[racket-dev] request: replace-evt

Hi,

I would like to humbly request a new `replace-evt` procedure that would
work as `wrap-evt` except that when it produces another `evt?`, `sync`
replaces the old event with the newly produced one and restarts.

It will be a good replacement for threads and channels when filtering
events or addition of bookkeeping handlers is desired.

I peeked at the syncing code and it seems doable, but the code is too
dense for me to grok it. :-(

What do you think?

Best regards,
Jan Dvorak