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module SharedString (shareString) where
import Data.HashTable as H
import System.IO.Unsafe (unsafePerformIO)
{-# NOINLINE stringPool #-}
stringPool :: HashTable String String
stringPool = unsafePerformIO $ new (==) hashString
{-# NOINLINE shareString #-}
shareString :: String -> String
shareString s = unsafePerformIO $ do
mv <- H.lookup stringPool s
case mv of
Just s' -> return s'
Nothing -> do
H.insert stringPool s s
return s
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