Data.Conduit.Combinators

This module is meant as a replacement for Data.Conduit.List. That module follows a naming scheme which was originally inspired by its enumerator roots. This module is meant to introduce a naming scheme which encourages conduit best practices.

There are two versions of functions in this module. Those with a trailing E work in the individual elements of a chunk of data, e.g., the bytes of a ByteString, the Chars of a Text, or the Ints of a Vector Int. Those without a trailing E work on unchunked streams.

FIXME: discuss overall naming, usage of mono-traversable, etc

Mention take (Conduit) vs drop (Consumer)

Producers

Pure

yieldMany :: (Monad m, MonoFoldable mono) => mono -> ConduitT i (Element mono) m ()

Yield each of the values contained by the given MonoFoldable.

This will work on many data structures, including lists, ByteStrings, and Vectors.

Subject to fusion

Since: 1.3.0

unfold :: Monad m => (b -> Maybe (a, b)) -> b -> ConduitT i a m ()

Generate a producer from a seed value.

Subject to fusion

Since: 1.3.0

enumFromTo :: (Monad m, Enum a, Ord a) => a -> a -> ConduitT i a m ()

Enumerate from a value to a final value, inclusive, via succ.

This is generally more efficient than using Prelude's enumFromTo and combining with sourceList since this avoids any intermediate data structures.

Subject to fusion

Since: 1.3.0

iterate :: Monad m => (a -> a) -> a -> ConduitT i a m ()

Produces an infinite stream of repeated applications of f to x.

Subject to fusion

Since: 1.3.0

repeat :: Monad m => a -> ConduitT i a m ()

Produce an infinite stream consisting entirely of the given value.

Subject to fusion

Since: 1.3.0

replicate :: Monad m => Int -> a -> ConduitT i a m ()

Produce a finite stream consisting of n copies of the given value.

Subject to fusion

Since: 1.3.0

sourceLazy :: (Monad m, LazySequence lazy strict) => lazy -> ConduitT i strict m ()

Generate a producer by yielding each of the strict chunks in a LazySequence.

For more information, see toChunks.

Subject to fusion

Since: 1.3.0

Monadic

repeatM :: Monad m => m a -> ConduitT i a m ()

Repeatedly run the given action and yield all values it produces.

Subject to fusion

Since: 1.3.0

repeatWhileM :: Monad m => m a -> (a -> Bool) -> ConduitT i a m ()

Repeatedly run the given action and yield all values it produces, until the provided predicate returns False.

Subject to fusion

Since: 1.3.0

replicateM :: Monad m => Int -> m a -> ConduitT i a m ()

Perform the given action n times, yielding each result.

Subject to fusion

Since: 1.3.0

I/O

sourceFile :: MonadResource m => FilePath -> ConduitT i ByteString m ()

Stream the contents of a file as binary data.

Since: 1.3.0

sourceFileBS :: MonadResource m => FilePath -> ConduitT i ByteString m ()

sourceFile specialized to ByteString to help with type inference.

Since: 1.3.0

sourceHandle :: MonadIO m => Handle -> ConduitT i ByteString m ()

Stream the contents of a Handle as binary data. Note that this function will not automatically close the Handle when processing completes, since it did not acquire the Handle in the first place.

Since: 1.3.0

sourceHandleUnsafe :: MonadIO m => Handle -> ConduitT i ByteString m ()

Same as sourceHandle, but instead of allocating a new buffer for each incoming chunk of data, reuses the same buffer. Therefore, the ByteStrings yielded by this function are not referentially transparent between two different yields.

This function will be slightly more efficient than sourceHandle by avoiding allocations and reducing garbage collections, but should only be used if you can guarantee that you do not reuse a ByteString (or any slice thereof) between two calls to await.

Since: 1.3.0

sourceIOHandle :: MonadResource m => IO Handle -> ConduitT i ByteString m ()

An alternative to sourceHandle. Instead of taking a pre-opened Handle, it takes an action that opens a Handle (in read mode), so that it can open it only when needed and close it as soon as possible.

Since: 1.3.0

stdin :: MonadIO m => ConduitT i ByteString m ()

sourceHandle applied to stdin.

Subject to fusion

Since: 1.3.0

withSourceFile :: (MonadUnliftIO m, MonadIO n) => FilePath -> (ConduitM i ByteString n () -> m a) -> m a

Like withBinaryFile, but provides a source to read bytes from.

Since: 1.3.0

Filesystem

sourceDirectory :: MonadResource m => FilePath -> ConduitT i FilePath m ()

Stream the contents of the given directory, without traversing deeply.

