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

[Thomas DuBuisson]

zaxis <z_axis at 163.com> wrote:
>> let aaa = unsafePerformIO  $ newIORef []
>> writeIORef aaa [1,2,3]
>> readIORef aaa
> [(),(),()]

What in Haskells name do you think you're doing?  Don't use
unsafePerformIO like that!  Its unnecessary and a bit concerning,
really.

Prelude> :m Data.IORef
Prelude Data.IORef> x <- newIORef [] :: IO (IORef [Int])
Prelude Data.IORef> writeIORef x [1,2,3]
Prelude Data.IORef> readIORef x
[1,2,3]


>
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