built-in method
before/3
Description
before(Object, Message, Sender)
User-defined method for handling before events.
This method is declared in the monitoring built-in
protocol as a public predicate and is automatically called by the runtime for
messages sent using the (::)/2 control construct
from within objects compiled with the events flag set
to allow.
Note that you can make this predicate scope protected or private by using,
respectively, protected or private implementation
of the monitoring protocol.
Modes and number of proofs
before(?object_identifier, ?callable, ?object_identifier) - zero_or_more
Errors
(none)
Examples
:- object(...,
implements(monitoring),
...).
% write a log message when a message is sent:
before(Object, Message, Sender) :-
writeq(Object), write('::'), writeq(Message),
write(' from '), writeq(Sender), nl.
See also