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68 lines
2.6 KiB
Markdown
Executable File
68 lines
2.6 KiB
Markdown
Executable File
concurrency
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===========
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A typeclass abstraction over much of Control.Concurrent (and some
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extras!). If you're looking for a general introduction to Haskell
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concurrency, you should check out the excellent
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[Parallel and Concurrent Programming in Haskell][parconc], by Simon
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Marlow. If you are already familiar with concurrent Haskell, just
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change all the imports from Control.Concurrent.* to
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Control.Concurrent.Classy.* and fix the type errors.
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A brief list of supported functionality:
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- Threads: the `forkIO*` and `forkOn*` functions, although bound
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threads are not supported.
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- Getting and setting capablities.
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- Yielding and delaying.
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- Mutable state: STM, `MVar`, and `IORef`.
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- Atomic compare-and-swap for `IORef`.
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- Exceptions.
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- All of the data structures in Control.Concurrent.* and
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Control.Concurrent.STM.* have typeclass-abstracted equivalents.
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- A reimplementation of the [async][] package, providing a
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higher-level interface over threads, allowing users to conveniently
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run `MonadConc` operations asynchronously and wait for their
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results.
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This is quite a rich set of functionality, although it is not
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complete. If there is something else you need, file an issue!
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This used to be part of dejafu, but with the dejafu-0.4.0.0 release,
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it was split out into its own package.
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The documentation of the latest developmental version is
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[available online][docs].
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Why this and not something else?
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--------------------------------
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- **Why not base:** like lifted-base, concurrency uses typeclasses to
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make function types more generic. This automatically eliminates
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calls to `lift` in many cases, resulting in clearer and simpler
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code.
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- **Why not lifted-base:** fundamentally, lifted-base is still using
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actual threads and actual mutable variables. When using a
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concurrency-specific typeclass, this isn't necessarily the case. The
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dejafu library provides non-IO-based implementations to allow
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testing concurrent programs.
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- **Why not IOSpec:** IOSpec provides many of the operations this
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library does, however it uses a free monad to do so, which has extra
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allocation overhead. Furthermore, it does not expose enough of the
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internals in order to accurately test real-execution semantics, such
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as relaxed memory.
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Contributing
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------------
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Bug reports, pull requests, and comments are very welcome!
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Feel free to contact me on GitHub, through IRC (#haskell on freenode),
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or email (mike@barrucadu.co.uk).
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[docs]: https://docs.barrucadu.co.uk/concurrency/dejafu-0.4
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[async]: https://hackage.haskell.org/package/async
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[parconc]: http://chimera.labs.oreilly.com/books/1230000000929
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