Collection Operations: Transformations

An introduction to the most important collection transformations — map, flatMap, flatten, intersection, union, subtract, sorted, reverse, associate, zip, unzip, and their variants.

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THE CURRENT VERSION OF THIS ARTICLE IS PUBLISHED HERE.

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Tags: #FYI++

This article is part of the Kotlin Primer, an opinionated guide to the Kotlin language, which is indented to help facilitate Kotlin adoption inside Java-centric organizations. It was originally written as an organizational learning resource for Etnetera a.s. and I would like to express my sincere gratitude for their support.

It is recommended to read the Introduction before moving on. Check out the Table of Contents for all articles.

Element-wise Transformations

map

inline fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R>

The most fundamental collection transformation, and the most often used, is map, which accepts a lambda and…