[Help-smalltalk] Re: Continuations and generators

[Paolo Bonzini]

> > I would like to know if there is interest in moving generators (and,
> > as a prerequisite, continuations) to the main image.
>
> I'd be happy with them in kernel as long as this doesn't later lead to
> sacrificing the performance of the engine in general to improve
> performance of the (apparently stack-copying-on-resume) continuation
> support.

Stack copying on resume is done simply with "thisContext deepCopy".

Actually, having them in the kernel does speed up the generator example 
by 15%, but that's because I added a primitive equivalent to this code:

    resume: returnValue nextContinuation: aContext
        | continuation |
        stack isNil ifTrue: [ ^self primitiveFailed ].
        continuation := stack.
        stack := aContext.
        thisContext parentContext: continuation.
        ^returnValue!

... but which does not need to construct a real object for thisContext.


As I anticipated, stack-copying-on-resume is a matter of doing

    continuation resume: value nextContinuation: stack deepCopy

while the more efficient version

    continuation resume: value nextContinuation: nil

only allows a continuation to restart once.

Paolo