Functional Kotlin

Option

The Option<T> datatype is the representation of a presence or absence of a value T. In Arrow, Option<T> is a sealed class with two sub-types, Some<T>, a data class that represents the presence of value T and None, and an object that represents the absence of value. Defined as a sealed class, Option<T> can't have any other sub-types; therefore the compiler can check clauses exhaustively, if both cases, Some<T> and None are covered.

I know (or I pretend to know) what you're thinking at this very moment—why do I need Option<T> to represent the presence or absence of T, if in Kotlin we already have T for presence and T? for absence?

And you are right. But Option provides a lot more value than nullable types, let's jump directly to an example: ...