Kotlin range is defined by its two endpoint values which are both included in the range. Kotlin ranges are created with rangeTo() function, or simply using downTo or (. .) operators. The main operation on ranges is contains, which is usually used in the form of in and !in operators.
Example
1..10// Range of integers starting from 1 to 10
a..z // Range of characters starting from a to z
A..Z // Range of capital characters starting from A to ZBoth the ends of the range are always included in the range which means that the 1..4 expression corresponds to the values 1,2,3 and 4.
Creating Ranges using rangeTo()
To create a Kotlin range we call rangeTo() function on the range start value and provide the end value as an argument.
Example
funmain(args: Array<String>){for( num in1.rangeTo(4)){println(num)}}When you run the above Kotlin program, it will generate the following output:
1
2
3
4
Creating Ranges using .. Operator
The rangeTo() is often called in its operator form ... So the above code can be re-written using .. operator as follows:
Example
funmain(args: Array<String>){for( num in1..4){println(num)}}When you run the above Kotlin program, it will generate the following output:
1
2
3
4
Creating Ranges using downTo() Operator
If we want to define a backward range we can use the downTo operator:
Example
funmain(args: Array<String>){for( num in4 downTo 1){println(num)}}When you run the above Kotlin program, it will generate the following output:
4
3
2
1
Kotlin step() Function
We can use step() function to define the distance between the values of the range. Let’s have a look at the following example:
Example
funmain(args: Array<String>){for( num in1..10 step 2){println(num)}}When you run the above Kotlin program, it will generate the following output:
1
3
5
7
9
Kotlin range of Characters
Ranges can be created for characters like we have created them for integer values.
Example
funmain(args: Array<String>){for( ch in'a'..'d'){println(ch)}}When you run the above Kotlin program, it will generate the following output:
a
b
c
d
Kotlin reversed() Function
The function reversed() can be used to reverse the values of a range.
Example
funmain(args: Array<String>){for( num in(1..5).reversed()){println(num)}}When you run the above Kotlin program, it will generate the following output:
5
4
3
2
1
Kotlin until() Function
The function until() can be used to create a range but it will skip the last element given.
Example
funmain(args: Array<String>){for( num in1 until 5){println(num)}}When you run the above Kotlin program, it will generate the following output:
1
2
3
4
The last, first, step Elements
We can use first, last and step properties of a range to find the first, the last value or the step of a range.
Example
funmain(args: Array<String>){println((5..10).first)println((5..10 step 2).step)println((5..10).reversed().last)}When you run the above Kotlin program, it will generate the following output:
5
2
5
Filtering Ranges
The filter() function will return a list of elements matching a given predicate:
Example
funmain(args: Array<String>){val a =1..10val f = a.filter{ T -> T %2==0}println(f)}When you run the above Kotlin program, it will generate the following output:
[2, 4, 6, 8, 10]
Distinct Values in a Range
The distinct() function will return a list of distinct values from a range having repeated values:
Example
funmain(args: Array<String>){val a =listOf(1,1,2,4,4,6,10)println(a.distinct())}When you run the above Kotlin program, it will generate the following output:
[1, 2, 4, 6, 10]
Range Utility Functions
There are many other useful functions we can apply to our range, like min, max, sum, average, count:
Example
funmain(args: Array<String>){val a =1..10println(a.min())println(a.max())println(a.sum())println(a.average())println(a.count())}When you run the above Kotlin program, it will generate the following output:
1
10
55
5.5
10
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