[ Obsolete | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# event_create(+Goal, -EventHandle)

Create an ECLiPSe event from an arbitrary goal.

Goal
  An arbitrary goal
EventHandle
  A free variable

### This built-in predicate is obsolete!

## Description

This creates an event from the goal provided, which can be raised with the standard event handling predicates (e.g. event / 1, event_after / 2 and event_after_every / 2) using the associated handle.

The event creation requires non-logical copying of the goal. As a result, if the goal contains variables, they lose their identity and are replaced with fresh ones.

The intended use of such events are for localised event handling or when it is necessary to pass ground parameters to the event goal, i.e. when the use of a global event handler is unnecessary or does not suffice.

It should be noted that the event handle is the only way to uniquely identify a given event. E.g. if an event has been scheduled as an after-event (using event_after/3 or events_after/2), it can only be cancelled by invoking cancel_after_event/2 with the correct handle.

### Modes and Determinism

- event_create(+, -) is det

### Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

### Exceptions

(4) instantiation fault
  Goal is not instantiated
(5) type error
  Goal is not a valid goal
(5) type error
  EventHandle is not a free variable

## Examples

        ?- event_create(writeln('Goodbye cruel world!'), Event),
        	writeln('Hello world!'),
    	event(Event).
        Hello world!
        Goodbye cruel world!
        Event = 'EVENT'(16'503f0238)
        Yes (0.00s cpu)

        ?- event_create(writeln('e1'), E1Event),
    	event_create(writeln('e2'), E2Event),
    	events_after([E1Event-every(0.2), E2Event-0.5]),
    	repeat, fail.
        e1
        e1
        e2
        e1
        e1
        ^C
        interruption: type a, b, c, e, or h for help : ? e1
        abort
        Aborting execution ...

## See Also

event_create / 3