Safe Haskell  None 

Language  Haskell98 
 data Pipe l i o u m r
 newtype ConduitM i o m r = ConduitM {
 unConduitM :: Pipe i i o () m r
 type Source m o = ConduitM () o m ()
 type Producer m o = forall i. ConduitM i o m ()
 type Sink i = ConduitM i Void
 type Consumer i m r = forall o. ConduitM i o m r
 type Conduit i m o = ConduitM i o m ()
 data ResumableSource m o = ResumableSource (Source m o) (m ())
 data ResumableConduit i m o = ResumableConduit (Conduit i m o) (m ())
 await :: Pipe l i o u m (Maybe i)
 awaitE :: Pipe l i o u m (Either u i)
 awaitForever :: Monad m => (i > Pipe l i o r m r') > Pipe l i o r m r
 yield :: Monad m => o > Pipe l i o u m ()
 yieldM :: Monad m => m o > Pipe l i o u m ()
 yieldOr :: Monad m => o > m () > Pipe l i o u m ()
 leftover :: l > Pipe l i o u m ()
 bracketP :: MonadResource m => IO a > (a > IO ()) > (a > Pipe l i o u m r) > Pipe l i o u m r
 addCleanup :: Monad m => (Bool > m ()) > Pipe l i o u m r > Pipe l i o u m r
 idP :: Monad m => Pipe l a a r m r
 pipe :: Monad m => Pipe l a b r0 m r1 > Pipe Void b c r1 m r2 > Pipe l a c r0 m r2
 pipeL :: Monad m => Pipe l a b r0 m r1 > Pipe b b c r1 m r2 > Pipe l a c r0 m r2
 connectResume :: Monad m => ResumableSource m o > Sink o m r > m (ResumableSource m o, r)
 connectResumeConduit :: Monad m => ResumableConduit i m o > Sink o m r > Sink i m (ResumableConduit i m o, r)
 runPipe :: Monad m => Pipe Void () Void () m r > m r
 injectLeftovers :: Monad m => Pipe i i o u m r > Pipe l i o u m r
 (>+>) :: Monad m => Pipe l a b r0 m r1 > Pipe Void b c r1 m r2 > Pipe l a c r0 m r2
 (<+<) :: Monad m => Pipe Void b c r1 m r2 > Pipe l a b r0 m r1 > Pipe l a c r0 m r2
 fuseLeftovers :: Monad m => ([b] > [a]) > ConduitM a b m () > ConduitM b c m r > ConduitM a c m r
 fuseReturnLeftovers :: Monad m => ConduitM a b m () > ConduitM b c m r > ConduitM a c m (r, [b])
 sourceToPipe :: Monad m => Source m o > Pipe l i o u m ()
 sinkToPipe :: Monad m => Sink i m r > Pipe l i o u m r
 conduitToPipe :: Monad m => Conduit i m o > Pipe l i o u m ()
 toProducer :: Monad m => Source m a > Producer m a
 toConsumer :: Monad m => Sink a m b > Consumer a m b
 catchP :: (MonadBaseControl IO m, Exception e) => Pipe l i o u m r > (e > Pipe l i o u m r) > Pipe l i o u m r
 handleP :: (MonadBaseControl IO m, Exception e) => (e > Pipe l i o u m r) > Pipe l i o u m r > Pipe l i o u m r
 tryP :: (MonadBaseControl IO m, Exception e) => Pipe l i o u m r > Pipe l i o u m (Either e r)
 catchC :: (MonadBaseControl IO m, Exception e) => ConduitM i o m r > (e > ConduitM i o m r) > ConduitM i o m r
 handleC :: (MonadBaseControl IO m, Exception e) => (e > ConduitM i o m r) > ConduitM i o m r > ConduitM i o m r
 tryC :: (MonadBaseControl IO m, Exception e) => ConduitM i o m r > ConduitM i o m (Either e r)
 transPipe :: Monad m => (forall a. m a > n a) > Pipe l i o u m r > Pipe l i o u n r
 mapOutput :: Monad m => (o1 > o2) > Pipe l i o1 u m r > Pipe l i o2 u m r
 mapOutputMaybe :: Monad m => (o1 > Maybe o2) > Pipe l i o1 u m r > Pipe l i o2 u m r
