val and var

val declares a binding you assign once. After that, the value cannot be reassigned:

val pi = 3.14159
val name = "Ada"
// pi = 3.0   // compile error

Prefer val by default — it makes code easier to follow because the value can't drift.

Implement double(n) so it returns n * 2. Inside the function, declare val factor = 2 and use it.

Starter code

fun double(n: Int): Int {
    val factor = 2
    return n
}

var declares a binding you can reassign as many times as you need:

var count = 0
count = count + 1     // ok
count = count + 1     // ok again
count++               // shorthand for count = count + 1

Compound operators like +=, -=, ++, -- work on var (they all mutate).

Implement stepUp(start) that takes a number, adds 5 to it, then adds 3 more, and returns the result. Do it by reassigning a single var.

Starter code

fun stepUp(start: Int): Int {
    var n = start
    return n
}

They look similar, but they convey very different intent:

val name = "Ada"      // identity — never changes
var score = 0         // counter — designed to change

Rule of thumb: start with val. Switch to var only when you genuinely need to reassign.

Implement bumpFromBase() using both kinds of declaration:

• a val base = 10
• a var n initialised to base
• increment n twice with n++
• return n

Expected: 12.

Starter code

fun bumpFromBase(): Int {
    val base = 10
    var n = base
    return n
}