In most functional programming languages, there is a type called Either (or a synonym). The
Either type is used to represent a value that can have two possible types. It is common to see
Either used to represent a success value or a failure value, although that doesn't have to be the case.
Although Kotlin doesn't come with an
Either as part of the standard library, it's very easy to add one.
Let's start by defining a sealed abstract class with two implementations for each of the two possible types that
Either will represent:
sealed class Either<out L, out R> class Left<out L>(value: L) : Either<L, Nothing>() class Right<out R>(value: R) : Either<Nothing, R>()
It is usual to call the two implementations
Right. By convention, when ...