This function will return all of the contents of the directory, whether they be files, directories, etc.

Note that the generated filepaths will be the complete path, not just the filename. In other words, if you have a directory foo containing files bar and baz, and you use sourceDirectory on foo, the results will be foo/bar and foo/baz.

Since: 1.3.0

sourceDirectoryDeep

Arguments

:: MonadResource m

=> Bool

Follow directory symlinks

-> FilePath

Root directory

-> ConduitT i FilePath m ()

Deeply stream the contents of the given directory.

This works the same as sourceDirectory, but will not return directories at all. This function also takes an extra parameter to indicate whether symlinks will be followed.

Since: 1.3.0

Consumers

Pure

drop :: Monad m => Int -> ConduitT a o m ()

Ignore a certain number of values in the stream.

Note: since this function doesn't produce anything, you probably want to use it with (>>) instead of directly plugging it into a pipeline:

>>> runConduit $ yieldMany [1..5] .| drop 2 .| sinkList
[]
>>> runConduit $ yieldMany [1..5] .| (drop 2 >> sinkList)
[3,4,5]

Since: 1.3.0

dropE :: (Monad m, IsSequence seq) => Index seq -> ConduitT seq o m ()

Drop a certain number of elements from a chunked stream.

Note: you likely want to use it with monadic composition. See the docs for drop.

Since: 1.3.0

dropWhile :: Monad m => (a -> Bool) -> ConduitT a o m ()

Drop all values which match the given predicate.

Note: you likely want to use it with monadic composition. See the docs for drop.

Since: 1.3.0

dropWhileE :: (Monad m, IsSequence seq) => (Element seq -> Bool) -> ConduitT seq o m ()

Drop all elements in the chunked stream which match the given predicate.

Note: you likely want to use it with monadic composition. See the docs for drop.

Since: 1.3.0

fold :: (Monad m, Monoid a) => ConduitT a o m a

Monoidally combine all values in the stream.

Subject to fusion

Since: 1.3.0

foldE :: (Monad m, MonoFoldable mono, Monoid (Element mono)) => ConduitT mono o m (Element mono)

Monoidally combine all elements in the chunked stream.

Subject to fusion

Since: 1.3.0

foldl :: Monad m => (a -> b -> a) -> a -> ConduitT b o m a

A strict left fold.

Subject to fusion

Since: 1.3.0

foldl1 :: Monad m => (a -> a -> a) -> ConduitT a o m (Maybe a)

A strict left fold with no starting value. Returns Nothing when the stream is empty.

Subject to fusion

foldlE :: (Monad m, MonoFoldable mono) => (a -> Element mono -> a) -> a -> ConduitT mono o m a

A strict left fold on a chunked stream.

Subject to fusion

Since: 1.3.0

foldMap :: (Monad m, Monoid b) => (a -> b) -> ConduitT a o m b

Apply the provided mapping function and monoidal combine all values.

Subject to fusion

Since: 1.3.0

foldMapE :: (Monad m, MonoFoldable mono, Monoid w) => (Element mono -> w) -> ConduitT mono o m w

Apply the provided mapping function and monoidal combine all elements of the chunked stream.

Subject to fusion

Since: 1.3.0

all :: Monad m => (a -> Bool) -> ConduitT a o m Bool

Check that all values in the stream return True.

Subject to shortcut logic: at the first False, consumption of the stream will stop.

Subject to fusion

Since: 1.3.0

allE :: (Monad m, MonoFoldable mono) => (Element mono -> Bool) -> ConduitT mono o m Bool

Check that all elements in the chunked stream return True.

Subject to shortcut logic: at the first False, consumption of the stream will stop.

Subject to fusion

Since: 1.3.0

any :: Monad m => (a -> Bool) -> ConduitT a o m Bool

Check that at least one value in the stream returns True.

Subject to shortcut logic: at the first True, consumption of the stream will stop.

Subject to fusion

Since: 1.3.0

anyE :: (Monad m, MonoFoldable mono) => (Element mono -> Bool) -> ConduitT mono o m Bool

Check that at least one element in the chunked stream returns True.

Subject to shortcut logic: at the first True, consumption of the stream will stop.

Subject to fusion

Since: 1.3.0

and :: Monad m => ConduitT Bool o m Bool

Are all values in the stream True?

Consumption stops once the first False is encountered.

Subject to fusion

Since: 1.3.0

andE :: (Monad m, MonoFoldable mono, Element mono ~ Bool) => ConduitT mono o m Bool

Are all elements in the chunked stream True?

Consumption stops once the first False is encountered.

Subject to fusion

Since: 1.3.0

or :: Monad m => ConduitT Bool o m Bool

Are any values in the stream True?

