libraries/compact/tests/compact_mutable.hs


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import Control.Concurrent
import Control.DeepSeq
import Control.Exception
import Data.Compact

data HiddenMVar = HiddenMVar (MVar ())

instance NFData HiddenMVar where
  rnf x = x `seq` () -- ignore the function inside

main = do
  m <- newEmptyMVar
  compact (HiddenMVar m)