[sigc] Why no slot_list::swap()?

["Victor Porton,,," <porton ex-code com>]

Why there are no slot_list::swap() which would swap
two slot_lists's?

It could be useful to temporarily disconnect all slots for
a signal (to block a signal).

Note that I'm not subscribed. My email porton ex-code com 

I'm developing this library (not yet really ready):
http//ex-code.com/propcpp/

I want an efficient (especially concerning memory use)
impl of blocking of signals.