Dan Sugalski <[EMAIL PROTECTED]> wrote: > At 10:38 PM +0100 3/18/04, Leopold Toetsch wrote: >> >>Which brings up again my warnocked question: How can return >>continuations get reused?
> Works like this. (No pasm, but it should be obvious) Ok. First (and that applies to Jens example too), I'd like to outline continuation vs return continuation and its usage: 1) First there was only a Continuation PMC. Performance with CPS sucked. So I did invent a RetContinuation PMC Performance sucked less. The difference between these two is: the former has COW copied stacks inside its context, the latter has only pointers of the stacks in its context. 2) A return continuation is automatically created by invokecc callmethodcc It's totally hidden when using PIR function or method call syntax _func(a, b) obj."meth"(args) These internally create above opcodes and create a new return continuation on each sub or method invocation 3) Returning from the sub or method in PIR syntax again totally hides the return continuation .pcc_begin_return .return result .pcc_end_return .end or just .sub _foo .end # automatic return sequence inserted. 4) From PIR level there is no official way to even reference this return continuation - its invisible. 5) *But* > If a continuation's taken from within a sub somewhere, return > continuations may (probably will) be used multiple times, once for > the original return then once for each time the continuation is > invoked. 6) Yes, that's true. So the questios is: Can we invent some HLL PIR syntax that clearly indicates: this subroutine will return multiple times through the same return continuation. We have already a similar construct for Coroutines: .pcc_begin_yield .result # optional .pcc_end_yield This is invokeing the coroutine and returns to the caller. What's the usage of Continuations from HLLs point of view? Can we get some hints, what is intended? I'd like to have, if possible a clear indication: that's a plain function or method call and this is not. I think the possible speedup is worth the effort. leo
