On Tue, Feb 24, 2009 at 08:04:33PM +0300, Daneel Yaitskov wrote:
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
Hi Daneel, Note that record syntax like
data TestB = TestB { xGetB :: MVar Bool }
only adds capabilities; you can still use TestB as if it was defined without record syntax, like TestA. So you are not required to use the TestB {xGetB = tmp} syntax to create a TestB, you could also just say 'TestB tmp'. So the second code example should work fine if you just replace all the 'A's with 'B's. Does this answer your question? I must admit that I am not entirely sure what you are asking, so if this doesn't address your question feel free to clarify. -Brent