 mapInput :: Monad m => (i1 > i2) > (l2 > Maybe l1) > Pipe l2 i2 o u m r > Pipe l1 i1 o u m r
 sourceList :: Monad m => [a] > Pipe l i a u m ()
 withUpstream :: Monad m => Pipe l i o u m r > Pipe l i o u m (u, r)
 unwrapResumable :: MonadIO m => ResumableSource m o > m (Source m o, m ())
 unwrapResumableConduit :: MonadIO m => ResumableConduit i m o > m (Conduit i m o, m ())
 enumFromTo :: (Enum o, Eq o, Monad m) => o > o > Pipe l i o u m ()
 zipSinks :: Monad m => Sink i m r > Sink i m r' > Sink i m (r, r')
 zipSources :: Monad m => Source m a > Source m b > Source m (a, b)
 zipSourcesApp :: Monad m => Source m (a > b) > Source m a > Source m b
 zipConduitApp :: Monad m => ConduitM i o m (x > y) > ConduitM i o m x > ConduitM i o m y
 passthroughSink :: Monad m => Sink i m r > (r > m ()) > Conduit i m i
Types
The underlying datatype for all the types in this package. In has six type parameters:
 l is the type of values that may be left over from this
Pipe
. APipe
with no leftovers would useVoid
here, and one with leftovers would use the same type as the i parameter. Leftovers are automatically provided to the nextPipe
in the monadic chain.  i is the type of values for this
Pipe
's input stream.  o is the type of values for this
Pipe
's output stream.  u is the result type from the upstream
Pipe
.  m is the underlying monad.
 r is the result type.
A basic intuition is that every Pipe
produces a stream of output values
(o), and eventually indicates that this stream is terminated by sending a
result (r). On the receiving end of a Pipe
, these become the i and u
parameters.
Since 0.5.0
HaveOutput (Pipe l i o u m r) (m ()) o  Provide new output to be sent downstream. This constructor has three
fields: the next 
NeedInput (i > Pipe l i o u m r) (u > Pipe l i o u m r)  Request more input from upstream. The first field takes a new input
value and provides a new 
Done r  Processing with this 
PipeM (m (Pipe l i o u m r))  Require running of a monadic action to get the next 
Leftover (Pipe l i o u m r) l  Return leftover input, which should be provided to future operations. 
MonadRWS r w s m => MonadRWS r w s (Pipe l i o u m)  
MonadBase base m => MonadBase base (Pipe l i o u m)  
MonadError e m => MonadError e (Pipe l i o u m)  
MonadReader r m => MonadReader r (Pipe l i o u m)  
MonadState s m => MonadState s (Pipe l i o u m)  
MonadWriter w m => MonadWriter w (Pipe l i o u m)  
MFunctor (Pipe l i o u)  Since 1.0.4 
MonadTrans (Pipe l i o u)  
Monad m => Monad (Pipe l i o u m)  
Monad m => Functor (Pipe l i o u m)  
Monad m => Applicative (Pipe l i o u m)  
MonadThrow m => MonadThrow (Pipe l i o u m)  
MonadIO m => MonadIO (Pipe l i o u m)  
MonadResource m => MonadResource (Pipe l i o u m)  
Monad m => Monoid (Pipe l i o u m ()) 
newtype ConduitM i o m r Source
Core datatype of the conduit package. This type represents a general
component which can consume a stream of input values i
, produce a stream
of output values o
, perform actions in the m
monad, and produce a final
result r
. The type synonyms provided here are simply wrappers around this
type.
