Hi Barry, the output for that case is a boolean value, not a number value. But if you want a number to be output instead, try switching the output type to:

this.addOutput("Out","number");

Then in onExecute, try this:

this.setOutputData(0, output.length == 0 ? 0 : 1);

The "output.length == 0 ? 0 : 1" part is a compact way of saying: "if output length is 0 output 0 else output 1".

- Michael