Safe Haskell  None 

Higherlevel 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] > Pipe l i a u m ()
 sourceNull :: Monad m => GSource m a
 unfold :: Monad m => (b > Maybe (a, b)) > b > GSource m a
 enumFromTo :: (Enum a, Eq a, Monad m) => a > a > GSource m a
 iterate :: Monad m => (a > a) > a > GSource m a
 fold :: Monad m => (b > a > b) > b > GSink a m b
 foldMap :: (Monad m, Monoid b) => (a > b) > GSink a m b
 take :: Monad m => Int > GSink a m [a]
 drop :: Monad m => Int > GSink a m ()
 head :: Monad m => GSink a m (Maybe a)
 peek :: Monad m => GLSink a m (Maybe a)
 consume :: Monad m => GSink a m [a]
 sinkNull :: Monad m => GInfSink a m
 foldM :: Monad m => (b > a > m b) > b > GSink a m b
 mapM_ :: Monad m => (a > m ()) > GInfSink a m
 map :: Monad m => (a > b) > GInfConduit a m b
 mapMaybe :: Monad m => (a > Maybe b) > GInfConduit a m b
 catMaybes :: Monad m => GInfConduit (Maybe a) m a
 concatMap :: Monad m => (a > [b]) > GInfConduit a m b
 concatMapAccum :: Monad m => (a > accum > (accum, [b])) > accum > GInfConduit a m b
 groupBy :: Monad m => (a > a > Bool) > GInfConduit a m [a]
 isolate :: Monad m => Int > GConduit a m a
 filter :: Monad m => (a > Bool) > GInfConduit a m a
 mapM :: Monad m => (a > m b) > GInfConduit a m b
 iterM :: Monad m => (a > m ()) > GInfConduit a m a
 mapMaybeM :: Monad m => (a > m (Maybe b)) > GInfConduit a m b
 concatMapM :: Monad m => (a > m [b]) > GInfConduit a m b
 concatMapAccumM :: Monad m => (a > accum > m (accum, [b])) > accum > GInfConduit a m b
 sequence :: Monad m => GLSink i m o > GLInfConduit i m o
Sources
sourceList :: Monad m => [a] > Pipe l i a u m ()Source
Convert a list into a source.
Since 0.3.0
sourceNull :: Monad m => GSource m aSource
A source that outputs no values. Note that this is just a typerestricted
synonym for mempty
.
Since 0.3.0
unfold :: Monad m => (b > Maybe (a, b)) > b > GSource m aSource
Generate a source from a seed value.
Since 0.4.2
enumFromTo :: (Enum a, Eq a, Monad m) => a > a > GSource m aSource
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
iterate :: Monad m => (a > a) > a > GSource m aSource
Produces an infinite stream of repeated applications of f to x.
Sinks
Pure
foldMap :: (Monad m, Monoid b) => (a > b) > GSink a m bSource
A monoidal strict left fold.
Since 0.5.3
take :: Monad m => Int > GSink 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
Since 0.3.0
drop :: Monad m => Int > GSink 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.
Since 0.3.0
head :: Monad m => GSink a m (Maybe a)Source
Take a single value from the stream, if available.
Since 0.3.0
peek :: Monad m => GLSink 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.
Since 0.3.0
consume :: Monad m => GSink 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.
Since 0.3.0
sinkNull :: Monad m => GInfSink a mSource
Ignore the remainder of values in the source. Particularly useful when
combined with isolate
.
Since 0.3.0
Monadic
foldM :: Monad m => (b > a > m b) > b > GSink a m bSource
A monadic strict left fold.
Since 0.3.0
mapM_ :: Monad m => (a > m ()) > GInfSink a mSource
Apply the action to all values in the stream.
Since 0.3.0
Conduits
Pure
map :: Monad m => (a > b) > GInfConduit a m bSource
Apply a transformation to all values in a stream.
Since 0.3.0
mapMaybe :: Monad m => (a > Maybe b) > GInfConduit a m bSource
Apply a transformation that may fail to all values in a stream, discarding the failures.
Since 0.5.1
catMaybes :: Monad m => GInfConduit (Maybe a) m aSource
Filter the Just
values from a stream, discarding the Nothing
values.
Since 0.5.1
concatMap :: Monad m => (a > [b]) > GInfConduit a m bSource
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 > GInfConduit a m bSource
concatMap
with an accumulator.
Since 0.3.0
groupBy :: Monad m => (a > a > Bool) > GInfConduit a m [a]Source
Grouping input according to an equality function.
Since 0.3.0
isolate :: Monad m => Int > GConduit 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 ...
Since 0.3.0
filter :: Monad m => (a > Bool) > GInfConduit a m aSource
Keep only values in the stream passing a given predicate.
Since 0.3.0
Monadic
mapM :: Monad m => (a > m b) > GInfConduit 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
sideeffects of running the action, see mapM_
.
Since 0.3.0
iterM :: Monad m => (a > m ()) > GInfConduit a m aSource
Apply a monadic action on all values in a stream.
This Conduit
can be used to perform a monadic sideeffect for every
value, whilst passing the value through the Conduit
asis.
iterM f = mapM (\a > f a >>= \() > return a)
Since 0.5.6
mapMaybeM :: Monad m => (a > m (Maybe b)) > GInfConduit a m bSource
Apply a monadic transformation that may fail to all values in a stream, discarding the failures.
Since 0.5.1
concatMapM :: Monad m => (a > m [b]) > GInfConduit a m bSource
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 > GInfConduit a m bSource
concatMapM
with an accumulator.
Since 0.3.0
Misc
:: Monad m  
=> GLSink i m o 

> GLInfConduit i m o 
Run a Pipe
repeatedly, and output its result value downstream. Stops
when no more input is available from upstream.
Since 0.5.0