Re: References in XPath that can be represented by a string andstill can be garbage collected

> 
> I've read an article
> http://www.fgeorges.org/exslt2-wiki/References_in_XPath_that_c
an_be_represented_by_a_string_and_still_can_be_garbage_collected.
> It seems to me that the idea of explicit "Resource Manager" 
> object goes against the spirit of functional programming.
> 
> Except that I think it has technical flaws.
> Processor has a great freedom to reorder operations.
> This potentially may lead to dereferencing something that was 
> not referenced.
> 
> I think the better way to is to introduce a map in exslt 2, 
> and then build (unique-string, object) map to store the binding.
> What do you think?

I think there are some ideas worth pursuing here, but I'm not 100% convinced
they are sound.

The concept of a "resource manager" does have the merit that it provides a
scope for the persistence of string references: they are valid so long as
the resource manager exists, and when the resource manager ceases to exist,
the string references are no longer dereferenceable and the nodes can be
garbage collected.

The question marks arise because the resource manager is stateful:
references are added to it incrementally. Therefore, in pathological cases,
the result of

(get-reference($rm, $node), dereference($rm, 'd0'))

will depend on the order of evaluation. However, I'm not sure how much this
matters, since it seems it can only affect the outcome if you try to
dereference a string that didn't originally come from the resource manager,
and the effect of doing that is always going to be unpredictable anyway.

Michael Kay