@Override
public final void compute() {
if (input[0].isDefined() && input[1].isDefined()) {
double param = a.getDouble();
double val = b.getDouble();
try {
PoissonDistribution dist = getPoissonDistribution(param);
double result = dist.inverseCumulativeProbability(val);
// eg InversePascal[1,1,1] returns 2147483647
if (result >= Integer.MAX_VALUE) num.setUndefined();
else num.setValue(result + 1);
} catch (Exception e) {
num.setUndefined();
}
} else num.setUndefined();
}
