[Haskell-beginners] data constructor with IO type
Daneel Yaitskov
rtfm.rtfm.rtfm at gmail.com
Tue Feb 24 12:04:33 EST 2009
Hi All,
I'd like to know does it exist a method which allow to construct the TestB
type without a temporary variable such as the TestA constructor.
---
module Main where
import Monad
import Control.Concurrent
data TestA = TestA (MVar Bool)
xGetA (TestA x) = x
data TestB = TestB { xGetB :: MVar Bool }
---
main =
do tmp <- newMVar False
let t = TestB { xGetB = tmp } in
do vt <- takeMVar t
putStrLn ("HELLO" ++ show vt)
---
main = do
t <- liftM TestA (newMVar False)
vt <- takeMVar (xGetA t)
putStrLn ("HELLO" ++ show vt)
---
Daneel Yaitskov
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