Consumption stops once the first True is encountered.

Subject to fusion

Since: 1.3.0

orE :: (Monad m, MonoFoldable mono, Element mono ~ Bool) => ConduitT mono o m Bool

Are any elements in the chunked stream True?

Consumption stops once the first True is encountered.

Subject to fusion

Since: 1.3.0

asum :: (Monad m, Alternative f) => ConduitT (f a) o m (f a)

Alternatively combine all values in the stream.

Since: 1.3.0

elem :: (Monad m, Eq a) => a -> ConduitT a o m Bool

Are any values in the stream equal to the given value?

Stops consuming as soon as a match is found.

Subject to fusion

Since: 1.3.0

elemE :: (Monad m, IsSequence seq, Eq (Element seq)) => Element seq -> ConduitT seq o m Bool

Are any elements in the chunked stream equal to the given element?

Stops consuming as soon as a match is found.

Subject to fusion

Since: 1.3.0

notElem :: (Monad m, Eq a) => a -> ConduitT a o m Bool

Are no values in the stream equal to the given value?

Stops consuming as soon as a match is found.

Subject to fusion

Since: 1.3.0

notElemE :: (Monad m, IsSequence seq, Eq (Element seq)) => Element seq -> ConduitT seq o m Bool

Are no elements in the chunked stream equal to the given element?

Stops consuming as soon as a match is found.

Subject to fusion

Since: 1.3.0

sinkLazy :: (Monad m, LazySequence lazy strict) => ConduitT strict o m lazy

Consume all incoming strict chunks into a lazy sequence. Note that the entirety of the sequence will be resident at memory.

This can be used to consume a stream of strict ByteStrings into a lazy ByteString, for example.

Subject to fusion

Since: 1.3.0

sinkList :: Monad m => ConduitT a o m [a]

Consume all values from the stream and return as a list. Note that this will pull all values into memory.

Subject to fusion

Since: 1.3.0

sinkVector :: (Vector v a, PrimMonad m) => ConduitT a o m (v a)

Sink incoming values into a vector, growing the vector as necessary to fit more elements.

Note that using this function is more memory efficient than sinkList and then converting to a Vector, as it avoids intermediate list constructors.

Subject to fusion

Since: 1.3.0

sinkVectorN

Arguments

:: (Vector v a, PrimMonad m)

=> Int

maximum allowed size

-> ConduitT a o m (v a)

Sink incoming values into a vector, up until size maxSize. Subsequent values will be left in the stream. If there are less than maxSize values present, returns a Vector of smaller size.

Note that using this function is more memory efficient than sinkList and then converting to a Vector, as it avoids intermediate list constructors.

Subject to fusion

Since: 1.3.0

sinkLazyBuilder :: Monad m => ConduitT Builder o m ByteString

Same as sinkBuilder, but afterwards convert the builder to its lazy representation.

Alternatively, this could be considered an alternative to sinkLazy, with the following differences:

• This function will allow multiple input types, not just the strict version of the lazy structure.
• Some buffer copying may occur in this version.

Subject to fusion

Since: 1.3.0

sinkNull :: Monad m => ConduitT a o m ()

Consume and discard all remaining values in the stream.

Subject to fusion

Since: 1.3.0

awaitNonNull :: (Monad m, MonoFoldable a) => ConduitT a o m (Maybe (NonNull a))

Same as await, but discards any leading onull values.

Since: 1.3.0

head :: Monad m => ConduitT a o m (Maybe a)

Take a single value from the stream, if available.

Since: 1.3.0

headDef :: Monad m => a -> ConduitT a o m a

Same as head, but returns a default value if none are available from the stream.

Since: 1.3.0

headE :: (Monad m, IsSequence seq) => ConduitT seq o m (Maybe (Element seq))

Get the next element in the chunked stream.

Since: 1.3.0

peek :: Monad m => ConduitT a o m (Maybe a)

View the next value in the stream without consuming it.

Since: 1.3.0

peekE :: (Monad m, MonoFoldable mono) => ConduitT mono o m (Maybe (Element mono))

View the next element in the chunked stream without consuming it.

Since: 1.3.0

last :: Monad m => ConduitT a o m (Maybe a)

Retrieve the last value in the stream, if present.

Subject to fusion

Since: 1.3.0

lastDef :: Monad m => a -> ConduitT a o m a

Same as last, but returns a default value if none are available from the stream.

Since: 1.3.0

lastE :: (Monad m, IsSequence seq) => ConduitT seq o m (Maybe (Element seq))

Retrieve the last element in the chunked stream, if present.

