Kotlin and discriminated unions (sum types)

Question

Does Kotlin have anything like discriminated unions (sum types)? What would be the idiomatic Kotlin translation of this (F#):

type OrderMessage =
    | New of Id         


        

Answer 1

Kotlin's sealed class approach to that problem is extremely similar to the Scala sealed class and sealed trait.

Example (taken from the linked Kotlin article):

sealed class Expr {
    class Const(val number: Double) : Expr()
    class Sum(val e1: Expr, val e2: Expr) : Expr()
    object NotANumber : Expr()
}