I assume you're trying this at the GHCi prompt, which is where you're problem is coming from, specifically on the first line.
When you do:
> let aaa = unsafePerformIO $ newIORef []
GHCi takes a wild stab at the type of [] and comes up with the type [()], so now you have a IORef [()] type, which is why when you try
to store [1,2,3] in the IORef you get back [(),(),()]. Try this instead and it should work:
> let aaa = unsafePerformIO $ newIORef ([] :: [Int])

-R. Kyle Murphy
--
Curiosity was framed, Ignorance killed the cat.


On Thu, Oct 22, 2009 at 01:02, zaxis <z_axis@163.com> wrote:

> let aaa = unsafePerformIO  $ newIORef []
> writeIORef aaa [1,2,3]
> readIORef aaa
[(),(),()]

sincerely!
--
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