Revert a CAF?

[John Meacham]

Can you use a weak pointer to do what you want?
If you keep a weak pointer to the head of your expensive list then
itwill be reclaimed at the next major GC I believe. I have used
weakpointers for vaugely similar purposes before.
I guess a downside is that they will always be reclaimed on GC even
ifthere isn't memory pressure, I think.

   John
(resent, accidentally sent to wrong address first)