-- Copyright (c) 2009-2010, ERICSSON AB, Koen Claessen
-- All rights reserved.
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{-# OPTIONS_GHC -O0 #-}

-- |
-- A simple implementation of \"observable sharing\". See
--
-- * Koen Claessen, David Sands,
-- \"/Observable sharing for functional circuit description/\",
-- Asian Computing Science Conference, 1999.
--
-- for more details.

module Feldspar.Core.Ref
  ( Ref
  , refId
  , deref
  , ref
  ) where



import Data.Unique
import System.IO.Unsafe



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

instance Eq (Ref a) where
  Ref x _ == Ref y _ = x == y

instance Ord (Ref a) where
  Ref x _ `compare` Ref y _ = x `compare` y



ref :: a -> Ref a
ref x = unsafePerformIO $ do
     u <- newUnique
     return (Ref u x)