dejafu

Concurrency is nice, deadlocks and race conditions not so much. The Par monad family, as defined in abstract-par provides deterministic parallelism, but sometimes we can tolerate a bit of nondeterminism.

This package provides a class of monads for potentially nondeterministic concurrency, with an interface very much in the spirit of Par, but slightly more relaxed. Specifically, MonadConc's IVar equivalent, CVars, can be written to multiple times.

The documentation of the latest developmental version is available online.

MonadConc and IO

The intention of the MonadConc class is to provide concurrency where any apparent nondeterminism arises purely from the scheduling behaviour. To put it another way, a given computation, parametrised with a fixed set of scheduling decisions, is deterministic. This assumption is used by the testing functionality provided by Control.Monad.Conc.SCT.

Whilst this assumption may not hold in general when IO is involved, you should strive to produce test cases where it does.

Contributing

Bug reports, pull requests, and comments are very welcome!

Feel free to contact me on GitHub, through IRC (#haskell on freenode), or email (mike@barrucadu.co.uk).