Subject to fusion

Since: 1.3.0

length :: (Monad m, Num len) => ConduitT a o m len

Count how many values are in the stream.

Subject to fusion

Since: 1.3.0

lengthE :: (Monad m, Num len, MonoFoldable mono) => ConduitT mono o m len

Count how many elements are in the chunked stream.

Subject to fusion

Since: 1.3.0

lengthIf :: (Monad m, Num len) => (a -> Bool) -> ConduitT a o m len

Count how many values in the stream pass the given predicate.

Subject to fusion

Since: 1.3.0

lengthIfE :: (Monad m, Num len, MonoFoldable mono) => (Element mono -> Bool) -> ConduitT mono o m len

Count how many elements in the chunked stream pass the given predicate.

Subject to fusion

Since: 1.3.0

maximum :: (Monad m, Ord a) => ConduitT a o m (Maybe a)

Get the largest value in the stream, if present.

Subject to fusion

Since: 1.3.0

maximumE :: (Monad m, IsSequence seq, Ord (Element seq)) => ConduitT seq o m (Maybe (Element seq))

Get the largest element in the chunked stream, if present.

Subject to fusion

Since: 1.3.0

minimum :: (Monad m, Ord a) => ConduitT a o m (Maybe a)

Get the smallest value in the stream, if present.

Subject to fusion

Since: 1.3.0

minimumE :: (Monad m, IsSequence seq, Ord (Element seq)) => ConduitT seq o m (Maybe (Element seq))

Get the smallest element in the chunked stream, if present.

Subject to fusion

Since: 1.3.0

null :: Monad m => ConduitT a o m Bool

True if there are no values in the stream.

This function does not modify the stream.

Since: 1.3.0

nullE :: (Monad m, MonoFoldable mono) => ConduitT mono o m Bool

True if there are no elements in the chunked stream.

This function may remove empty leading chunks from the stream, but otherwise will not modify it.

Since: 1.3.0

sum :: (Monad m, Num a) => ConduitT a o m a

Get the sum of all values in the stream.

Subject to fusion

Since: 1.3.0

sumE :: (Monad m, MonoFoldable mono, Num (Element mono)) => ConduitT mono o m (Element mono)

Get the sum of all elements in the chunked stream.

Subject to fusion

Since: 1.3.0

product :: (Monad m, Num a) => ConduitT a o m a

Get the product of all values in the stream.

Subject to fusion

Since: 1.3.0

productE :: (Monad m, MonoFoldable mono, Num (Element mono)) => ConduitT mono o m (Element mono)

Get the product of all elements in the chunked stream.

Subject to fusion

Since: 1.3.0

find :: Monad m => (a -> Bool) -> ConduitT a o m (Maybe a)

Find the first matching value.

Subject to fusion

Since: 1.3.0

Monadic

mapM_ :: Monad m => (a -> m ()) -> ConduitT a o m ()

Apply the action to all values in the stream.

Note: if you want to pass the values instead of consuming them, use iterM instead.

Subject to fusion

Since: 1.3.0

mapM_E :: (Monad m, MonoFoldable mono) => (Element mono -> m ()) -> ConduitT mono o m ()

Apply the action to all elements in the chunked stream.

Note: the same caveat as with mapM_ applies. If you don't want to consume the values, you can use iterM:

iterM (omapM_ f)

Subject to fusion

Since: 1.3.0

foldM :: Monad m => (a -> b -> m a) -> a -> ConduitT b o m a

A monadic strict left fold.

Subject to fusion

Since: 1.3.0

foldME :: (Monad m, MonoFoldable mono) => (a -> Element mono -> m a) -> a -> ConduitT mono o m a

A monadic strict left fold on a chunked stream.

Subject to fusion

Since: 1.3.0

foldMapM :: (Monad m, Monoid w) => (a -> m w) -> ConduitT a o m w

Apply the provided monadic mapping function and monoidal combine all values.

Subject to fusion

Since: 1.3.0

foldMapME :: (Monad m, MonoFoldable mono, Monoid w) => (Element mono -> m w) -> ConduitT mono o m w

Apply the provided monadic mapping function and monoidal combine all elements in the chunked stream.

Subject to fusion

Since: 1.3.0

I/O

sinkFile :: MonadResource m => FilePath -> ConduitT ByteString o m ()

Stream all incoming data to the given file.

Since: 1.3.0

sinkFileCautious :: MonadResource m => FilePath -> ConduitM ByteString o m ()

Cautious version of sinkFile. The idea here is to stream the values to a temporary file in the same directory of the destination file, and only on successfully writing the entire file, moves it atomically to the destination path.

