[Squeak-e] adding eventual sending to Croquet's ScriptProcess and ScriptScheduler

Withers, Robert rwithers at quallaby.com
Fri Feb 14 12:30:09 CET 2003

Andreas, I said:

> -----Original Message-----
> From: Withers, Robert [mailto:rwithers at quallaby.com]

> I am curious about your use the ivar #myQueue in the ScriptProcess.  I
> really like that your ScriptProcess will compute a value, and 
> that that
> value is the 'result' of the process.  That's a very standard view of
> computations.  Isn't it a functional view?  A better approach 
> for supporting
> eventual sending may be to have a subclass of ScriptProcess 
> which holds the
> continuation to the invocation site.

Actually, I am now thinking that a subclass may not be needed, since
ScriptProcess already holds onto the invoking message
(AsyncScriptMessageSend to be replaced by EventualScriptMessageSend for
eventual sending) and the owner, which is the same object.  There are also
the ivars #myHandler and #myEventMap.

In the following method, called when the Process returns from the last stack
frame, there are three different mechanisms that we could hook into to
activate the resolver.

ScriptProcess>>#stopScriptProcess: result 
	owner ifNotNil:[owner scriptStopped: self].
	myHandler ifNotNil:[myHandler releaseTo: nil].
	myEventMap ifNotNil:[self signal: #done with: resultObj].

- owner is the ScriptMessageSend, so an implementation of #scriptStopped: in
the EventualScriptMessageSend, could activate the resolver.  

- myHandler is set when sending #observe: and it is an EventObserver.
Currently this only looks to be used by the #waitUntil protocols and it
blocks on a semaphore.  I suppose that a special observer could be created
that holds the resolver.

- myEventMap holds event registrations.  These can be set at a low-level
with #on:notify: or at a higher level by startScript:when:.  So after the
EventualScriptMessageSend is converted to a ScriptProcess, a registration of
the following could wake up the resolver
	proc on: #done notify: (#resolve: asAsyncScriptMessageIn: self
resolver arguments: #())

What do you think would be the best way to activate the resolver?  


More information about the Squeak-e mailing list