Detect two bangs within a given interval

This example demonstrates a way to detect if two events, coming from two different sources, occur within a given interval of time from each other. We use the cpuclock object to detect the time at the moment each event occurs. The output of either cpuclock object in this example will trigger a subtraction calculation between the timings of the most recent event from each source. We calculate the absolute value of the difference between the time of occurrence of those two bang messages to determine the time interval, and then test that value to see if it is less than or equal to 1000 ms. If so, we use the result of that calculation to trigger another event.