Kotlin supports the concept of ranges, which represent sequences of comparable types. To create a range, we can use the rangeTo methods that are implemented in classes, such as Int, in the following way:

public operator fun rangeTo(other: Byte): LongRange = LongRange(this, other)

public operator fun rangeTo(other: Short): LongRange = LongRange(this, other)

public operator fun rangeTo(other: Int): LongRange = LongRange(this, other)

public operator fun rangeTo(other: Long): LongRange = LongRange(this, other)

So, we have two options for creating a range, as follows:

• Using the rangeTo method. This may look as follows—1.rangeTo(100).
• Using the .. operator. This may look as follows—1..100.

Ranges are extremely useful when we work with loops:

for (i in 0..100) {
    // .....
}

The 0..100 range is equal to the  1 <= i && i <= 100 statement.

If you want to exclude the last value, you can use the until function, in the following way:

0 until 100

We can also use the step function, as follows:

1..100 step 2

The preceding snippet represents a range like the following:

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, ... 99]

It's worth mentioning that ranges support a lot of until functions, such as filter or map:

(0..100)
        .filter { it > 50 }
        .map { it * 2 }