observable-sharing-0.1.0.0: src/Data/Ref.hs

module Data.Ref where

import Data.Unique
import System.IO.Unsafe
import Control.Applicative

--------------------------------------------------------------------------------
-- * References
--------------------------------------------------------------------------------

data Ref a = Ref { refNr :: Unique , deref :: a }

instance Eq (Ref a) where
  Ref u1 _ == Ref u2 _ = u1 == u2

instance Show a => Show (Ref a) where
  show (Ref u x) = "(Ref " ++ show (hashUnique u) ++ " " ++ show x ++ ")"

ref :: a -> Ref a
ref x = unsafePerformIO $ flip Ref x <$> newUnique
{-# NOINLINE ref #-}

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-- the end.