An interval is a connected set of values between endpoints. In Kotlin, the `..` operator creates an inclusive range, such as `1..10`, replacing many traditional counter-based `for` loops. section 2.4.2 section 2.6
Iterate through an interval
```kotlin fun main() { for (i in 1..100) { print(fizzBuzz(i)) } } ``` Here, `1..100` supplies each integer from 1 through 100. A progression can change traversal with `downTo` and `step`: `100 downTo 1 step 2` visits descending even numbers.
Use intervals for traversal, membership tests, and comparable values:
- Use `in` and `!in` to test whether a value belongs to an interval, including character checks such as `c in 'a'..'z'`. section 2.4.4
- Create ranges from comparable objects, including dates; `..<` excludes the upper endpoint. section 9.3.3
The `..` operator is shorthand for `rangeTo`. Kotlin’s standard library supports it for comparable elements, while enumerable progressions apply when values can be stepped through, such as numbers and characters. Parenthesize a range before calling a method on it, as in `(0..n).forEach { ... }`. section 9.3.3
