I’m not a regular StackOverflow user, neither as a contributor, nor to ask questions. However, I recently stumbled upon a question, tried to help…​ and failed. I was pointed out my answer was wrong - thanks for everyone who did. I think failures are great occasions to learn something new! In this post, I’d like to detail what I learned after digging further: there are several ways to combine elements from an existing collection in Kotlin stdlib.

IMHO, Kotlin is not about big killer features - although extension methods and properties could certainly be categorized as such, but about a bunch of small improvements that have deep impact. Most of them are not built-in into the language, but are functions offered as part of the Kotlin standard library. In this post, I’d like to go through a limited set of them, and describe how they can be used to improve the code.