[e-lang] multiway when-catch

[Kevin Reid]

On Oct 29, 2007, at 14:16, Rob Withers wrote:
> I've revived my work on SqueakElib and I am trying to implement the  
> multiway when-catch.  I have #whenResolved: and #whenBroken:  
> defined and that is how I specify a when-catch; when-catch is not  
> part of the language I use.  I suppose my first question is: is  
> when-catch defined in terms of #whenResolved: and #whenBroken:?

Yes.

> If so, what does it look like?

You can ask the implementation: just do interp.setExpand(true) then  
enter the code you want to see the expansion of, or write it inside  
of an e`...` quasiquote.

Most expansions use objects from the safe scope; look in jsrc/org/ 
erights/e/elang/scope/ScopeSetup.java to see what the bindings are.

> ... where #getFork returns an eventualRef and the #% message  
> concatenates promises to create a promiseSet.  Unfortunately,  
> nothing holds onto the promiseSet so it is getting GCed.  I suspect  
> that I need to pass the promiseSet as an argument to #whenResolved:  
> msgs sent to each promise, but I am not sure how.

I think your promiseSet corresponds to the components produced by  
promiseAllFulfilled, which multiway-when uses, as you will see in the  
expansion. I recommend that you simply compile/translate  
promiseAllFulfilled.emaker to your platform, as it is entirely non- 
primitive and well-designed.

Particularly, there should not be any weak references involved, so GC  
is irrelevant.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>