orangy

trait Disposable {
    fun dispose()
}

fun using(value : Disposable, body : ()->Unit) {
    try {
        body()
    } finally {
        value.dispose()
    }

orangy

class Event<T> {
    private val handlers = arrayListOf<(Event<T>.(T) -> Unit)>()
    fun plusAssign(handler: Event<T>.(T) -> Unit) { handlers.add(handler) }
    fun invoke(value: T) { for (handler in handlers) handler(value) }
}
 
val e = Event<String>() // define event
 
fun main(args : Array<String>) {
    e += { println(it) } // subscribe

orangy

data class IBAN(val country: String, val account : String)

// parseIBAN returns nullable IBAN
fun parseIBAN(code : String) : IBAN? {
 ...
}

val iban = parseIBAN(userInput)
when (iban) {
  null -> throw InvalidIBANException()

orangy

when(v) {
  is Vector -> // here v is of type Vector
  is Versor -> // here v is of type Versor
  else -> throw UnsupportedTypeException()
}