Level 5. Variables: Labelled Boxes

Imagine you have a box and you stick a label on it. That’s what let does — it creates a named box and puts a value inside.

fun main() {
  let snack = "Apple"
  let count = 5
  println(count)
}

Labelling the box (optional)

You can tell the computer what type of value the box should hold:

let age: int = 11
let name: string = "Alicia"

This is called a type annotation. It’s optional: the compiler is smart enough to figure it out. But sometimes it helps to be explicit.

Rules for variable names

• Must start with a letter or underscore (_).
• Can contain letters, numbers, and underscores.
• Are case-sensitive — score and Score are different boxes.
• Use underscores for multi-word names: high_score, not high-score.

The Last Line Rule

In Hica, you don’t need to say “return.” The computer just looks at the very last line of a block { } and says, “That’s the answer!”

fun main() {
  let a = 10
  let b = 20
  println(b)            // The computer prints 20!
}

🎯 Try it: What happens if you put a on the last line instead of b?

Changeable boxes with var

Sometimes you need a box whose contents can change, like a scoreboard during a game. Use var instead of let:

fun main() {
  var score = 0
  score = score + 10
  score = score + 5
  println(score)          // 15
}

With let, the box is sealed. You can never change what’s inside. With var, the box has a lid. You can open it and swap the contents.

Most of the time, let is all you need. Use var when you really need to update a value, like counting things in a loop (you’ll see this later!).