throwRecoverableErr :: SomeException -> (Stream s -> Iteratee s m a) -> Iteratee s m a

Report and propagate a recoverable error. This error can be handled by both enumFromCallbackCatch and checkErr.

checkErr :: NullPoint s => Iteratee s m a -> Iteratee s m (Either SomeException a)

Check if an iteratee produces an error. Returns Right a if it completes without errors, otherwise Left SomeException. checkErr is useful for iteratees that may not terminate, such as Data.Iteratee.head with an empty stream.

Basic Iteratees

unitIter :: NullPoint s => Iteratee s m ()

The identity iteratee. Doesn't do any processing of input.

skipToEof :: Iteratee s m ()

Skip the rest of the stream

isStreamFinished :: Nullable s => Iteratee s m (Maybe SomeException)

Get the stream status of an iteratee.

Iteratee composition

mBind :: Monad m => m a -> (a -> Iteratee s m b) -> Iteratee s m b infixl 1

Lifts a monadic action and combines it with a continuation. mBind m f is the same as lift m >>= f, but does not require a Nullable constraint on the stream type.

mBind_ :: Monad m => m a -> Iteratee s m b -> Iteratee s m b infixl 1

Lifts a monadic action, ignored the result and combines it with a continuation. mBind_ m f is the same as lift m >>= f, but does not require a Nullable constraint on the stream type.

ioBind :: MonadIO m => IO a -> (a -> Iteratee s m b) -> Iteratee s m b infixl 1

Lifts an IO action and combines it with a continuation. ioBind m f is the same as liftIO m >>= f, but does not require a Nullable constraint on the stream type.

ioBind_ :: MonadIO m => IO a -> Iteratee s m b -> Iteratee s m b infixl 1

Lifts an IO action, ignores its result, and combines it with a continuation. ioBind_ m f is the same as liftIO m >> f, but does not require a Nullable constraint on the stream type.

Chunkwise Iteratees

mapChunksM_ :: (Monad m, Nullable s) => (s -> m b) -> Iteratee s m ()

Map a monadic function over the chunks of the stream and ignore the result. Useful for creating efficient monadic iteratee consumers, e.g.

 logger = mapChunksM_ (liftIO . putStrLn)

these can be efficiently run in parallel with other iteratees via Data.Iteratee.ListLike.zip.

foldChunksM :: (Monad m, Nullable s) => (a -> s -> m a) -> a -> Iteratee s m a

A fold over chunks

getChunk :: Nullable s => Iteratee s m s

Get the current chunk from the stream.

getChunks :: Nullable s => Iteratee s m [s]

Get a list of all chunks from the stream.

Nested iteratee combinators

mapChunks :: NullPoint s => (s -> s') -> Enumeratee s s' m a

Convert one stream into another with the supplied mapping function. This function operates on whole chunks at a time, contrasting to mapStream which operates on single elements.

unpacker :: Enumeratee B.ByteString [Word8] m a
unpacker = mapChunks B.unpack

mapChunksM :: (Monad m, NullPoint s) => (s -> m s') -> Enumeratee s s' m a

Convert a stream of s to a stream of s' using the supplied function.

convStream :: (Monad m, Nullable s) => Iteratee s m s' -> Enumeratee s s' m a

Convert one stream into another, not necessarily in lockstep.

The transformer mapStream maps one element of the outer stream to one element of the nested stream. The transformer below is more general: it may take several elements of the outer stream to produce one element of the inner stream, or the other way around. The transformation from one stream to the other is specified as Iteratee s m s'.

unfoldConvStream :: (Monad m, Nullable s) => (acc -> Iteratee s m (acc, s')) -> acc -> Enumeratee s s' m a

The most general stream converter. Given a function to produce iteratee transformers and an initial state, convert the stream using iteratees generated by the function while continually updating the internal state.

unfoldConvStreamCheck :: (Monad m, Nullable elo) => (((Stream eli -> Iteratee eli m a) -> Maybe SomeException -> Iteratee elo m (Iteratee eli m a)) -> Enumeratee elo eli m a) -> (acc -> Iteratee elo m (acc, eli)) -> acc -> Enumeratee elo eli m a

joinI :: (Monad m, Nullable s) => Iteratee s m (Iteratee s' m a) -> Iteratee s m a

Collapse a nested iteratee. The inner iteratee is terminated by EOF. Errors are propagated through the result.

The stream resumes from the point of the outer iteratee; any remaining input in the inner iteratee will be lost. Differs from join in that the inner iteratee is terminated, and may have a different stream type than the result.

joinIM :: Monad m => m (Iteratee s m a) -> Iteratee s m a

Lift an iteratee inside a monad to an iteratee.