In the event of an exception occurring, the temporary file will be deleted and no move will be made. If the application shuts down without running exception handling (such as machine failure or a SIGKILL), the temporary file will remain and the destination file will be untouched.

Since: 1.3.0

sinkTempFile

Arguments

:: MonadResource m

=> FilePath

temp directory

-> String

filename pattern

-> ConduitM ByteString o m FilePath

Stream data into a temporary file in the given directory with the given filename pattern, and return the temporary filename. The temporary file will be automatically deleted when exiting the active ResourceT block, if it still exists.

Since: 1.3.0

sinkSystemTempFile

Arguments

:: MonadResource m

=> String

filename pattern

-> ConduitM ByteString o m FilePath

Same as sinkTempFile, but will use the default temp file directory for the system as the first argument.

Since: 1.3.0

sinkFileBS :: MonadResource m => FilePath -> ConduitT ByteString o m ()

sinkFile specialized to ByteString to help with type inference.

Since: 1.3.0

sinkHandle :: MonadIO m => Handle -> ConduitT ByteString o m ()

Stream all incoming data to the given Handle. Note that this function does not flush and will not close the Handle when processing completes.

Since: 1.3.0

sinkIOHandle :: MonadResource m => IO Handle -> ConduitT ByteString o m ()

An alternative to sinkHandle. Instead of taking a pre-opened Handle, it takes an action that opens a Handle (in write mode), so that it can open it only when needed and close it as soon as possible.

Since: 1.3.0

print :: (Show a, MonadIO m) => ConduitT a o m ()

Print all incoming values to stdout.

Subject to fusion

Since: 1.3.0

stdout :: MonadIO m => ConduitT ByteString o m ()

sinkHandle applied to stdout.

Subject to fusion

Since: 1.3.0

stderr :: MonadIO m => ConduitT ByteString o m ()

sinkHandle applied to stderr.

Subject to fusion

Since: 1.3.0

withSinkFile :: (MonadUnliftIO m, MonadIO n) => FilePath -> (ConduitM ByteString o n () -> m a) -> m a

Like withBinaryFile, but provides a sink to write bytes to.

Since: 1.3.0

withSinkFileBuilder :: (MonadUnliftIO m, MonadIO n) => FilePath -> (ConduitM Builder o n () -> m a) -> m a

Same as withSinkFile, but lets you use a Builder.

Since: 1.3.0

withSinkFileCautious :: (MonadUnliftIO m, MonadIO n) => FilePath -> (ConduitM ByteString o n () -> m a) -> m a

Like sinkFileCautious, but uses the with pattern instead of MonadResource.

Since: 1.3.0

sinkHandleBuilder :: MonadIO m => Handle -> ConduitM Builder o m ()

Stream incoming builders, executing them directly on the buffer of the given Handle. Note that this function does not automatically close the Handle when processing completes. Pass flush to flush the buffer.

Since: 1.3.0

sinkHandleFlush :: MonadIO m => Handle -> ConduitM (Flush ByteString) o m ()

Stream incoming Flushes, executing them on IO.Handle Note that this function does not automatically close the Handle when processing completes

Since: 1.3.0

Transformers

Pure

map :: Monad m => (a -> b) -> ConduitT a b m ()

Apply a transformation to all values in a stream.

Subject to fusion

Since: 1.3.0

mapE :: (Monad m, Functor f) => (a -> b) -> ConduitT (f a) (f b) m ()

Apply a transformation to all elements in a chunked stream.

Subject to fusion

Since: 1.3.0

omapE :: (Monad m, MonoFunctor mono) => (Element mono -> Element mono) -> ConduitT mono mono m ()

Apply a monomorphic transformation to all elements in a chunked stream.

Unlike mapE, this will work on types like ByteString and Text which are MonoFunctor but not Functor.

Subject to fusion

Since: 1.3.0

concatMap :: (Monad m, MonoFoldable mono) => (a -> mono) -> ConduitT a (Element mono) m ()

Apply the function to each value in the stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMap, mapMaybe, and mapFoldable.

Subject to fusion

Since: 1.3.0

concatMapE :: (Monad m, MonoFoldable mono, Monoid w) => (Element mono -> w) -> ConduitT mono w m ()

Apply the function to each element in the chunked stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMap, mapMaybe, and mapFoldable.

Subject to fusion

Since: 1.3.0

take :: Monad m => Int -> ConduitT a a m ()

Stream up to n number of values downstream.

Note that, if downstream terminates early, not all values will be consumed. If you want to force exactly the given number of values to be consumed, see takeExactly.

