On Wed, Sep 19, 2012 at 8:00 PM, <sdiy...@sjtu.edu.cn> wrote:
> So how do I force IO actions whose results are discarded (including IO ()) to
> be strict?
In your particular case it looks like you want
Data.IORef.modifyIORef'. If your version of GHC doesn't include it you
can write it like so:
-- |Strict version of 'modifyIORef'
modifyIORef' :: IORef a -> (a -> a) -> IO ()
modifyIORef' ref f = do
x <- readIORef ref
let x' = f x
x' `seq` writeIORef ref x'
-- Johan
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