@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(); }