Re: Continuations

[James Knight <jknight@xxxxxxxx>]

On Tuesday, April 16, 2002, at 06:43  PM, Avi Bryant wrote:
> On 16 Apr 2002, Jonathan Bachrach wrote:
> The wiki mentions call/cc as a wish.  Any idea what the realistic
> prospects of this being implemented are?  I'm interested not so much in
> microthreads as in the use of continuations in web apps, which I've come
> to see as essential.

Well - so far, they have not been implemented because GOO uses a 
standard C stack to call functions, and the C setjmp/longjmp to handle 
the "esc" limited continuation construct. There is a clear path on how 
to go forward and remove the dependence on the C stack, but I believe 
doing so in a way that provides reasonable performance requires 
asm-level trickery, which so far noone has felt up to confronting. I'm 
sure the appropriate code could be hacked out of other lisp-runtimes, if 
anyone can find it.

When you say you're not interested in microthreads, you're interested in 
web-app continuations, I presume this means you want continuations that 
can be called multiple times, as well? (to support the back button) Damn 
I was hoping we wouldn't actually need to do that. :)

James