iteratee-0.8.4.2: Iteratee-based I/O

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Data.Iteratee.Iteratee

Contents

Description

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

Synopsis

Types

Error handling

throwErr :: Monad m => SomeException -> Iteratee s m aSource

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

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

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

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

identity :: (Monad m, NullPoint s) => Iteratee s m ()Source

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

skipToEof :: Monad m => Iteratee s m ()Source

Skip the rest of the stream

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

Get the stream status of an iteratee.

Chunkwise Iteratees

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

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.

mapReduceSource

Arguments

:: (Monad m, Nullable s, Monoid b) 
=> Int

maximum number of chunks to read

-> (s -> b)

map function

-> Iteratee s m b 

Perform a parallel map/reduce. The bufsize parameter controls the maximum number of chunks to read at one time. A larger bufsize allows for greater parallelism, but will require more memory.

Implementation of sum

 sum :: (Monad m, LL.ListLike s, Nullable s) => Iteratee s m Int64
 sum = getSum <$> mapReduce 4 (Sum . LL.sum)

getChunk :: (Monad m, Nullable s, NullPoint s) => Iteratee s m sSource

Get the current chunk from the stream.

getChunks :: (Monad m, Nullable s) => Iteratee s m [s]Source

Get a list of all chunks from the stream.

Nested iteratee combinators

mapChunks :: (Monad m, NullPoint s) => (s -> s') -> Enumeratee s s' m aSource

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

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

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 aSource

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.

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

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 aSource

Lift an iteratee inside a monad to an iteratee.

Enumerators

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

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)Source

Basic enumerators

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

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 aSource

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 aSource

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

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

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 aSource

Enumerate chunks from a list

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

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 aSource

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 aSource

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

Enumerator Combinators

(>>>) :: Monad m => Enumerator s m a -> Enumerator s m a -> Enumerator s m aSource

The composition of two enumerators: essentially the functional composition It is convenient to flip the order of the arguments of the composition though: in e1 >>> e2, e1 is executed first

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

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

mergeEnumsSource

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

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

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

>>> run =<< enumPure1Chunk [1..1000 :: Int] (joinI $ (I.take 15 ><> I.take 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 aSource

enumeratee composition with the arguments flipped, see ><>

Misc.

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

Seek to a position in the stream

Classes