Use strict variant of atomicModifyIORef in System.Metric.Label.modify

Author: arybczak

System/Metrics/Label.hs

@@ -12,7 +12,7 @@ module System.Metrics.Label
     , modify
     ) where
 
-import Data.IORef (IORef, atomicModifyIORef, atomicWriteIORef, newIORef, readIORef)
+import Data.IORef (IORef, atomicModifyIORef', atomicWriteIORef, newIORef, readIORef)
 import qualified Data.Text as T
 import Prelude hiding (read)
 
@@ -34,6 +34,4 @@ set (C ref) !i = atomicWriteIORef ref i
 -- | Set the label to the result of applying the given function to the
 -- value.
 modify :: (T.Text -> T.Text) -> Label -> IO ()
-modify f (C ref) = do
-    !_ <- atomicModifyIORef ref $ \ i -> let i' = f i in (i', i')
-    return ()
+modify f (C ref) = atomicModifyIORef' ref $ \i -> (f i, ())