Kotlin equivalent of some F# code matching on union type

Question

I'm learning Kotlin and am wondering if anyone out there could advise on what the following snippet of F# might look like in idiomatic Kotlin.

// a function that has an Option<int> as input
let printOption x = match x with
| Some i -> printfn "The int is %i" i
| None -> printfn "No value"

Thanks a million. (btw, the snippet is from Scott Wlaschin's wonderful Domain Modeling Made Functional)

Answer 1

// as a function
fun printOption(x: Int?) {
  when(x) {
    null -> print("No Value")
    42 -> print("Value is 42")
    else -> print("Value is $x")
  } 
}

// as a functional type stored in printOption
val printOption: (Int?) -> Unit = { x ->
  when(x) {
    null -> print("No Value")
    42 -> print("Value is 42")
    else -> print("Value is $x")
  } 
}

You can pass this function type like any other variable and call it like:

printOption(42)
// or
printOption.invoke(42)

Documentation

• Higher-Order Functions and Lambdas
• Kotlin | Function Type, Lambda and Higher-Order Functions