2009/1/26 Alberto G. Corona
Sometimes the StableName library gives different values for the samr function:
First, unsafePerformIO is not subject to referential transparency. You have to ensure it yourself. That's why it's unsafe. Now, did you read the StableName documentation? From the docs: Stable names have the following property: if sn1 :: StableName and sn2 ::
StableName and sn1 == sn2 then sn1 and sn2 were created by calls to makeStableName on the same object. The reverse is not necessarily true: if two stable names are not equal, then the objects they name may still be equal.
So the behavior you cite is perfectly reasonable: does not break referential transparency (unsafePerformIO is the culprit here), and is consistent with the documentation. Luke Sometines gives two alternate values. I checked it in ghc-6.10.1 under
windows and in ghc-6.8.2 under Linux:
This is an example
Prelude> System.Mem.StableName.hashStableName.System.IO.Unsafe.unsafePerformIO $ System.Mem.StableName.makeStableName (*) 15 Prelude> System.Mem.StableName.hashStableName.System.IO.Unsafe.unsafePerformIO $ System.Mem.StableName.makeStableName (*) 14 Prelude> System.Mem.StableName.hashStableName.System.IO.Unsafe.unsafePerformIO $ System.Mem.StableName.makeStableName (*) 15 Prelude> System.Mem.StableName.hashStableName.System.IO.Unsafe.unsafePerformIO $ System.Mem.StableName.makeStableName (*) 14
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