Kotlin·Kotlin from syntax to a coroutine app

Functions and lambdas

Use default arguments, named arguments and higher-order functions.

Beginner 12 min read Lesson 3 of 300 Challenge included

What you will be able to do

Use default arguments instead of overloads.
Use named arguments for clarity.
Pass lambdas as the last parameter.
Use function references with ::.

In plain English

Functions are values. Lambdas and function references let you pass behaviour. Default and named arguments remove overload boilerplate and make call sites readable.

Functions.ktKotlin

fun format(minutes: Int, suffix: String = "min") = "$minutes $suffix"

fun applyTwice(value: Int, transform: (Int) -> Int): Int = transform(transform(value))

fun main() {
    println(format(12))
    println(applyTwice(3) { it * 2 })
}

Your turn

Write a trailing lambda

Easy

Call applyTwice(2) with a lambda that adds one.

KOTLIN · starter

applyTwice(2)

Check your understanding before moving on.

Knowledge checkQuestion 1

What does a higher-order function accept?

Select an answer to continue

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