Generic function declaration in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic function that returns the input value.

Kotlin

fun <T> identity(value: [1]): T {
    return value
}

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

AT

BAny

CInt

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using a concrete type like Int or String instead of the generic type T.

Using Any instead of the generic type T.

The generic type T is used as the parameter type to make the function generic.

2fill in blank

medium

Complete the code to declare a generic function that swaps two values in a Pair.

Kotlin

fun <T> swap(pair: Pair<T, T>): Pair<T, T> {
    return Pair(pair.second, [1])
}

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Apair

Bpair.first

Cpair.second

Dpair.swap

Attempts:

3 left

💡 Hint

Common Mistakes

Using pair.second twice instead of pair.first for the second element.

Trying to call a non-existent swap method on pair.

The function returns a new Pair with the first and second values swapped. So the second value is paired with the original first value.

3fill in blank

hard

Fix the error in the generic function declaration that returns the first element of a list.

Kotlin

fun <T> firstElement(list: List<[1]>): T? {
    return list.firstOrNull()
}

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AAny

BList

CT

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a concrete type like Int instead of the generic type T.

Using List without a type parameter.

The generic type parameter T must be used inside the List type to match the function's return type.

4fill in blank

hard

Fill both blanks to declare a generic function that returns the size of a collection.

Kotlin

fun <[1]> collectionSize(collection: Collection<[2]>): Int {
    return collection.size
}

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AT

BInt

DE

Attempts:

3 left

💡 Hint

Common Mistakes

Using different generic type names in declaration and parameter.

Using a concrete type like Int instead of a generic type.

The generic type parameter is declared as T and used as the element type of the collection.

5fill in blank

hard

Fill all three blanks to declare a generic function that returns a map from keys to values filtered by a predicate.

Kotlin

fun <[1], [2]> filterMap(
    map: Map<[1], [2]>,
    predicate: ([3], [2]) -> Boolean
): Map<[1], [2]> {
    return map.filter { (key, value) -> predicate(key, value) }
}

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

AK

BV

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of generic types.

Using inconsistent generic type names.

The generic types are declared as K and V for key and value respectively. They are used consistently in the Map and predicate types.