Concurrency support?

Brendan Eich brendan at mozilla.org
Mon Jun 26 06:45:32 PDT 2006


On Jun 26, 2006, at 4:09 AM, Lars T Hansen wrote:

> The point I want to make is that we probably do not want to provide
> full continuations as an abstraction on which to build threads,
> coroutines, generators, exceptions, and so on, but instead to provide
> these other more controllable forms directly instead.

Thanks for the complete example.  I wanted to back up Lars here by  
affirming that we've discussed call/cc in TG1 meetings and come to  
this conclusion, already.  So this is a consensus position, as far as  
I know.

Rhino (http://www.mozilla.org/rhino/) has a call/cc implementation  
from the Apache Cocoon folks, exposed as a Continuation object.   
Chris Double knows this well, including a bug (http://www.google.com/ 
url?sa=t&ct=res&cd=4&url=http%3A%2F%2Fwww.bluishcoder.co.nz%2F2006% 
2F03%2Fjavascript-partial-continuations.html&ei=AuSfRKjACoSo- 
gHd9_jTCQ&sig2=6ADqe10tNY06KRjiGXW46g).

So far, the bugs or limitations combined with the promise of call/cc  
generality seem to me to indicate overkill, or overreach.  If anyone  
on this list has an example use-case of call/cc in JS that you think  
is important, and that can't be mapped to coroutine-generators  
(Python 2.5, PEP 342), please post it.

/be




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