I’ll agree with that, and I’d add that you need to be sure the index won’t change while you’re not looking so you can know that each position has been visited. Think of a cop checking parking meters, for a relatively low-stakes example. If they get distracted—say, by some irate motorist a few meters away complaining about a ticket from long ago—it would be easy for them to forget if they had processed the closest meter. If they walk/ride toward the motorist to be heard better, they might easily lose their place entirely. In this example, the cop’s physical location acts as an index, which is only good until the cop needs to move in an unexpected way. The distraction can lead to double-touching one or more meters. Worse, the cop might invisibly skip one or more meters unless they are maintaining some more durable kind of history like a checklist or other report.
I’ll agree with that, and I’d add that you need to be sure the index won’t change while you’re not looking so you can know that each position has been visited. Think of a cop checking parking meters, for a relatively low-stakes example. If they get distracted—say, by some irate motorist a few meters away complaining about a ticket from long ago—it would be easy for them to forget if they had processed the closest meter. If they walk/ride toward the motorist to be heard better, they might easily lose their place entirely. In this example, the cop’s physical location acts as an index, which is only good until the cop needs to move in an unexpected way. The distraction can lead to double-touching one or more meters. Worse, the cop might invisibly skip one or more meters unless they are maintaining some more durable kind of history like a checklist or other report.