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Given the handle with which an event is associated, retrieve the event goal.
- An event handle
- A free variable or goal to unify
This built-in predicate is obsolete!
The goal associated with an event handle, created using event_create / 3, is
retrieved using this predicate.
Like event creation, retrieval of the goal produces a copy of the
goal. As a result, if the goal contains variables, they lose their identity
and are replaced with fresh ones.
If the event was disabled, the goal 'true' is retrieved instead of the
Modes and Determinism
- event_retrieve(+, -) is det
- (4) instantiation fault
- EventHandle is un-instantiated
- (5) type error
- EventHandle is not a handle
?- event_create(writeln('Hello world!'), , Event), event_retrieve(Event, EventGoal).
Event = 'EVENT'(16'50421bd0)
EventGoal = writeln('Hello world!')
Yes (0.00s cpu)
event_retrieve / 3