Subject to fusion

Since: 1.3.0

takeE :: (Monad m, IsSequence seq) => Index seq -> ConduitT seq seq m ()

Stream up to n number of elements downstream in a chunked stream.

Note that, if downstream terminates early, not all values will be consumed. If you want to force exactly the given number of values to be consumed, see takeExactlyE.

Since: 1.3.0

takeWhile :: Monad m => (a -> Bool) -> ConduitT a a m ()

Stream all values downstream that match the given predicate.

Same caveats regarding downstream termination apply as with take.

Since: 1.3.0

takeWhileE :: (Monad m, IsSequence seq) => (Element seq -> Bool) -> ConduitT seq seq m ()

Stream all elements downstream that match the given predicate in a chunked stream.

Same caveats regarding downstream termination apply as with takeE.

Since: 1.3.0

takeExactly :: Monad m => Int -> ConduitT a b m r -> ConduitT a b m r

Consume precisely the given number of values and feed them downstream.

This function is in contrast to take, which will only consume up to the given number of values, and will terminate early if downstream terminates early. This function will discard any additional values in the stream if they are unconsumed.

Note that this function takes a downstream ConduitT as a parameter, as opposed to working with normal fusion. For more information, see http://www.yesodweb.com/blog/2013/10/core-flaw-pipes-conduit, the section titled "pipes and conduit: isolate".

Since: 1.3.0

takeExactlyE :: (Monad m, IsSequence a) => Index a -> ConduitT a b m r -> ConduitT a b m r

Same as takeExactly, but for chunked streams.

Since: 1.3.0

concat :: (Monad m, MonoFoldable mono) => ConduitT mono (Element mono) m ()

Flatten out a stream by yielding the values contained in an incoming MonoFoldable as individually yielded values.

Subject to fusion

Since: 1.3.0

filter :: Monad m => (a -> Bool) -> ConduitT a a m ()

Keep only values in the stream passing a given predicate.

Subject to fusion

Since: 1.3.0

filterE :: (IsSequence seq, Monad m) => (Element seq -> Bool) -> ConduitT seq seq m ()

Keep only elements in the chunked stream passing a given predicate.

Subject to fusion

Since: 1.3.0

mapWhile :: Monad m => (a -> Maybe b) -> ConduitT a b m ()

Map values as long as the result is Just.

Since: 1.3.0

conduitVector

Arguments

:: (Vector v a, PrimMonad m)

=> Int

maximum allowed size

-> ConduitT a (v a) m ()

Break up a stream of values into vectors of size n. The final vector may be smaller than n if the total number of values is not a strict multiple of n. No empty vectors will be yielded.

Since: 1.3.0

scanl :: Monad m => (a -> b -> a) -> a -> ConduitT b a m ()

Analog of scanl for lists.

Subject to fusion

Since: 1.3.0

mapAccumWhile :: Monad m => (a -> s -> Either s (s, b)) -> s -> ConduitT a b m s

mapWhile with a break condition dependent on a strict accumulator. Equivalently, mapAccum as long as the result is Right. Instead of producing a leftover, the breaking input determines the resulting accumulator via Left.

Subject to fusion

concatMapAccum :: Monad m => (a -> accum -> (accum, [b])) -> accum -> ConduitT a b m ()

concatMap with an accumulator.

Subject to fusion

Since: 1.3.0

intersperse :: Monad m => a -> ConduitT a a m ()

Insert the given value between each two values in the stream.

Subject to fusion

Since: 1.3.0

slidingWindow :: (Monad m, IsSequence seq, Element seq ~ a) => Int -> ConduitT a seq m ()

Sliding window of values 1,2,3,4,5 with window size 2 gives [1,2],[2,3],[3,4],[4,5]

Best used with structures that support O(1) snoc.

Subject to fusion

Since: 1.3.0

chunksOfE :: (Monad m, IsSequence seq) => Index seq -> ConduitT seq seq m ()

Split input into chunk of size chunkSize

The last element may be smaller than the chunkSize (see also chunksOfExactlyE which will not yield this last element)

Since: 1.3.0

chunksOfExactlyE :: (Monad m, IsSequence seq) => Index seq -> ConduitT seq seq m ()

Split input into chunk of size chunkSize

If the input does not split into chunks exactly, the remainder will be leftover (see also chunksOfE)

Since: 1.3.0

Monadic

mapM :: Monad m => (a -> m b) -> ConduitT a b m ()

Apply a monadic transformation to all values in a stream.

If you do not need the transformed values, and instead just want the monadic side-effects of running the action, see mapM_.

Subject to fusion

Since: 1.3.0

mapME :: (Monad m, Traversable f) => (a -> m b) -> ConduitT (f a) (f b) m ()

Apply a monadic transformation to all elements in a chunked stream.

