26 Nov
2008
26 Nov
'08
5:17 p.m.
On Wed, 2008-11-26 at 13:25 -0800, Ryan Ingram wrote:
In fact:
import Control.Concurrent.STM import Control.Concurrent.STM.TMVar
-- gets a value from one of a list of TMVars takeTMVars :: [TMVar a] -> STM (TMVar a, a) takeTMVars = foldr fetch retry where fetch v act = (takeTMVar v >>= \a -> return (v, a)) `orElse` act
-- puts the given value into exactly one of a list of TMVars putTMVars :: [TMVar a] -> a -> STM (TMVar a) putTMVars vs a = foldr put retry vs where put v act = (putTMVar v a >> return v) `orElse` act
Of course those are TMVars, using STM. So in STM it is easy, whereas with MVars it is a bit harder. Duncan