observable-sharing-0.2.0.0: src/Data/Ref.hs

module Data.Ref where

import System.Mem.StableName
import System.IO.Unsafe
import Control.Applicative

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

data Ref a = Ref { label :: StableName a, deref :: a }

instance Eq (Ref a) where
  Ref s1 _ == Ref s2 _ = s1 == s2

instance Show a => Show (Ref a) where
  show (Ref s x) = "(Ref " ++ show (hashStableName s) ++ " " ++ show x ++ ")"

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

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-- the end.