Run function behavior and use cases in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run the block and return its result.

Kotlin

val result = run [1] {
    5 + 3
}
println(result)

Drag options to blanks, or click blank then click option'

A() -> Int

B{ Int -> Int }

C() -> Unit

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lambda type with parameters instead of none.

Confusing the return type with the lambda parameter type.

The run function takes a lambda with no parameters and returns the lambda's result. The lambda type is () -> Int here.

2fill in blank

medium

Complete the code to run a block on a nullable object safely.

Kotlin

val name: String? = "Kotlin"
val length = name?.run [1] {
    length
} ?: 0
println(length)

Drag options to blanks, or click blank then click option'

A() -> Int

B{ String -> Int }

C() -> String

D{ Int -> Int }

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a parameter to the lambda when using run on an object.

Not handling the nullable case with ?: 0.

The run function called on an object uses the object as this inside the lambda, which takes no parameters. The lambda returns the length of the string.

3fill in blank

hard

Fix the error in the run block to correctly return the last character.

Kotlin

val word = "hello"
val lastChar = run [1] {
    word[word.length]
}
println(lastChar)

Drag options to blanks, or click blank then click option'

A() -> Int

B() -> String

C() -> Char

D() -> Unit

Attempts:

3 left

💡 Hint

Common Mistakes

Using an incorrect lambda type with parameters.

Confusing the return type with the parameter type.

The lambda returns a Char and has no parameters. The index should be word.length - 1 to avoid an error, but the blank is for the lambda type.

4fill in blank

hard

Fill both blanks to create a map of words to their lengths using run.

Kotlin

val words = listOf("apple", "banana", "cherry")
val lengths = words.associateWith [1] {
    it.[2]
}
println(lengths)

Drag options to blanks, or click blank then click option'

Arun

Blength

Ccount

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using count or size instead of length for strings.

Not using run in the first blank.

The associateWith function takes a lambda that returns a value for each element. Using run runs the block on each word, and length gets the word's length.

5fill in blank

hard

Fill all three blanks to filter and map words using run with conditions.

Kotlin

val words = listOf("dog", "cat", "elephant", "fox")
val filtered = words.filter [1] {
    it.length [2] 3
}.map [3] {
    it.uppercase()
}
println(filtered)

Drag options to blanks, or click blank then click option'

Arun

B>

Cfilter

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter or map as the lambda instead of run.

Using the wrong comparison operator.

The filter function takes a lambda to select words longer than 3. Using run runs the lambda on each word. Then map transforms each word to uppercase using run.