PTOLEMY II - CiteSeerX

Designing Actors
}
}
The prefire() method can also be used to perform an operation that will happen exactly once per
iteration. Consider the prefire method of the Bernoulli actor in figure 5.7:
public boolean prefire() throws IllegalActionException {
if (_random.nextDouble() <
((DoubleToken)(trueProbability.getToken())).doubleValue()) {
_current = true;
} else {
_current = false;
}
return super.prefire();
}
This method selects a new boolean value that will correspond to the token sent during each firing in
that iteration.
5.3.3 Fire
The fire() method is the main point of execution and is generally responsible for reading inputs and
producing outputs. It may also read the current parameter values, and the output may depend on them.
Things to remember when writing fire() methods are:
public class Bernoulli extends RandomSource {
}
public Bernoulli(CompositeEntity container, String name)
throws NameDuplicationException, IllegalActionException {
super(container, name);
}
output.setTypeEquals(BaseType.BOOLEAN);
trueProbability = new Parameter(this, "trueProbability");
trueProbability.setExpression("0.5");
trueProbability.setTypeEquals(BaseType.DOUBLE);
public Parameter trueProbability;
public void fire() {
super.fire();
output.send(0, new BooleanToken(_current));
}
public boolean prefire() throws IllegalActionException {
if (_random.nextDouble() < ((DoubleToken)(trueProbability.getToken())).doubleValue()) {
_current = true;
} else {
_current = false;
}
return super.prefire();
}
private boolean _current;
FIGURE 5.7. Code for the Bernoulli actor, which is not data polymorphic.
164 Ptolemy II