Generic broadcasting service. Broadcasts are made using the predicate broadcast(+Templ). All registered `listeners' will have their goal called. Success or failure of this is ignored. The listener can not bind arguments.

This library is particularly useful for disconnecting modules in an application. Modules can broadcast events such as changes, anticipating other modules need to react on such changes. For example, settings.pl broadcasts changes to settings, allowing dependent modules to react on changes:

:- listen(setting(changed(http:workers, New)),
          change_workers(New)).

change_workers(New) :-
        setting(http:port, Port),
        http_workers(Port, New).

 listen(+Listener, +Templ, :Goal) is det

 listen(+Templ, :Goal) is det

Open a channel for listening for events of the given `Templ'.

 unlisten(+Listener) is det

 unlisten(+Listener, +Templ) is det

 unlisten(+Listener, +Templ, :Goal) is det

Destroy a channel. All arguments may be variables, removing the all matching listening channels.

 listening(?Listener, ?Templ, ?Goal) is nondet

returns currently open channels

 broadcast(+Templ) is det

Broadcast given event.

 broadcast_request(+Templ) is nondet

Broadcast given event till accepted. Succeeds then, fail if no listener accepts the call. Bindings made by the listener goal are maintained. May be used to make broadcast requests.