Safe Haskell | Safe-Inferred |
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Control.Concurrent.CHP.Channels.Communication
Description
All the channel-ends in CHP are instances of ReadableChannel
(for ends that
you can read from) or WriteableChannel
(for ends that you can write to).
The readChannel
and writeChannel
functions are the standard way to communicate
on a channel. These functions wait for the other party in the communication
to arrive, then exchange the data, then complete. In pseudo-code, the semantics
are like this when two parties (shown here as two columns) communicate:
do sync sync x <- return y done done
Further options are offered by the extReadChannel
and extWriteChannel
channels,
which allow either side to perform additional (so-called extended) actions during the communication.
The semantics when both sides are performing extended actions are:
do sync sync y <- extWriteAction x <- return y x' <- extReadAction x done done done return x'
Neither end need know that the other is performing an extended action, and any
combination is possible (e.g. a normal writeChannel
with an extReadChannel
).
- class ReadableChannel chanEnd where
- readChannel :: chanEnd a -> CHP a
- extReadChannel :: chanEnd a -> (a -> CHP b) -> CHP b
- class WriteableChannel chanEnd where
- writeChannel :: chanEnd a -> a -> CHP ()
- extWriteChannel :: chanEnd a -> CHP a -> CHP ()
- extWriteChannel' :: chanEnd a -> CHP (a, b) -> CHP b
- writeValue :: WriteableChannel chanEnd => a -> chanEnd a -> CHP ()
- writeChannelStrict :: (NFData a, WriteableChannel chanEnd) => chanEnd a -> a -> CHP ()
Documentation
class ReadableChannel chanEnd whereSource
A class indicating that a channel can be read from.
Methods
readChannel :: chanEnd a -> CHP aSource
Reads from the given reading channel-end
extReadChannel :: chanEnd a -> (a -> CHP b) -> CHP bSource
Performs an extended read from the channel, performing the given action before freeing the writer
class WriteableChannel chanEnd whereSource
A class indicating that a channel can be written to.
Methods
writeChannel :: chanEnd a -> a -> CHP ()Source
Writes from the given writing channel-end
extWriteChannel :: chanEnd a -> CHP a -> CHP ()Source
Starts the communication, then performs the given extended action, then sends the result of that down the channel.
extWriteChannel' :: chanEnd a -> CHP (a, b) -> CHP bSource
Like extWriteChannel, but allows a value to be returned from the inner action.
This function was added in version 1.4.0.
writeValue :: WriteableChannel chanEnd => a -> chanEnd a -> CHP ()Source
A useful synonym for flip writeChannel
. Especially useful with claim
so that instead of writing claim output (flip writeChannel 6)
you can write
claim output (writeValue 6)
.
Added in version 1.5.0.
writeChannelStrict :: (NFData a, WriteableChannel chanEnd) => chanEnd a -> a -> CHP ()Source
A helper function that uses the parallel strategies library (see the paper: "Algorithm + Strategy = Parallelism", P.W. Trinder et al, JFP 8(1) 1998, http://www.macs.hw.ac.uk/~dsg/gph/papers/html/Strategies/strategies.html) to make sure that the value sent down a channel is strictly evaluated by the sender before transmission.
This is useful when you want to write worker processes that evaluate data and send it back to some "harvester" process. By default the values sent back may be unevaluated, and thus the harvester might end up doing the evaluation. If you use this function, the value is guaranteed to be completely evaluated before sending.
Added in version 1.0.2.