How to write this iterator?

[Paul Rubin]

Paul Rubin <http://phr.cx@NOSPAM.invalid> writes:
> Hmm, here's an approach using the .throw() operation from PEP 342.
> It's obviously untested, since that feature is not currently part of
> Python, probably incorrect, and maybe just insane.

Pardon the unintentional "shift/reduce conflict" above.  I mean that
the code sample I posted is probably incorrect and maybe insane, not
that the proposed throw() feature is incorrect or insane.