28 lines
806 B
Haskell
28 lines
806 B
Haskell
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{-# LANGUAGE BangPatterns #-}
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-- | This module defines a type for mutable, string-valued labels.
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-- Labels are variable values and can be used to track e.g. the
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-- command line arguments or other free-form values. All operations on
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-- labels are thread-safe.
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module System.Remote.Label
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(
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Label
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, set
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, modify
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) where
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import Data.IORef (atomicModifyIORef)
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import qualified Data.Text as T
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import System.Remote.Label.Internal
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-- | Set the label to the given value.
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set :: Label -> T.Text -> IO ()
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set (C ref) !i = atomicModifyIORef ref $ \ _ -> (i, ())
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-- | Set the label to the result of applying the given function to the
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-- value.
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modify :: (T.Text -> T.Text) -> Label -> IO ()
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modify f (C ref) = do
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!_ <- atomicModifyIORef ref $ \ i -> let i' = f i in (i', i')
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return ()
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