2 years ago

Intervals or ranges pop-up everywhere in the programming world. The classic example is picking a start and end date, like you would when booking an AirBnB or a flight. But that's just one example: from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice, to Java's https://docs.oracle.com/javase/8/docs/api/java/util/List.html and even SQL's LIMIT operator, ranges are everywhere. Have you ever wondered why they are always implemented as [closed, open) as opposed to [closed, closed]?

A closed-open interval, usually denoted as [a, b) is just a short form for expressing a