Passing lambdas to functions in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to pass a lambda that prints "Hello".

Kotlin

fun greet(action: () -> Unit) {
    action()
}

greet([1])

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A-> println("Hello")

Bprintln("Hello")

Cfun() { println("Hello") }

D{ println("Hello") }

Attempts:

3 left

💡 Hint

Common Mistakes

Passing println("Hello") directly without braces.

Using incorrect lambda syntax like '-> println("Hello")'.

The lambda must be passed as a block: { println("Hello") }.

2fill in blank

medium

Complete the code to pass a lambda that returns the sum of two integers.

Kotlin

fun operate(a: Int, b: Int, operation: (Int, Int) -> Int): Int {
    return operation(a, b)
}

val result = operate(3, 4, [1])
println(result)

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A{ x, y -> x + y }

B{ x, y -> x - y }

C{ x, y -> x * y }

D{ x, y -> x / y }

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction, multiplication, or division instead of addition.

Incorrect lambda parameter syntax.

The lambda must add the two parameters: { x, y -> x + y }.

3fill in blank

hard

Fix the error in passing a lambda that prints the given message.

Kotlin

fun printMessage(message: String, action: (String) -> Unit) {
    action(message)
}

printMessage("Hi", [1])

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A{ println(it) }

B{ msg -> println(msg) }

Cprintln

D{ msg -> print(msg) }

Attempts:

3 left

💡 Hint

Common Mistakes

Passing println directly without matching the parameter.

Using { println(it) } without specifying the parameter name.

The lambda must explicitly take a parameter and print it: { msg -> println(msg) }.

4fill in blank

hard

Fill both blanks to create a lambda that filters even numbers and doubles them.

Kotlin

val numbers = listOf(1, 2, 3, 4, 5)
val result = numbers.filter([1]).map([2])
println(result)

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A{ it % 2 == 0 }

B{ it * 2 }

C{ it % 2 != 0 }

D{ it + 2 }

Attempts:

3 left

💡 Hint

Common Mistakes

Filtering odd numbers instead of even.

Adding 2 instead of multiplying by 2 in map.

Filter keeps even numbers: { it % 2 == 0 }. Map doubles them: { it * 2 }.

5fill in blank

hard

Fill all three blanks to create a lambda that sorts strings by length and filters those longer than 3.

Kotlin

val words = listOf("cat", "house", "dog", "elephant")
val filtered = words.sortedBy([1]).filter([2]).map([3])
println(filtered)

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A{ it.length }

B{ it.length > 3 }

C{ it.uppercase() }

D{ it.length < 3 }

Attempts:

3 left

💡 Hint

Common Mistakes

Filtering words shorter than 3 instead of longer.

Not converting words to uppercase in map.

Sort by length: { it.length }. Filter words longer than 3: { it.length > 3 }. Map to uppercase: { it.uppercase() }.