[Haskell-cafe] HANSEI in Haskell?

Antoine Latter aslatter at gmail.com
Thu Feb 24 23:20:46 CET 2011

On Thu, Feb 24, 2011 at 12:57 PM, Chung-chieh Shan
<ccshan at cs.rutgers.edu> wrote:
> Arnaud Clère <arnaud.clere at free.fr> wrote in article <ik64e9$j6a$1 at dough.gmane.org> in gmane.comp.lang.haskell.cafe:
>> On 24/02/2011 09:30, oleg at okmij.org wrote:
>> > The sort of laziness needed for non-deterministic programming calls
>> > for first-class store.  It can be emulated, albeit *imperfectly*,
>>  > for example, as was described in the ICFP09 paper.
>> What do you mean by "imperfectly"?
> I think Oleg meant that, because the garbage collector only understands
> the native store and not our emulation of first-class stores, cells of
> a first-class store that are no longer referenced will nevertheless not
> be garbage-collected until the store itself is garbage-collected.  What
> we need is a way to tell the garbage collector that the store reference
> and the cell reference are both needed to access the data so the data
> can be garbage-collected as soon as *either* the store reference *or
> the cell reference* is.  (Analogy from the capabilities literature:
> the key and the lock are both needed to open the door so the door can
> be garbage-collected as soon as either the key or the lock is.)  Any
> thoughts on how to achieve that?

Here's a weak cell which is a candidate for GC as soon as either the
cell or the key is lost:


The implementation is GHC specific, as far as I know.

I don't know if it's exactly what you're looking for, but the idea
could be adapted towards some other purpose.


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