Check if a stream has received EOF.

Read a stream to the end and return all of its elements as a list. This iteratee returns all data from the stream *strictly*.

Read a stream to the end and return all of its elements as a stream. This iteratee returns all data from the stream *strictly*.

Takes an element predicate and returns the (possibly empty) prefix of the stream. None of the characters in the string satisfy the character predicate. If the stream is not terminated, the first character of the remaining stream satisfies the predicate.

N.B. breakE should be used in preference to break. break will retain all data until the predicate is met, which may result in a space leak.

The analogue of List.break

Skip all elements while the predicate is true.

The analogue of List.dropWhile

Drop n elements of the stream, if there are that many.

The analogue of List.drop

Attempt to read the next element of the stream and return it Raise a (recoverable) error if the stream is terminated.

The analogue of List.head

Because head can raise an error, it shouldn't be used when constructing iteratees for convStream. Use tryHead instead.

Similar to head, except it returns Nothing if the stream is terminated.

Attempt to read the last element of the stream and return it Raise a (recoverable) error if the stream is terminated

The analogue of List.last

Given a sequence of characters, attempt to match them against the characters on the stream. Return the count of how many characters matched. The matched characters are removed from the stream. For example, if the stream contains abd, then (heads abc) will remove the characters ab and return 2.

Look ahead at the next element of the stream, without removing it from the stream. Return Just c if successful, return Nothing if the stream is terminated by EOF.

Return a chunk of t elements length while consuming d elements from the stream. Useful for creating a 'rolling average' with convStream.

Return the total length of the remaining part of the stream.

This forces evaluation of the entire stream.

The analogue of List.length

Get the length of the current chunk, or Nothing if EOF.

This function consumes no input.

Take n elements from the current chunk, or the whole chunk if n is greater.

Takes an element predicate and an iteratee, running the iteratee on all elements of the stream until the predicate is met.

the following rule relates break to breakE break pred === joinI (breakE pred stream2stream)

breakE should be used in preference to break whenever possible.

Read n elements from a stream and apply the given iteratee to the stream of the read elements. Unless the stream is terminated early, we read exactly n elements, even if the iteratee has accepted fewer.

The analogue of List.take

Read n elements from a stream and apply the given iteratee to the stream of the read elements. If the given iteratee accepted fewer elements, we stop. This is the variation of take with the early termination of processing of the outer stream once the processing of the inner stream finished early.

Iteratees composed with takeUpTo will consume only enough elements to reach a done state. Any remaining data will be available in the outer stream.

 > let iter = do
 h <- joinI $ takeUpTo 5 I.head
 t <- stream2list
 return (h,t)
 
 > enumPureNChunk [1..10::Int] 3 iter >>= run >>= print
 (1,[2,3,4,5,6,7,8,9,10])
 
 > enumPureNChunk [1..10::Int] 7 iter >>= run >>= print
 (1,[2,3,4,5,6,7,8,9,10])

in each case, I.head consumes only one element, returning the remaining 4 elements to the outer stream

Takes an element predicate and returns the (possibly empty) prefix of the stream. All characters in the string will satisfy the character predicate. If the stream is not terminated, the first character of the remaining stream will not satisfy the predicate.

The analogue of List.takeWhile, see also break and takeWhileE

Takes an element predicate and an iteratee, running the iteratee on all elements of the stream while the predicate is met.

This is preferred to takeWhile.

Map the stream: another iteratee transformer Given the stream of elements of the type el and the function (el->el'), build a nested stream of elements of the type el' and apply the given iteratee to it.

The analog of List.map

Map the stream rigidly.

Like mapStream, but the element type cannot change. This function is necessary for ByteString and similar types that cannot have LooseMap instances, and may be more efficient.

Creates an enumeratee with only elements from the stream that satisfy the predicate function. The outer stream is completely consumed.

The analogue of List.filter

Creates an Enumeratee in which elements from the stream are grouped into sz-sized blocks. The final block may be smaller than sz.

Creates an enumeratee in which elements are grouped into contiguous blocks that are equal according to a predicate.

The analogue of List.groupBy

merge offers another way to nest iteratees: as a monad stack. This allows for the possibility of interleaving data from multiple streams.

 -- print each element from a stream of lines.
 logger :: (MonadIO m) => Iteratee [ByteString] m ()
 logger = mapM_ (liftIO . putStrLn . B.unpack)

 -- combine alternating lines from two sources
 -- To see how this was derived, follow the types from
 -- 'ileaveLines logger' and work outwards.
 run =<< enumFile 10 "file1" (joinI $ enumLinesBS $
           ( enumFile 10 "file2" . joinI . enumLinesBS $ joinI
                 (ileaveLines logger)) >>= run)
 
 ileaveLines :: (Functor m, Monad m)
   => Enumeratee [ByteString] [ByteString] (Iteratee [ByteString] m)
        [ByteString]
 ileaveLines = merge (\l1 l2 ->
    [B.pack "f1:\n\t" ,l1 ,B.pack "f2:\n\t" ,l2 ]
 
 

A version of merge which operates on chunks instead of elements.

mergeByChunks offers more control than merge. merge terminates when the first stream terminates, however mergeByChunks will continue until both streams are exhausted.

mergeByChunks guarantees that both chunks passed to the merge function will have the same number of elements, although that number may vary between calls.

Left-associative fold.

The analogue of List.foldl

Left-associative fold that is strict in the accumulator. This function should be used in preference to foldl whenever possible.

The analogue of List.foldl'.

Variant of foldl with no base case. Requires at least one element in the stream.

The analogue of List.foldl1.

Strict variant of foldl1.

Sum of a stream.

Product of a stream.

The pure n-chunk enumerator It passes a given stream of elements to the iteratee in n-sized chunks.

Enumerate two iteratees over a single stream simultaneously. Deprecated, use zip instead.

Compare to zip.

Enumerate over two iteratees in parallel as long as the first iteratee is still consuming input. The second iteratee will be terminated with EOF when the first iteratee has completed. An example use is to determine how many elements an iteratee has consumed:

 snd <$> enumWith (dropWhile (<5)) length

Compare to zip

Enumerate two iteratees over a single stream simultaneously.

Compare to List.zip.

Enumerate a list of iteratees over a single stream simultaneously and discard the results. This is a different behavior than Prelude's sequence_ which runs iteratees in the list one after the other.

Compare to Prelude.sequence_.

Map a monadic function over the elements of the stream and ignore the result.

The analogue of Control.Monad.foldM