Introduction

Despite the fact that Kotlin is recognized implicitly as an object-oriented language, it is still open to other programming styles and paradigms. Thanks to Kotlin's built-in features, we are able to apply functional programming patterns to our code with ease. Having the possibility to return functions from other functions or to pass a function as a parameter allows us to benefit from a deferred computation. In addition, we are able to return functions, instead of already-computed values, on different layers in the code. This results in the lazy-evaluation feature.

Compared to Scala or other functional programming languages, Kotlin doesn't require us to use dedicated, functional style design patterns. It also lacks some of their out-of-the-box implementations. However, in return, it brings more flexibility to developers as far as software architecture and...