Summary - Functions

Combine expression body, default and named arguments to write a math helper.

Summary: expression body, default and named together

In this summary you will combine the expression body (=), a default parameter and named arguments. The one-line fun greet(name: String, msg: String = "Hello") = println("$msg $name") is both short and flexible.

fun greet(name: String, msg: String = "Hello") =
    println("$msg $name")
greet("Ava")                 // Hello Ava
greet(name = "Ava", msg = "Hi")  // Hi Ava

These three features together provide both short writing and flexibility on the caller side; the usage forms of the function fold into one definition.

Exercise Expression body + default + named call

Define fun greet(name: String, msg: String = "Hello") = println("$msg $name") (expression body). From main call it with a named argument: greet(name = "Ava").

Show example solution

fun main() {
    greet(name = "Ava")
}

fun greet(name: String, msg: String = "Hello") = println("$msg $name")

Exercise Expression body + default for add

Define fun add(a: Int, b: Int = 0): Int = a + b (expression body). From main print the result with println(add(5)).

Show example solution

fun main() {
    println(add(5))
}

fun add(a: Int, b: Int = 0): Int = a + b

Test yourself

Which definition combines all three features?
- fun greet(name, msg) { println("$msg $name") }; greet("Ava")
- fun greet(name: String = "Ava"): String = "Hi"
- fun greet(name: String) = println(name); greet(name = "Ava")
- fun greet(name: String, msg: String = "Hi") = println("$msg $name"); greet(name = "Ava")
Show answer

fun greet(name: String, msg: String = "Hi") = println("$msg $name"); greet(name = "Ava") — Expression body (=), default msg and named call are all present.

Fill in the blank: named argument

greet(name ____ "Ava", msg = "Hi")

Show answer

greet(name = "Ava", msg = "Hi")

Next lesson: Nullable types

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