Since 1.0.0
ConduitM  

MonadRWS r w s m => MonadRWS r w s (ConduitM i o m)  
MonadBase base m => MonadBase base (ConduitM i o m)  
MonadError e m => MonadError e (ConduitM i o m)  
MonadReader r m => MonadReader r (ConduitM i o m)  
MonadState s m => MonadState s (ConduitM i o m)  
MonadWriter w m => MonadWriter w (ConduitM i o m)  
MFunctor (ConduitM i o)  
MonadTrans (ConduitM i o)  
Monad m => Monad (ConduitM i o m)  
Monad m => Functor (ConduitM i o m)  
Monad m => Applicative (ConduitM i o m)  
MonadThrow m => MonadThrow (ConduitM i o m)  
MonadIO m => MonadIO (ConduitM i o m)  
MonadResource m => MonadResource (ConduitM i o m)  
Monad m => Monoid (ConduitM i o m ()) 
type Source m o = ConduitM () o m () Source
Provides a stream of output values, without consuming any input or producing a final result.
Since 0.5.0
type Producer m o = forall i. ConduitM i o m () Source
A component which produces a stream of output values, regardless of the
input stream. A Producer
is a generalization of a Source
, and can be
used as either a Source
or a Conduit
.
Since 1.0.0
type Sink i = ConduitM i Void Source
Consumes a stream of input values and produces a final result, without producing any output.
type Sink i m r = ConduitM i Void m r
Since 0.5.0
type Consumer i m r = forall o. ConduitM i o m r Source
A component which consumes a stream of input values and produces a final
result, regardless of the output stream. A Consumer
is a generalization of
a Sink
, and can be used as either a Sink
or a Conduit
.
Since 1.0.0
type Conduit i m o = ConduitM i o m () Source
Consumes a stream of input values and produces a stream of output values, without producing a final result.
Since 0.5.0
data ResumableSource m o Source
A Source
which has been started, but has not yet completed.
This type contains both the current state of the Source
, and the finalizer
to be run to close it.
Since 0.5.0
ResumableSource (Source m o) (m ()) 
MFunctor ResumableSource  Since 1.0.13 
data ResumableConduit i m o Source
A generalization of ResumableSource
. Allows to resume an arbitrary
conduit, keeping its state and using it later (or finalizing it).
Since 1.0.17
ResumableConduit (Conduit i m o) (m ()) 
Primitives
awaitE :: Pipe l i o u m (Either u i) Source
This is similar to await
, but will return the upstream result value as
Left
if available.
Since 0.5.0
awaitForever :: Monad m => (i > Pipe l i o r m r') > Pipe l i o r m r Source
Wait for input forever, calling the given inner Pipe
for each piece of
new input. Returns the upstream result type.
Since 0.5.0
Send a single output value downstream. If the downstream Pipe
terminates, this Pipe
will terminate as well.
Since 0.5.0
Similar to yield
, but additionally takes a finalizer to be run if the
downstream Pipe
terminates.
Since 0.5.0
leftover :: l > Pipe l i o u m () Source
Provide a single piece of leftover input to be consumed by the next pipe in the current monadic binding.
Note: it is highly encouraged to only return leftover values from input already consumed from upstream.
Since 0.5.0
Finalization
bracketP :: MonadResource m => IO a > (a > IO ()) > (a > Pipe l i o u m r) > Pipe l i o u m r Source
Perform some allocation and run an inner Pipe
. Two guarantees are given
about resource finalization:
 It will be prompt. The finalization will be run as early as possible.
 It is exception safe. Due to usage of
resourcet
, the finalization will be run in the event of any exceptions.
Since 0.5.0
:: Monad m  
=> (Bool > m ()) 

> Pipe l i o u m r  
> Pipe l i o u m r 
Add some code to be run when the given Pipe
cleans up.
Since 0.4.1
Composition
pipe :: Monad m => Pipe l a b r0 m r1 > Pipe Void b c r1 m r2 > Pipe l a c r0 m r2 Source
Compose a left and right pipe together into a complete pipe. The left pipe will be automatically closed when the right pipe finishes.
