Returning Function from Function in Kotlin

Introduction

Returning Function from Function is a fundamental concept every Kotlin developer should understand. Higher-order functions accept or return other functions, enabling reusable patterns like map, filter, and custom control abstractions.

A function can return another function as its result. In this tutorial you will learn the syntax, walk through a complete example program, study the sample output, and review best practices so you can apply the concept confidently in your own projects.

Definition

• A function can return another function as its result.
• Returned function can capture values from outer scope.
• Useful for configurable behavior.

Syntax

fun multiplier(factor: Int): (Int) -> Int

Returning Function from Function in Kotlin Example Program in Kotlin

fun multiplier(factor: Int): (Int) -> Int {
    return { value -> value * factor }
}

fun main(args: Array<String>) {
    val triple = multiplier(3)
    println(triple(4))
}

Sample Output

12

When to use

Use higher-order functions to extract repeated control-flow patterns into reusable abstractions.

How it works

1. The program starts with a main function — the entry point that runs when you execute the file.

2. val triple = multiplier(3) assigns or updates a value used later in the program.

3. The println(triple(4)) statement writes a line to the console — this produces part of the sample output below.

4. A function can return another function as its result.

5. Run the program in IntelliJ IDEA, Android Studio, or with the Kotlin command-line compiler (kotlinc / kotlin). Compare your console output with the sample output shown below.

Best Practices

• Understand the core idea: a function can return another function as its result.
• Prefer readable names and small functions so examples map directly to real projects.
• Run and modify the example — change values and observe how the output changes.

Common Mistakes

• Skipping the example and only reading the definition — hands-on practice cements the concept.
• Copying syntax without understanding nullable vs non-nullable types or scope rules.
• Ignoring compiler warnings that often point to safer alternatives.

Key Points

• A function can return another function as its result.
• Returned function can capture values from outer scope.
• Useful for configurable behavior.
• Test the example locally and verify the output matches the sample.
• Experiment by changing input values to see how behaviour changes.

Notes

• Semicolons at the end of statements are optional in Kotlin.