Higher-level functions to interact with the elements of a stream. Most of these are based on list functions.

Note that these functions all deal with individual elements of a stream as a
sort of "black box", where there is no introspection of the contained
elements. Values such as `ByteString`

and `Text`

will likely need to be
treated specially to deal with their contents properly (`Word8`

and `Char`

,
respectively). See the Data.Conduit.Binary and Data.Conduit.Text
modules.

- sourceList :: Resource m => [a] -> Source m a
- fold :: Resource m => (b -> a -> b) -> b -> Sink a m b
- take :: Resource m => Int -> Sink a m [a]
- drop :: Resource m => Int -> Sink a m ()
- head :: Resource m => Sink a m (Maybe a)
- peek :: Resource m => Sink a m (Maybe a)
- consume :: Resource m => Sink a m [a]
- sinkNull :: Resource m => Sink a m ()
- foldM :: Resource m => (b -> a -> m b) -> b -> Sink a m b
- mapM_ :: Resource m => (a -> m ()) -> Sink a m ()
- map :: Monad m => (a -> b) -> Conduit a m b
- concatMap :: Monad m => (a -> [b]) -> Conduit a m b
- isolate :: Resource m => Int -> Conduit a m a
- filter :: Resource m => (a -> Bool) -> Conduit a m a
- mapM :: Monad m => (a -> m b) -> Conduit a m b
- concatMapM :: Monad m => (a -> m [b]) -> Conduit a m b

# Sources

sourceList :: Resource m => [a] -> Source m aSource

Convert a list into a source.

# Sinks

## Pure

take :: Resource m => Int -> Sink a m [a]Source

Take some values from the stream and return as a list. If you want to
instead create a conduit that pipes data to another sink, see `isolate`

.
This function is semantically equivalent to:

take i = isolate i =$ consume

drop :: Resource m => Int -> Sink a m ()Source

Ignore a certain number of values in the stream. This function is semantically equivalent to:

drop i = take i >> return ()

However, `drop`

is more efficient as it does not need to hold values in
memory.

peek :: Resource m => Sink a m (Maybe a)Source

Look at the next value in the stream, if available. This function will not change the state of the stream.

consume :: Resource m => Sink a m [a]Source

Consume all values from the stream and return as a list. Note that this will pull all values into memory. For a lazy variant, see Data.Conduit.Lazy.

sinkNull :: Resource m => Sink a m ()Source

Ignore the remainder of values in the source. Particularly useful when
combined with `isolate`

.

## Monadic

mapM_ :: Resource m => (a -> m ()) -> Sink a m ()Source

Apply the action to all values in the stream.

## Pure

concatMap :: Monad m => (a -> [b]) -> Conduit a m bSource

Apply a transformation to all values in a stream, concatenating the output values.

isolate :: Resource m => Int -> Conduit a m aSource

Ensure that the inner sink consumes no more than the given number of
values. Note this this does *not* ensure that the sink consumes all of those
values. To get the latter behavior, combine with `sinkNull`

, e.g.:

src $$ do x <- isolate count =$ do x <- someSink sinkNull return x someOtherSink ...

filter :: Resource m => (a -> Bool) -> Conduit a m aSource

Keep only values in the stream passing a given predicate.

## Monadic

mapM :: Monad m => (a -> m b) -> Conduit a m bSource

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_`

.

concatMapM :: Monad m => (a -> m [b]) -> Conduit a m bSource

Apply a monadic transformation to all values in a stream, concatenating the output values.