Range expressions are formed with ** rangeTo** functions that have the operator form

**..**

which is complemented by **and**

*in***.**

*!in*Range is defined for any comparable type, but for integral primitive types it has an optimized implementation. Here are some examples of using ranges

if ( i in 1 ..Ā 10 ) { // equivalent of 1 <= i && i <= 10 println(i); }

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Integral type ranges ** (IntRange, LongRange, CharRange)** have an extra feature: they can be iterated over. The compiler takes care of converting this analogously to Java’s indexed for-loop, without extra overhead.

for (i in 1..4) print(i) // prints "1234" for (i in 4..1) print(i) // prints nothing

Have you noticed that the second statement prints out nothing. That’s because ** IntRange** is defined by its

*and its*

`minimum start`

*values. In other words, when*

`maximum endInclusive`

*, the range is empty.*

`endInclusive < start`

You can use * downTo()* function which is defined in the standard library to iterate the Range in reverser order.

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Alternatively, you can also use the * progression*. A progression can be any arithmetic sequence, so it can go up or down. Here are two ways to make a decrementing progression:

//Using downTo() function for (i in 4 downTo 1) print(i) // prints "4321" //Using reversed() function (1..3).reversed().forEach(System.out::print)

Can Ranges in Kotlin do the same magic as other language iterator of stepping the numbers more than the default value of 1. Well, the answer is * YES*. Here is the implementation for your quick reference to step the range for the value greater than 1.

for (i in 1..4 step 2) print(i) // prints "13" for (i in 4 downTo 1 step 2) print(i) // prints "42"

Another great point in Ranges is not to include the last element in the Range.

for (i in 1 until 10) { // i in [1, 10), 10 is excluded println(i) }

Well this is just the glimpse of the Ranges in Kotlin, in the next journal entry we will try to explore how internally this works.

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