Subject to fusion

Since: 1.3.0

omapME :: (Monad m, MonoTraversable mono) => (Element mono -> m (Element mono)) -> ConduitT mono mono m ()

Apply a monadic monomorphic transformation to all elements in a chunked stream.

Unlike mapME, this will work on types like ByteString and Text which are MonoFunctor but not Functor.

Subject to fusion

Since: 1.3.0

concatMapM :: (Monad m, MonoFoldable mono) => (a -> m mono) -> ConduitT a (Element mono) m ()

Apply the monadic function to each value in the stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMapM, mapMaybeM, and mapFoldableM.

Subject to fusion

Since: 1.3.0

filterM :: Monad m => (a -> m Bool) -> ConduitT a a m ()

Keep only values in the stream passing a given monadic predicate.

Subject to fusion

Since: 1.3.0

filterME :: (Monad m, IsSequence seq) => (Element seq -> m Bool) -> ConduitT seq seq m ()

Keep only elements in the chunked stream passing a given monadic predicate.

Subject to fusion

Since: 1.3.0

iterM :: Monad m => (a -> m ()) -> ConduitT a a m ()

Apply a monadic action on all values in a stream.

This Conduit can be used to perform a monadic side-effect for every value, whilst passing the value through the Conduit as-is.

iterM f = mapM (\a -> f a >>= \() -> return a)

Subject to fusion

Since: 1.3.0

scanlM :: Monad m => (a -> b -> m a) -> a -> ConduitT b a m ()

Analog of scanl for lists, monadic.

Subject to fusion

Since: 1.3.0

mapAccumWhileM :: Monad m => (a -> s -> m (Either s (s, b))) -> s -> ConduitT a b m s

Monadic mapAccumWhile.

Subject to fusion

concatMapAccumM :: Monad m => (a -> accum -> m (accum, [b])) -> accum -> ConduitT a b m ()

concatMapM with an accumulator.

Subject to fusion

Since: 1.3.0

Textual

encodeUtf8 :: (Monad m, Utf8 text binary) => ConduitT text binary m ()

Encode a stream of text as UTF8.

Subject to fusion

Since: 1.3.0

decodeUtf8 :: MonadThrow m => ConduitT ByteString Text m ()

Decode a stream of binary data as UTF8.

Since: 1.3.0

decodeUtf8Lenient :: Monad m => ConduitT ByteString Text m ()

Decode a stream of binary data as UTF8, replacing any invalid bytes with the Unicode replacement character.

Since: 1.3.0

line :: (Monad m, IsSequence seq, Element seq ~ Char) => ConduitT seq o m r -> ConduitT seq o m r

Stream in the entirety of a single line.

Like takeExactly, this will consume the entirety of the line regardless of the behavior of the inner Conduit.

Since: 1.3.0

lineAscii :: (Monad m, IsSequence seq, Element seq ~ Word8) => ConduitT seq o m r -> ConduitT seq o m r

Same as line, but operates on ASCII/binary data.

Since: 1.3.0

unlines :: (Monad m, IsSequence seq, Element seq ~ Char) => ConduitT seq seq m ()

Insert a newline character after each incoming chunk of data.

Subject to fusion

Since: 1.3.0

unlinesAscii :: (Monad m, IsSequence seq, Element seq ~ Word8) => ConduitT seq seq m ()

Same as unlines, but operates on ASCII/binary data.

Subject to fusion

Since: 1.3.0

takeExactlyUntilE :: (Monad m, IsSequence seq) => (Element seq -> Bool) -> ConduitT seq o m r -> ConduitT seq o m r

Stream in the chunked input until an element matches a predicate.

Like takeExactly, this will consume the entirety of the prefix regardless of the behavior of the inner Conduit.

linesUnbounded :: (Monad m, IsSequence seq, Element seq ~ Char) => ConduitT seq seq m ()

Convert a stream of arbitrarily-chunked textual data into a stream of data where each chunk represents a single line. Note that, if you have unknown or untrusted input, this function is unsafe, since it would allow an attacker to form lines of massive length and exhaust memory.

Subject to fusion

Since: 1.3.0

linesUnboundedAscii :: (Monad m, IsSequence seq, Element seq ~ Word8) => ConduitT seq seq m ()

Same as linesUnbounded, but for ASCII/binary data.

