Kevin Wortman scripsit:

> If the "delete x from A" operation invalidates the "for each element x"
> cursor then you're out of luck.

And yet my implementation of sets actually does this!  Oops.  Well, the
implementation needs a massive update anyway.

> Then again, insisting that live cursors stay valid is a heavy
> implementation burden that adds a lot of complexity and effectively
> prohibits some data structures.

Exactly so.

--
John Cowan  xxxxxx@ccil.org  http://ccil.org/~cowan
Female celebrity stalker, on a hot morning in Cairo:
"Imagine, Colonel Lawrence, ninety-two already!"
El Auruns's reply:  "Many happy returns of the day!"