In Kotlin, you can use ranges and step values in for loops to iterate over a sequence of numbers or characters. Here’s a detailed guide:

1. Ranges in Kotlin

A range is defined using the .. operator. For example:

for (i in 1..5) {
    println(i)
}

• Output: 1 2 3 4 5
• The loop iterates from 1 to 5 (both inclusive).

2. Stepping Through a Range

To define the step value, you can use the step function. For instance:

for (i in 1..10 step 2) {
    println(i)
}

• Output: 1 3 5 7 9
• The loop starts from 1 and increments by 2 on each iteration.

3. Descending Ranges

If you want to iterate in reverse order, use the downTo function:

for (i in 10 downTo 1) {
    println(i)
}

• Output: 10 9 8 7 6 5 4 3 2 1

You can combine downTo with step:

for (i in 10 downTo 1 step 2) {
    println(i)
}

• Output: 10 8 6 4 2

4. Iterating Over Characters

Kotlin ranges also work with characters:

for (ch in 'a'..'e') {
    println(ch)
}

• Output: a b c d e

You can also provide a step value:

for (ch in 'a'..'z' step 3) {
    println(ch)
}

• Output: a d g j m p s v y

5. Using until

The until function creates a range that excludes the upper boundary:

for (i in 1 until 5) {
    println(i)
}

• Output: 1 2 3 4
• The loop stops before reaching 5.

Summary of Functions and Keywords

1. ..: Creates a range that includes the start and end values.
2. downTo: Creates a descending range.
3. step: Sets the step value for the range.
4. until: Excludes the upper boundary of the range.

These features make Kotlin’s for loops flexible and expressive.