[Haskell-cafe] why cannot i get the value of a IORef variable ?

[zaxis]

Yes, it works now!  thank you very much!


Kyle Murphy-2 wrote:
> 
> 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 at 163.com> wrote:
> 
>>
>> > let aaa = unsafePerformIO  $ newIORef []
>> > writeIORef aaa [1,2,3]
>> > readIORef aaa
>> [(),(),()]
>>
>> sincerely!
>> --
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>>
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