Functions

Functions use fun. Each parameter has a type, and the return type follows the parameter list:

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

add(2, 3)        // 5

Functions can be called from anywhere main can reach them. They're typed end-to-end — the compiler will yell if you pass a String where it expects an Int.

Write the entire function from scratch this time — no starter scaffold. Declare add so it takes two Int parameters and returns their sum.

Reminder of the shape from the previous step:

fun NAME(p1: TYPE, p2: TYPE): RETURN_TYPE {
    return ...
}

Starter code

// Declare your add function below.
// It should take two Int parameters and return their sum.

Parameters can have defaults — callers can omit them:

fun greet(name: String, excited: Boolean = false): String =
    if (excited) "Hi, $name!" else "Hi, $name."

greet("Ada")              // "Hi, Ada."
greet("Bob", true)        // "Hi, Bob!"

You can also pass arguments by name — much clearer at the call site:

greet(name = "Eve", excited = true)     // "Hi, Eve!"

Named arguments are great when a function takes booleans or several similar parameters.

Two things to do this time:

1. Give the excited parameter a default value of false (so callers can omit it). The harness calls greet("Ada") with no second argument — without a default, that won't even compile.
2. Implement the body:
   • excited = true → "Hello, NAME!"
   • excited = false (the default) → "Hello, NAME."

Reminder of the syntax:

fun foo(x: Int, flag: Boolean = false): String { ... }

Starter code

// Add a default value of `false` to `excited` so callers can call greet("Ada"),
// then fill in the body.
fun greet(name: String, excited: Boolean): String {
    return ""
}

When the body is a single expression, you can drop the braces and the return keyword. The function uses = instead:

fun double(x: Int): Int = x * 2
fun isOdd(n: Int) = n % 2 != 0       // return type inferred

This is idiomatic for short helpers, especially predicates and small calculations.

Convert isEven to single-expression form returning n % 2 == 0. Replace the function body entirely with = n % 2 == 0.

Starter code

fun isEven(n: Int): Boolean = false