# 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.Concurrent
import Data.Dynamic
import Control.DeepSeq
import GHC.Stack (HasCallStack)
main :: IO ()
main = defaultMain firstExample
newtype WhoAreYou = WhoAreYou ProcessId
deriving (Typeable, NFData, Show)
firstExample
:: (HasCallStack, Member Logs 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:
```text
DEBUG scheduler loop entered ForkIOScheduler.hs line 157
DEBUG !1 enter process ForkIOScheduler.hs line 549
NOTICE !1 ++++++++ main process started ++++++++ ForkIOScheduler.hs line 461
DEBUG !2 enter process ForkIOScheduler.hs line 549
INFO !2 I am waiting for someone to ask me... Main.hs line 26
INFO !2 !1 just needed to know it. Main.hs line 29
DEBUG !2 exit normally ForkIOScheduler.hs line 568
INFO !1 I just met Alice Main.hs line 34
NOTICE !1 ++++++++ main process returned ++++++++ ForkIOScheduler.hs line 463
DEBUG !1 exit normally ForkIOScheduler.hs line 568
DEBUG scheduler loop returned ForkIOScheduler.hs line 159
DEBUG scheduler cleanup begin ForkIOScheduler.hs line 154
NOTICE cancelling processes: [] ForkIOScheduler.hs line 168
NOTICE all processes cancelled ForkIOScheduler.hs line 179
```
## 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