Q. Is it better to use postfix or prefix?
A. This depends on the needs of your calculations. There is no performance gain using one or the other; it purely depends on how you need to use them. For instance, ++a and a++ both increment a, but the former increments before returning its value, and the latter returns its value and then increments. Be careful of this distinction in your code.
Q. Why are there two range operators? Wouldn’t it be simpler to just use one?
A. Having two range operators allows you to express intent a lot more clearly in code. In the case of a zero-based list, you may have 10 items but the last item’s index is 9, so a half-closed range operator (0..<count, for instance) would be a better fit. If you know you have a finite number of times something should loop, a closed-range operator (1...10, for instance) clearly indicates a range of 1 to 10.
Q. What is a practical example of using remainder?
A. Imagine an app that shows a progress bar when loading. In this case, the progress is only checked occasionally (every nth time) throughout the loading loop, or when the count of the loop % n is equal to 0. This becomes clearer in later hours when we cover conditionals and control flow in Hour 5 and loops in Hour 7.