# extensible-effects-concurrent
Message passing concurrency with 'forkIO' and 'extensible-effects' inspired by Erlang.
[](https://travis-ci.org/sheyll/extensible-effects-concurrent)
[](http://hackage.haskell.org/package/extensible-effects-concurrent)
Also included:
- Logging
- Memory Leak Free `forever`
## GHC Extensions
In order to use the library you might need to activate some extension
in order to fight some ambiguous types, stemming from the flexibility to
choose different Scheduler implementations.
- AllowAmbiguousTypes
- TypeApplications
## Example
```haskell
module Main where
import Control.Eff
import Control.Eff.Lift
import Control.Eff.Concurrent
import Data.Dynamic
import Control.Concurrent
import Control.DeepSeq
main :: IO ()
main = defaultMain
(do
lift (threadDelay 100000) -- because of async logging
firstExample
lift (threadDelay 100000) -- ... async logging
)
-- The SchedulerProxy paremeter contains the effects of a specific scheduler
-- implementation.
newtype WhoAreYou = WhoAreYou ProcessId deriving (Typeable, NFData, Show)
firstExample
:: (HasLogging IO q) => Eff (InterruptableProcess q) ()
firstExample = do
person <- spawn
(do
logInfo "I am waiting for someone to ask me..."
WhoAreYou replyPid <- receiveMessage
sendMessage replyPid "Alice"
logInfo (show replyPid ++ " just needed to know it.")
)
me <- self
sendMessage person (WhoAreYou me)
personName <- receiveMessage
logInfo ("I just met " ++ personName)
```
**Running** this example causes this output:
(_not entirely true because of async logging, but true enough_)
```text
2018-11-05T10:50:42 DEBUG scheduler loop entered ForkIOScheduler.hs line 131
2018-11-05T10:50:42 DEBUG !1 [ThreadId 11] enter process ForkIOScheduler.hs line 437
2018-11-05T10:50:42 NOTICE !1 [ThreadId 11] ++++++++ main process started ++++++++ ForkIOScheduler.hs line 394
2018-11-05T10:50:42 DEBUG !2 [ThreadId 12] enter process ForkIOScheduler.hs line 437
2018-11-05T10:50:42 INFO !2 [ThreadId 12] I am waiting for someone to ask me... Main.hs line 27
2018-11-05T10:50:42 INFO !2 [ThreadId 12] !1 just needed to know it. Main.hs line 30
2018-11-05T10:50:42 DEBUG !2 [ThreadId 12] returned ForkIOScheduler.hs line 440
2018-11-05T10:50:42 INFO !1 [ThreadId 11] I just met Alice Main.hs line 35
2018-11-05T10:50:42 NOTICE !1 [ThreadId 11] ++++++++ main process returned ++++++++ ForkIOScheduler.hs line 396
2018-11-05T10:50:42 DEBUG !1 [ThreadId 11] returned ForkIOScheduler.hs line 440
2018-11-05T10:50:42 DEBUG scheduler loop returned ForkIOScheduler.hs line 133
2018-11-05T10:50:42 DEBUG scheduler cleanup begin ForkIOScheduler.hs line 137
2018-11-05T10:50:42 NOTICE cancelling processes: [] ForkIOScheduler.hs line 149
2018-11-05T10:50:42 DEBUG scheduler cleanup done ForkIOScheduler.hs line 141
```
## TODO
### Stackage
Still todo...
[](http://stackage.org/lts/package/extensible-effects-concurrent)
### Other
- Process Linking/Monitoring
- Scheduler `ekg` Monitoring
- Timers and Timeouts (e.g. in `receive`)
- Rename stuff