Safe Haskell | Safe-Infered |
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Data.Conduit.List
Description
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 :: Monad m => [a] -> Source m a
- sourceNull :: Monad m => Source m a
- unfold :: Monad m => (b -> Maybe (a, b)) -> b -> Source m a
- enumFromTo :: (Enum a, Eq a, Monad m) => a -> a -> Source m a
- fold :: Monad m => (b -> a -> b) -> b -> Sink a m b
- take :: Monad m => Int -> Sink a m [a]
- drop :: Monad m => Int -> Sink a m ()
- head :: Monad m => Sink a m (Maybe a)
- zip :: Monad m => Source m a -> Source m b -> Source m (a, b)
- zipSinks :: Monad m => Sink i m r -> Sink i m r' -> Sink i m (r, r')
- peek :: Monad m => Sink a m (Maybe a)
- consume :: Monad m => Sink a m [a]
- sinkNull :: Monad m => Sink a m ()
- foldM :: Monad m => (b -> a -> m b) -> b -> Sink a m b
- mapM_ :: Monad m => (a -> m ()) -> Sink a m ()
- map :: Monad m => (a -> b) -> Conduit a m b
- concatMap :: Monad m => (a -> [b]) -> Conduit a m b
- concatMapAccum :: Monad m => (a -> accum -> (accum, [b])) -> accum -> Conduit a m b
- groupBy :: Monad m => (a -> a -> Bool) -> Conduit a m [a]
- isolate :: Monad m => Int -> Conduit a m a
- filter :: Monad 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
- concatMapAccumM :: Monad m => (a -> accum -> m (accum, [b])) -> accum -> Conduit a m b
Sources
sourceList :: Monad m => [a] -> Source m a
Convert a list into a source.
Since 0.3.0
sourceNull :: Monad m => Source m a
A source that returns nothing. Note that this is just a type-restricted
synonym for mempty
.
Since 0.3.0
unfold :: Monad m => (b -> Maybe (a, b)) -> b -> Source m a
Generate a source from a seed value.
Since 0.4.2
enumFromTo :: (Enum a, Eq a, Monad m) => a -> a -> Source m a
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.
Since 0.4.2
Sinks
Pure
take :: Monad m => Int -> Sink a m [a]
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
Since 0.3.0
drop :: Monad m => Int -> Sink a m ()
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.
Since 0.3.0
zip :: Monad m => Source m a -> Source m b -> Source m (a, b)
Combines two sources. The new source will stop producing once either source has been exhausted.
Since 0.3.0
zipSinks :: Monad m => Sink i m r -> Sink i m r' -> Sink i m (r, r')
Combines two sinks. The new sink will complete when both input sinks have completed.
If both sinks finish on the same chunk, and both report leftover input, arbitrarily yield the left sink's leftover input.
Since 0.4.1
peek :: Monad m => Sink a m (Maybe a)
Look at the next value in the stream, if available. This function will not change the state of the stream.
Since 0.3.0
consume :: Monad m => Sink a m [a]
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.
Since 0.3.0
sinkNull :: Monad m => Sink a m ()
Ignore the remainder of values in the source. Particularly useful when
combined with isolate
.
Since 0.3.0
Monadic
mapM_ :: Monad m => (a -> m ()) -> Sink a m ()
Apply the action to all values in the stream.
Since 0.3.0
Pure
map :: Monad m => (a -> b) -> Conduit a m b
Apply a transformation to all values in a stream.
Since 0.3.0
concatMap :: Monad m => (a -> [b]) -> Conduit a m b
Apply a transformation to all values in a stream, concatenating the output values.
Since 0.3.0
concatMapAccum :: Monad m => (a -> accum -> (accum, [b])) -> accum -> Conduit a m b
concatMap
with an accumulator.
Since 0.3.0
groupBy :: Monad m => (a -> a -> Bool) -> Conduit a m [a]
Grouping input according to an equality function.
Since 0.3.0
isolate :: Monad m => Int -> Conduit a m a
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 ...
Since 0.3.0
filter :: Monad m => (a -> Bool) -> Conduit a m a
Keep only values in the stream passing a given predicate.
Since 0.3.0
Monadic
mapM :: Monad m => (a -> m b) -> Conduit a m b
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_
.
Since 0.3.0
concatMapM :: Monad m => (a -> m [b]) -> Conduit a m b
Apply a monadic transformation to all values in a stream, concatenating the output values.
Since 0.3.0
concatMapAccumM :: Monad m => (a -> accum -> m (accum, [b])) -> accum -> Conduit a m b
concatMapM
with an accumulator.
Since 0.3.0