Hands-On Object-Oriented Programming with Kotlin

Functions with default arguments

Kotlin makes it possible to assign a value to a parameter in the function declaration. If the function is invoked without passing a value, then the compiler automatically assigns a default value to it. The hello function prints Hello Kotlin if no value is passed to the function:

fun hello(message : String = "Kotlin") : Unit{     println("Hello $message")} fun main (args: Array<String>) {    hello()     hello("World")}

The default argument is a very helpful feature in many situations. For example, consider a situation in which we are writing a currency exchange function that converts dollars into another currency and applies service charges on the conversion:

fun currencyExchange(dollar: Double, currencyRate: Double, ...