[Haskell-cafe] Cleaning up stable names?

Peter Verswyvelen bugfact at gmail.com
Tue Sep 1 13:02:13 EDT 2009

I was planning to use them for caching OpenGL display lists and render
targets. These are generated from a pure scene graph description, and
if the same description is handed over to the render engine, it would
just reuse the previously cached OpenGL object.  I can of course just
embedding and IORef inside the pure structures, that would also work I

On Tue, Sep 1, 2009 at 6:09 PM, Job Vranish<jvranish at gmail.com> wrote:
> Well usually, when I've used stable names, I've just used them to check if
> things are the same, and then thrown them away. So no chance for a space
> leak. It's usually unsafe to keep stable names around for very long as they
> can lose their ability to tell if two things are the same (if this surprises
> you, you should carefully reread
> http://haskell.org/ghc/docs/latest/html/libraries/base/System-Mem-StableName.html#v%3AmakeStableName
> ).
> Out of curiosity, how are you planning on using them?

> - Job
> On Tue, Sep 1, 2009 at 3:40 AM, Peter Verswyvelen <bugfact at gmail.com> wrote:
>> but without that function, stable names are not that useful I guess? they
>> would cause a space leak?
>> On Mon, Aug 31, 2009 at 10:59 PM, Job Vranish <jvranish at gmail.com> wrote:
>>> I also would like a isStableNameTargetAlive function.
>>> Though if you had such a function then you probably _could_ make a
>>> deRefStableName function, which, since there isn't one, probably means that
>>> such a function would be hard to make.
>>> - Job
>>> On Sun, Aug 30, 2009 at 4:54 PM, Peter Verswyvelen <bugfact at gmail.com>
>>> wrote:
>>>> >From the documentation, I don't think I grasp how stable names work.
>>>> From the docs:
>>>> "There is no deRefStableName operation. You can't get back from a stable
>>>> name to the original Haskell object. The reason for this is that the
>>>> existence of a stable name for an object does not guarantee the existence of
>>>> the object itself; it can still be garbage collected."
>>>> From this I can conclude that stable names behave a bit like weak
>>>> pointers.
>>>> However, suppose I have a hash table of these stable names. How can I
>>>> remove the redundant stable names from the table? I mean removing stable
>>>> names that refer to an object that is garbage collected? I don't see any
>>>> function for checking that (e.g. isStableNameTargetAlive or something)
>>>> Thanks,
>>>> Peter
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