This module contains all the central monads in the CHP library.
- data CHP a
- class MonadIO m => MonadCHP m where
- runCHP :: CHP a -> IO (Maybe a)
- runCHP_ :: CHP a -> IO ()
- embedCHP :: CHP a -> CHP (IO (Maybe a))
- embedCHP_ :: CHP a -> CHP (IO ())
- embedCHP1 :: (a -> CHP b) -> CHP (a -> IO (Maybe b))
- embedCHP1_ :: (a -> CHP b) -> CHP (a -> IO ())
- onPoisonTrap :: CHP a -> CHP a -> CHP a
- onPoisonRethrow :: CHP a -> CHP () -> CHP a
- throwPoison :: CHP a
- class Poisonable c where
- poisonAll :: (Poisonable c, MonadCHP m) => [c] -> m ()
- skip :: CHP ()
- stop :: CHP a
- waitFor :: Int -> CHP ()
The central monad of the library. You can use
Control.Concurrent.CHP.Monad.runCHP_ to execute programs in this
Runs a CHP program. You should use this once, at the top-level of your program. Do not ever use this function twice in parallel and attempt to communicate between those processes using channels. Instead, run this function once and use it to spawn off the parallel processes that you need.
Allows embedding of the CHP monad back into the IO monad. The argument that this function takes is a CHP action (with arbitrary behaviour). The function is monadic, and returns something of type: IO a. This is an IO action that you can now use in the IO monad wherever you like. What it returns is the result of your original action.
This function is intended for use wherever you need to supply an IO callback (for example with the OpenGL libraries) that needs to perform CHP communications. It is the safe way to do things, rather than using runCHP twice (and also works with CSP and VCR traces -- but not structural traces!).
A helper like embedCHP for callbacks that take an argument
A convenient version of embedCHP1 that ignores the result
Allows you to provide a handler for sections with poison. It is usually used in an infix form as follows:
(readChannel c >>= writeChannel d) `onPoisonTrap` (poison c >> poison d)
It handles the poison and does not rethrow it (unless your handler
does so). If you want to rethrow (and actually, you'll find you usually
onPoisonTrap, this function allows you to provide a handler
for poison. The difference with this function is that even if the
poison handler does not throw, the poison exception will always be
re-thrown after the handler anyway. That is, the following lines of
code all have identical behaviour:
foo foo `onPoisonRethrow` throwPoison foo `onPoisonRethrow` return ()
A class indicating that something is poisonable.
Poisons the given item.
Checks if the given item is poisoned. If it is, a poison exception will be thrown.
Added in version 1.0.2.
Poisons all the given items. A handy shortcut for
The classic skip process/guard. Does nothing, and is always ready.
Suitable for use in an
The stop guard. Its main use is that it is never ready in a choice, so
can be used to mask out guards. If you actually execute
stop, that process
will do nothing more. Any parent process waiting for it to complete will
The type of this function was generalised in CHP 1.6.0.
Waits for the specified number of microseconds (millionths of a second). There is no guaranteed precision, but the wait will never complete in less time than the parameter given.
Suitable for use in an
Control.Concurrent.CHP.Alt.alt, but note that
waitFor 0 is not the same
Control.Concurrent.CHP.Alt.</> x will not always select the first guard,
depending on x. Included in this is the lack of guarantee that
waitFor n will select the first guard for any value
of n (including 0). It is not useful to use two
waitFor guards in a
NOTE: If you wish to use this as part of a choice, you must use
as a GHC compilation option (at least under 6.8.2).