Kotlin operators

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Goal

Read and write Kotlin arithmetic, comparison, and logical expressions. After this page you will recognise every operator that appears in this tier's code samples.

Prerequisites

• Variables and types

Arithmetic

The five arithmetic operators behave the same as in most languages:

Operator	Meaning
+	add
-	subtract
*	multiply
/	divide
%	remainder

fun main() {
    val a = 100
    val b = 6
    println(a + b) // 106
    println(a / b) // 16  — Int / Int truncates
    println(a % b) // 4
}

Integer division truncates. If you want a decimal result, convert at least one side:

fun main() {
    val a = 100
    val b = 6
    println(a.toDouble() / b) // 16.666666666666668
}

Assignment

= assigns. The compound forms (+=, -=, *=, /=, %=) require a var:

fun main() {
    var total = 10
    total += 5
    total *= 2
    println(total) // 30
}

Comparison

Comparisons return Boolean:

Operator	Meaning
==	equal
!=	not equal
>	greater than
<	less than
>=	greater or equal
<=	less or equal

Kotlin's == is structural equality (same value). Reference equality uses === and you almost never need it at this tier.

fun main() {
    val price = 25
    println(price == 25) // true
    println(price >= 30) // false
}

Logical

Three logical operators combine Boolean values:

Operator	Meaning
&&	both true
||	either true
!	invert

fun main() {
    val age = 28
    val isMonday = true
    val getsDiscount = age in 13..60 && isMonday
    println(getsDiscount) // true
}

age in 13..60 is the range check — handy for the lookups you'll see in the next page's lambda example.

Next → Functions and lambdas