Felipe Lessa schrieb:
On Mon, Dec 21, 2009 at 12:39:06AM +0100, Daniel Fischer wrote:
Am Sonntag 20 Dezember 2009 23:25:02 schrieb Jamie Morgenstern:
Also, I was wondering if something akin to a "parallel or" exists. By this,
I mean I am looking for a function which, given x : a , y : a, returns
either, whichever computation returns first.
This wouldn't be easy to reconcile with referential transparency.
You can do that in IO, roughly
m <- newEmptyMVar
t1 <- forkIO $ method1 >>= putMVar m
t2 <- forkIO $ method2 >>= putMVar m
rs <- takeMVar m
killThread t1
killThread t2
return rs
But in pure code, I think not.
There's 'unamb' in Hackage, however I think you should carefully
understand its implementation details before using it.
Hello Jamie,
you might want to have a look at the implementation of `race` in the
Conal's 'unamb' package:
http://hackage.haskell.org/packages/archive/unamb/0.2.2/doc/html/src/Data-Unamb.html#race
As your left and right branch do not neccessarily have the same result,
you have to stay in the IO monad.
The function provided by that package is:
> amb :: a -> a -> IO a
Not that I use it myself.
Neither do I, btw.
benedikt
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