[Haskell-cafe] number of references to a variable
andrewcoppin at btinternet.com
Sat Nov 1 13:56:03 EDT 2008
Jan-Willem Maessen wrote:
> On Nov 1, 2008, at 9:38 AM, Andrew Coppin wrote:
>> Alberto G. Corona wrote:
>>> Is there a way to know the number of memory references for a
>>> variable?. The runtime must know it but i do not know if this
>>> available for the program trough any low level trick
>> More precisely, the GC computes it each time it runs. (And only
>> computes it precisely during a "major" pass, not the more frequent
>> "minor" passes.)
> Even this isn't quite true for most GC algorithms. The GC only needs
> to compute whether there is 0 or >= 1 reference to a given location.
> If you can see it, the answer is always >=1, so this information is
> much less useful than you might think!
> Usually the clever thing you want to know is "this is the sole
> reference to the pointed-to object".
Does GHC have weak references? (I seem to recall it does...)
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