Operators

An operator is a symbol that works on values, such as + or &&.

Arithmetic and assignment

+, -, *, /, %, plus compound assignment and increment:

fun main() {
    var score = 10
    score += 5
    score -= 2
    score *= 2
    score++
    println(score)
}

27

Logical operators

fun main() {
    val age = 20
    val hasTicket = true

    println(age >= 18 && hasTicket)
    println(age < 13 || age > 65)
    println(!hasTicket)
}

true
false
false

• && (and) — true only if both sides are true.
• || (or) — true if either side is true.
• ! (not) — flips true and false.

Kotlin stops as soon as the answer is known: in a && b, if a is false, b is never evaluated.

The in operator

in checks membership — in a range, a collection, or a string:

fun main() {
    val age = 42
    println(age in 18..65)
    println("b" in listOf("a", "b"))
    println(7 !in 1..5)
}

true
true
true

No ternary operator

Kotlin has no condition ? a : b. Because if is an expression, you write if (condition) a else b — covered in the Conditionals lesson.

Practice

A shop gives free delivery if an order is over 50 or the customer is a member. With total = 42 and isMember = true, print whether delivery is free.

fun main() {
    val total = 42
    val isMember = true
    println(total > 50 || isMember)
}

true