Functions

A function is a reusable block of code that performs a specific task

You can pass data, known as parameters, into a function

Functions help you organize and reuse code by defining logic once and calling it multiple times

Use the func keyword to declare a function

Create a function

func functionName() {
  // code to be executed
}

Example

func greet() {
  println("Hello world")
}

greet()

Parameters

You can pass parameters into a function

func functionName(parameter1: type, parameter2: type, ...) {
  // code to be executed
}

Function parameters are immutable by default

Example

func greet(name: String) {
  println("Hello " + name)
  //name = "hi" wrong because parameters are immutable
}

greet("John")

Return value

If a function returns a value, you must declare its return type

func functionName(parameter1: type, parameter2: type, ...): type {
  // code to be executed
}

Use the return keyword to return a value

func add(a: Int, b: Int): Int {
  return a + b
}

val result = add(3, 5)
println(result)
//>> 8

Single-expression function

If a function contains only a single expression, you can use the shorthand syntax.

The expression result will be returned automatically.

func functionName(parameter1: type, parameter2: type, ...) = expression
func functionName(parameter1: type, parameter2: type, ...): type = expression

Example

func plus(a: Int, b: Int): Int = a + b

println(plus(2, 3))
//>> 5