I'm happy to announce the release of my library 'simple-actors', a
DSL-style library for more structured concurrent programs based on the
Actor Model. It offers an alternative to ad-hoc use of Chans that
allows for tight control of side-effects and message passing, and is
especially suited to applications such as simulations of
communicating processes.
You can try it with a
$ cabal install simple-actors
and view the documentation here:
http://hackage.haskell.org/package/simple-actors
or check out the repo here:
https://github.com/jberryman/simple-actors
Here is an example of a system of actors working as a binary tree,
supporting insert and query operations:
---- EXAMPLE ----
module Main
where
import Control.Concurrent.Actors
import Control.Applicative
import Control.Concurrent.MVar
type Node = Mailbox Operation
-- operations supported by the network:
data Operation = Insert { val :: Int }
| Query { val :: Int
, sigVar :: MVar Bool }
-- the actor equivalent of a Nil leaf node:
nil :: Behavior Operation
nil = Receive $ do
(Query _ var) <- received
send var False -- signal that Int is not present in tree
return nil -- await next message
<|> do -- else, Insert received
l <- spawn nil -- spawn child nodes
r <- spawn nil
branch l r . val <$> received -- create branch from inserted val
-- a "branch" node with an Int value 'v' and two children
branch :: Node -> Node -> Int -> Behavior Operation
branch l r v = loop where
loop = Receive $ do
m <- received
case compare (val m) v of
LT -> send l m
GT -> send r m
EQ -> case m of -- signal Int present in tree:
(Query _ var) -> send var True
_ -> return ()
return loop
insert :: Node -> Int -> IO ()
insert t = send t . Insert
-- MVar is in the 'SplitChan' class so actors can 'send' to it:
query :: Node -> Int -> IO Bool
query t a = do
v <- newEmptyMVar
send t (Query a v)
takeMVar v
main = do
t <- spawn nil
mapM_ (insert t) [5,3,7,2,4,6,8]
mapM (query t) [1,5,0,7] >>= print
---- END EXAMPLE ----
I need to do some work on the documentation and performance testing.
If anyone has anyone questions or comments, I would love to hear them.
Thanks,
Brandon
http://coder.bsimmons.name
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