Subject to fusion

Since: 1.3.0

splitOnUnboundedE :: (Monad m, IsSequence seq) => (Element seq -> Bool) -> ConduitT seq seq m ()

Split a stream of arbitrarily-chunked data, based on a predicate on elements. Elements that satisfy the predicate will cause chunks to be split, and aren't included in these output chunks. Note that, if you have unknown or untrusted input, this function is unsafe, since it would allow an attacker to form chunks of massive length and exhaust memory.

Builders

builderToByteString :: PrimMonad m => ConduitT Builder ByteString m ()

Incrementally execute builders and pass on the filled chunks as bytestrings.

Since: 1.3.0

unsafeBuilderToByteString :: PrimMonad m => ConduitT Builder ByteString m ()

Incrementally execute builders on the given buffer and pass on the filled chunks as bytestrings. Note that, if the given buffer is too small for the execution of a build step, a larger one will be allocated.

WARNING: This conduit yields bytestrings that are NOT referentially transparent. Their content will be overwritten as soon as control is returned from the inner sink!

Since: 1.3.0

builderToByteStringWith :: PrimMonad m => BufferAllocStrategy -> ConduitT Builder ByteString m ()

A conduit that incrementally executes builders and passes on the filled chunks as bytestrings to an inner sink.

INV: All bytestrings passed to the inner sink are non-empty.

Since: 1.3.0

builderToByteStringFlush :: PrimMonad m => ConduitT (Flush Builder) (Flush ByteString) m ()

Same as builderToByteString, but input and output are wrapped in Flush.

Since: 1.3.0

builderToByteStringWithFlush :: PrimMonad m => BufferAllocStrategy -> ConduitT (Flush Builder) (Flush ByteString) m ()

Since: 1.3.0

type BufferAllocStrategy = (IO Buffer, Int -> Buffer -> IO (IO Buffer))

A buffer allocation strategy (buf0, nextBuf) specifies the initial buffer to use and how to compute a new buffer nextBuf minSize buf with at least size minSize from a filled buffer buf. The double nesting of the IO monad helps to ensure that the reference to the filled buffer buf is lost as soon as possible, but the new buffer doesn't have to be allocated too early.

Since: 1.3.0

allNewBuffersStrategy :: Int -> BufferAllocStrategy

The simplest buffer allocation strategy: whenever a buffer is requested, allocate a new one that is big enough for the next build step to execute.

NOTE that this allocation strategy may spill quite some memory upon direct insertion of a bytestring by the builder. Thats no problem for garbage collection, but it may lead to unreasonably high memory consumption in special circumstances.

Since: 1.3.0

reuseBufferStrategy :: IO Buffer -> BufferAllocStrategy

An unsafe, but possibly more efficient buffer allocation strategy: reuse the buffer, if it is big enough for the next build step to execute.

Since: 1.3.0

Special

vectorBuilder

Arguments

:: (PrimMonad m, PrimMonad n, Vector v e, PrimState m ~ PrimState n)

=> Int

size

-> ((e -> n ()) -> ConduitT i Void m r)

-> ConduitT i (v e) m r

Generally speaking, yielding values from inside a Conduit requires some allocation for constructors. This can introduce an overhead, similar to the overhead needed to represent a list of values instead of a vector. This overhead is even more severe when talking about unboxed values.

This combinator allows you to overcome this overhead, and efficiently fill up vectors. It takes two parameters. The first is the size of each mutable vector to be allocated. The second is a function. The function takes an argument which will yield the next value into a mutable vector.

Under the surface, this function uses a number of tricks to get high performance. For more information on both usage and implementation, please see: https://www.fpcomplete.com/user/snoyberg/library-documentation/vectorbuilder

Since: 1.3.0

mapAccumS :: Monad m => (a -> s -> ConduitT b Void m s) -> s -> ConduitT () b m () -> ConduitT a Void m s

Consume a source with a strict accumulator, in a way piecewise defined by a controlling stream. The latter will be evaluated until it terminates.

>>> let f a s = liftM (:s) $ mapC (*a) =$ CL.take a
>>> reverse $ runIdentity $ yieldMany [0..3] $$ mapAccumS f [] (yieldMany [1..])
[[],[1],[4,6],[12,15,18]] :: [[Int]]

peekForever :: Monad m => ConduitT i o m () -> ConduitT i o m ()

Run a consuming conduit repeatedly, only stopping when there is no more data available from upstream.

Since: 1.3.0

peekForeverE :: (Monad m, MonoFoldable i) => ConduitT i o m () -> ConduitT i o m ()

Run a consuming conduit repeatedly, only stopping when there is no more data available from upstream.

In contrast to peekForever, this function will ignore empty chunks of data. So for example, if a stream of data contains an empty ByteString, it is still treated as empty, and the consuming function is not called.

Since: 1.3.0