Local functions (nested functions) in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested local function call

What is the output of this Kotlin code with a local function inside another function?

Kotlin

fun outer() {
    fun inner() {
        println("Hello from inner")
    }
    inner()
    println("Hello from outer")
}

fun main() {
    outer()
}

A Hello from inner

B

Hello from outer
Hello from inner

C Compilation error: inner function cannot be called

D

Hello from inner
Hello from outer

💡 Hint

Remember that local functions can be called inside their enclosing function.

The local function 'inner' is called first, printing its message, then the outer function prints its message.

❓ Predict Output

intermediate

Value returned by nested local function

What value does the function 'outer' return when called?

Kotlin

fun outer(): Int {
    fun inner(x: Int): Int {
        return x * 2
    }
    return inner(5) + 3
}

fun main() {
    println(outer())
}

A 13

B 10

C 8

D Compilation error: cannot return from local function

💡 Hint

Calculate inner(5) first, then add 3.

inner(5) returns 10, adding 3 gives 13.

🔧 Debug

advanced

Identify the error in nested function usage

What error does this Kotlin code produce?

Kotlin

fun outer() {
    inner()
    fun inner() {
        println("Inside inner")
    }
}

fun main() {
    outer()
}

A Compilation error: local function cannot be declared after usage

B Unresolved reference: inner

C Runtime exception: inner function not found

D No error, prints "Inside inner"

💡 Hint

Check the order of function declaration and usage.

The local function 'inner' is called before it is declared, causing an unresolved reference error.

❓ Predict Output

advanced

Effect of local function modifying outer variable

What is the output of this Kotlin code?

Kotlin

fun outer() {
    var count = 0
    fun increment() {
        count += 1
    }
    increment()
    increment()
    println(count)
}

fun main() {
    outer()
}

A 2

B 0

C 1

D Compilation error: cannot modify outer variable

💡 Hint

Local functions can access and modify variables from the outer function.

The local function increments 'count' twice, so the final value is 2.

🧠 Conceptual

expert

Scope and visibility of local functions

Which statement about local functions in Kotlin is TRUE?

A Local functions can be declared at the top level outside any function.

B Local functions can be accessed from any other function in the same file.

C Local functions can be called only inside the function where they are declared.

D Local functions can be called before their declaration anywhere in the program.

💡 Hint

Think about the visibility and scope rules of local functions.

Local functions are only visible and callable inside the function where they are declared.