Enumerators

type Enumerator s m a = Iteratee s m a -> m (Iteratee s m a)

Each enumerator takes an iteratee and returns an iteratee

an Enumerator is an iteratee transformer. The enumerator normally stops when the stream is terminated or when the iteratee moves to the done state, whichever comes first. When to stop is of course up to the enumerator...

type Enumeratee sFrom sTo m a = Iteratee sTo m a -> Iteratee sFrom m (Iteratee sTo m a)

Basic enumerators

enumChunk :: Monad m => Stream s -> Enumerator s m a

Applies the iteratee to the given stream. This wraps enumEof, enumErr, and enumPure1Chunk, calling the appropriate enumerator based upon Stream.

enumEof :: Monad m => Enumerator s m a

The most primitive enumerator: applies the iteratee to the terminated stream. The result is the iteratee in the Done state. It is an error if the iteratee does not terminate on EOF.

enumErr :: (Exception e, Monad m) => e -> Enumerator s m a

Another primitive enumerator: tell the Iteratee the stream terminated with an error.

enumPure1Chunk :: Monad m => s -> Enumerator s m a

The pure 1-chunk enumerator

It passes a given list of elements to the iteratee in one chunk This enumerator does no IO and is useful for testing of base parsing

enumList :: Monad m => [s] -> Enumerator s m a

Enumerate chunks from a list

enumCheckIfDone :: Monad m => Iteratee s m a -> m (Bool, Iteratee s m a)

Checks if an iteratee has finished.

This enumerator runs the iteratee, performing any monadic actions. If the result is True, the returned iteratee is done.

enumFromCallback :: (Monad m, NullPoint s) => (st -> m (Either SomeException ((Bool, st), s))) -> st -> Enumerator s m a

Create an enumerator from a callback function

enumFromCallbackCatch :: (IException e, Monad m, NullPoint s) => (st -> m (Either SomeException ((Bool, st), s))) -> (e -> m (Maybe EnumException)) -> st -> Enumerator s m a

Create an enumerator from a callback function with an exception handler. The exception handler is called if an iteratee reports an exception.

Enumerator Combinators

eneeCheckIfDone :: (Monad m, NullPoint elo) => ((Stream eli -> Iteratee eli m a) -> Iteratee elo m (Iteratee eli m a)) -> Enumeratee elo eli m a

Utility function for creating enumeratees. Typical usage is demonstrated by the breakE definition.

breakE
  :: (Monad m, LL.ListLike s el, NullPoint s)
  => (el -> Bool)
  -> Enumeratee s s m a
breakE cpred = eneeCheckIfDone (liftI . step)
 where
  step k (Chunk s)
      | LL.null s  = liftI (step k)
      | otherwise  = case LL.break cpred s of
        (str', tail')
          | LL.null tail' -> eneeCheckIfDone (liftI . step) . k $ Chunk str'
          | otherwise     -> idone (k $ Chunk str') (Chunk tail')
  step k stream           =  idone (k stream) stream

eneeCheckIfDoneHandle :: NullPoint elo => EnumerateeHandler eli elo m a -> ((Stream eli -> Iteratee eli m a) -> Maybe SomeException -> Iteratee elo m (Iteratee eli m a)) -> Enumeratee elo eli m a

The same as eneeCheckIfDonePass, with one extra argument: a handler which is used to process any exceptions in a separate method.

eneeCheckIfDoneIgnore :: NullPoint elo => ((Stream eli -> Iteratee eli m a) -> Maybe SomeException -> Iteratee elo m (Iteratee eli m a)) -> Enumeratee elo eli m a

eneeCheckIfDonePass :: NullPoint elo => ((Stream eli -> Iteratee eli m a) -> Maybe SomeException -> Iteratee elo m (Iteratee eli m a)) -> Enumeratee elo eli m a

mergeEnums

Arguments

:: (Nullable s2, Nullable s1, Monad m)

=> Enumerator s1 m a

inner enumerator

-> Enumerator s2 (Iteratee s1 m) a

outer enumerator

-> Enumeratee s2 s1 (Iteratee s1 m) a

merging enumeratee

-> Enumerator s1 m a

Combine enumeration over two streams. The merging enumeratee would typically be the result of merge or mergeByChunks (see merge for example).

Enumeratee Combinators

($=) :: Monad m => (forall a. Enumerator s m a) -> Enumeratee s s' m b -> Enumerator s' m b infixl 1

Combines Enumerator which produces stream of s and Enumeratee which transforms stream of s to stream of s' to into Enumerator which produces stream of s'

(=$) :: (Nullable s, Monad m) => Enumeratee s s' m a -> Iteratee s' m a -> Iteratee s m a infixr 0

Combines an Enumeratee from s to s' and an Iteratee that consumes s' into an Iteratee which consumes s

(><>) :: (Nullable s1, Monad m) => (forall x. Enumeratee s1 s2 m x) -> Enumeratee s2 s3 m a -> Enumeratee s1 s3 m a

Enumeratee composition Run the second enumeratee within the first. In this example, stream2list is run within the 'takeStream 10', which is itself run within 'takeStream 15', resulting in 15 elements being consumed

>>> run =<< enumPure1Chunk [1..1000 :: Int] (joinI $ (I.takeStream 15 ><> I.takeStream 10) I.stream2list)
[1,2,3,4,5,6,7,8,9,10]

(<><) :: (Nullable s1, Monad m) => Enumeratee s2 s3 m a -> (forall x. Enumeratee s1 s2 m x) -> Enumeratee s1 s3 m a

enumeratee composition with the arguments flipped, see ><>

Misc.

seek :: NullPoint s => FileOffset -> Iteratee s m ()

Seek to a position in the stream

Classes

module Bio.Iteratee.Base