Ranges

Before you dive into the for loop statement, you need to know about the Range data type, which lets you represent a sequence of numbers. Let’s look at two types of Range.

First, there’s closed range, which you represent like so:

let closedRange = 0...5

The three dots (...) indicate that this range is closed, which means the range goes from 0 to 5 inclusive. That’s the numbers (0, 1, 2, 3, 4, 5).

Second, there’s half-open range, which you represent like so:

let halfOpenRange = 0..<5

Here, you replace the three dots with two dots and a less-than sign (..<). Half-open means the range goes from 0 to 5, inclusive of 0 but not of 5. That’s the numbers (0, 1, 2, 3, 4).

Both open and half-open ranges must always be increasing. In other words, the second number must always be greater than or equal to the first.

Ranges are commonly used in both for loops and switch statements, which means that throughout the rest of the chapter, you’ll use ranges as well!