Since 0.5.0
pipeL :: Monad m => Pipe l a b r0 m r1 > Pipe b b c r1 m r2 > Pipe l a c r0 m r2 Source
Same as pipe
, but automatically applies injectLeftovers
to the right Pipe
.
Since 0.5.0
connectResume :: Monad m => ResumableSource m o > Sink o m r > m (ResumableSource m o, r) Source
Connect a Source
to a Sink
until the latter closes. Returns both the
most recent state of the Source
and the result of the Sink
.
We use a ResumableSource
to keep track of the most recent finalizer
provided by the Source
.
Since 0.5.0
connectResumeConduit :: Monad m => ResumableConduit i m o > Sink o m r > Sink i m (ResumableConduit i m o, r) Source
Connect a ResumableConduit
to a sink and return the output of the sink
together with a new ResumableConduit
.
Since 1.0.17
runPipe :: Monad m => Pipe Void () Void () m r > m r Source
Run a pipeline until processing completes.
Since 0.5.0
injectLeftovers :: Monad m => Pipe i i o u m r > Pipe l i o u m r Source
Transforms a Pipe
that provides leftovers to one which does not,
allowing it to be composed.
This function will provide any leftover values within this Pipe
to any
calls to await
. If there are more leftover values than are demanded, the
remainder are discarded.
Since 0.5.0
(>+>) :: Monad m => Pipe l a b r0 m r1 > Pipe Void b c r1 m r2 > Pipe l a c r0 m r2 infixl 9 Source
Fuse together two Pipe
s, connecting the output from the left to the
input of the right.
Notice that the leftover parameter for the Pipe
s must be Void
. This
ensures that there is no accidental data loss of leftovers during fusion. If
you have a Pipe
with leftovers, you must first call injectLeftovers
.
Since 0.5.0
(<+<) :: Monad m => Pipe Void b c r1 m r2 > Pipe l a b r0 m r1 > Pipe l a c r0 m r2 infixr 9 Source
Same as >+>
, but reverse the order of the arguments.
Since 0.5.0
fuseLeftovers :: Monad m => ([b] > [a]) > ConduitM a b m () > ConduitM b c m r > ConduitM a c m r Source
Similar to fuseReturnLeftovers
, but use the provided function to convert
downstream leftovers to upstream leftovers.
Since 1.0.17
fuseReturnLeftovers :: Monad m => ConduitM a b m () > ConduitM b c m r > ConduitM a c m (r, [b]) Source
Same as normal fusion (e.g. =$=
), except instead of discarding leftovers
from the downstream component, return them.
Since 1.0.17
Generalizing
sourceToPipe :: Monad m => Source m o > Pipe l i o u m () Source
sinkToPipe :: Monad m => Sink i m r > Pipe l i o u m r Source
conduitToPipe :: Monad m => Conduit i m o > Pipe l i o u m () Source
toProducer :: Monad m => Source m a > Producer m a Source
toConsumer :: Monad m => Sink a m b > Consumer a m b Source
Exceptions
catchP :: (MonadBaseControl IO m, Exception e) => Pipe l i o u m r > (e > Pipe l i o u m r) > Pipe l i o u m r Source
See catchC
for more details.
Since 1.0.11
handleP :: (MonadBaseControl IO m, Exception e) => (e > Pipe l i o u m r) > Pipe l i o u m r > Pipe l i o u m r Source
The same as flip catchP
.
Since 1.0.11
tryP :: (MonadBaseControl IO m, Exception e) => Pipe l i o u m r > Pipe l i o u m (Either e r) Source
See tryC
for more details.
Since 1.0.11
catchC :: (MonadBaseControl IO m, Exception e) => ConduitM i o m r > (e > ConduitM i o m r) > ConduitM i o m r Source
Catch all exceptions thrown by the current component of the pipeline.
Note: this will not catch exceptions thrown by other components! For
example, if an exception is thrown in a Source
feeding to a Sink
, and
the Sink
uses catchC
, the exception will not be caught.
