let se = new signal_engine esys: The engine
se remains in
`Working 0 until the method
se # signal x is called. At this point
e transitions to
x. Any further call of
signal does not
have any effect.
se is aborted,
signal does not have any effect.
signal may be called from a different thread.
The signalling event is forwarded to the thread running the
method signal :
'a final_state -> unit