Kotlin List zip()
Syntax & Examples

Syntax of List.zip()

There are 4 variations for the syntax of List.zip() extension function. They are:

infix fun <T, R> Iterable<T>.zip( other: Array<out R> ): List<Pair<T, R>>

This extension function returns a list of pairs built from the elements of this collection and the other array with the same index. The returned list has length of the shortest collection.

fun <T, R, V> Iterable<T>.zip( other: Array<out R>, transform: (a: T, b: R) -> V ): List<V>

This extension function returns a list of values built from the elements of this collection and the other array with the same index using the provided transform function applied to each pair of elements. The returned list has length of the shortest collection.

infix fun <T, R> Iterable<T>.zip( other: Iterable<R> ): List<Pair<T, R>>

This extension function returns a list of pairs built from the elements of this collection and other collection with the same index. The returned list has length of the shortest collection.

fun <T, R, V> Iterable<T>.zip( other: Iterable<R>, transform: (a: T, b: R) -> V ): List<V>

This extension function returns a list of values built from the elements of this collection and the other collection with the same index using the provided transform function applied to each pair of elements. The returned list has length of the shortest collection.

✐ Examples

1 Example

In this example,

We create a list named list1 containing integers 1, 2, and 3.
We create an array named array2 containing integers 4, 5, and 6.
We use the zip function to combine elements of list1 and array2 into pairs.
Since both collections have the same length, the resulting list contains pairs of corresponding elements.
Finally, we print the zipped list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf(1, 2, 3);
    val array2 = arrayOf(4, 5, 6);
    val zipped = list1.zip(array2);
    println(zipped);
}

Output

[(1, 4), (2, 5), (3, 6)]

2 Example

In this example,

We create a list named list1 containing characters 'a', 'b', and 'c'.
We create an array named array2 containing characters 'x', 'y', and 'z'.
We use the zip function to combine elements of list1 and array2 into strings by concatenating corresponding elements.
Finally, we print the zipped list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf('a', 'b', 'c');
    val array2 = arrayOf('x', 'y', 'z');
    val zipped = list1.zip(array2) { a, b -> "$a$b" };
    println(zipped);
}

Output

[ax, by, cz]

3 Example

In this example,

We create a list named list1 containing strings "apple", "banana", and "cherry".
We create another list named list2 containing integers 1 and 2.
We use the zip function to combine elements of list1 and list2 into pairs.
Since list2 is shorter than list1, only the first two elements of list1 are paired with the corresponding elements of list2.
Finally, we print the zipped list to standard output.

Kotlin Program

fun main(args: Array<String>) {
    val list1 = listOf("apple", "banana", "cherry");
    val list2 = listOf(1, 2);
    val zipped = list1.zip(list2);
    println(zipped);
}

Output

[(apple, 1), (banana, 2)]

Summary

In this Kotlin tutorial, we learned about zip() extension function of List: the syntax and few working examples with output and detailed explanation for each example.