Due to this behavior (as well as lack of async exception handling), you
should not try to implement combinators such as onException
in terms of this
primitive function.
Note also that the exception handling will not be applied to any finalizers generated by this conduit.
Since 1.0.11
handleC :: (MonadBaseControl IO m, Exception e) => (e > ConduitM i o m r) > ConduitM i o m r > ConduitM i o m r Source
The same as flip catchC
.
Since 1.0.11
tryC :: (MonadBaseControl IO m, Exception e) => ConduitM i o m r > ConduitM i o m (Either e r) Source
A version of try
for use within a pipeline. See the comments in catchC
for more details.
Since 1.0.11
Utilities
transPipe :: Monad m => (forall a. m a > n a) > Pipe l i o u m r > Pipe l i o u n r Source
Transform the monad that a Pipe
lives in.
Note that the monad transforming function will be run multiple times, resulting in unintuitive behavior in some cases. For a fuller treatment, please see:
https://github.com/snoyberg/conduit/wiki/Dealingwithmonadtransformers
This function is just a synonym for hoist
.
Since 0.4.0
mapOutputMaybe :: Monad m => (o1 > Maybe o2) > Pipe l i o1 u m r > Pipe l i o2 u m r Source
Same as mapOutput
, but use a function that returns Maybe
values.
Since 0.5.0
:: Monad m  
=> (i1 > i2)  map initial input to new input 
> (l2 > Maybe l1)  map new leftovers to initial leftovers 
> Pipe l2 i2 o u m r  
> Pipe l1 i1 o u m r 
Apply a function to all the input values of a Pipe
.
Since 0.5.0
sourceList :: Monad m => [a] > Pipe l i a u m () Source
Convert a list into a source.
Since 0.3.0
withUpstream :: Monad m => Pipe l i o u m r > Pipe l i o u m (u, r) Source
Returns a tuple of the upstream and downstream results. Note that this will force consumption of the entire input stream.
Since 0.5.0
unwrapResumable :: MonadIO m => ResumableSource m o > m (Source m o, m ()) Source
Unwraps a ResumableSource
into a Source
and a finalizer.
A ResumableSource
represents a Source
which has already been run, and
therefore has a finalizer registered. As a result, if we want to turn it
into a regular Source
, we need to ensure that the finalizer will be run
appropriately. By appropriately, I mean:
 If a new finalizer is registered, the old one should not be called.
 If the old one is called, it should not be called again.
This function returns both a Source
and a finalizer which ensures that the
above two conditions hold. Once you call that finalizer, the Source
is
invalidated and cannot be used.
Since 0.5.2
unwrapResumableConduit :: MonadIO m => ResumableConduit i m o > m (Conduit i m o, m ()) Source
Unwraps a ResumableConduit
into a Conduit
and a finalizer.
Since unwrapResumable
for more information.
Since 1.0.17
zipSinks :: Monad m => Sink i m r > Sink i m r' > Sink i m (r, r') Source
Combines two sinks. The new sink will complete when both input sinks have completed.
Any leftovers are discarded.
Since 0.4.1
zipSources :: Monad m => Source m a > Source m b > Source m (a, b) Source
Combines two sources. The new source will stop producing once either source has been exhausted.
Since 1.0.13
zipSourcesApp :: Monad m => Source m (a > b) > Source m a > Source m b Source
Combines two sources. The new source will stop producing once either source has been exhausted.
Since 1.0.13
zipConduitApp :: Monad m => ConduitM i o m (x > y) > ConduitM i o m x > ConduitM i o m y Source
Since 1.0.17
Turn a Sink
into a Conduit
in the following way:
 All input passed to the
Sink
is yielded downstream.  When the
Sink
finishes processing, the result is passed to the provided to the finalizer function.
Note that the Sink
will stop receiving input as soon as the downstream it
is connected to shuts down.
An example usage would be to write the result of a Sink
to some mutable
variable while allowing other processing to continue.
Since 1.1.0