Your First Program

Create a file called hello.rk:

func main() {
    println("Hello, Rask!")
}

Run it:

rask run hello.rk

Output:

Hello, Rask!

What’s Happening?

• func main() is the program entry point
• println() is a builtin for printing with newline

Variables

Let’s try variables:

func main() {
    let name = "Rask"
    mut year = 2026
    year += 1
    println(format("Hello from {} in {}!", name, year))
}

• let binds a name once: no reassignment, and no mutating the value either (you can still move it — handing ownership away isn’t mutation)
• mut is what you reach for when the value needs to change — reassignment or a mutating method like v.push(x)
• Types are inferred, but you can write them explicitly: let year: i64 = 2026

const exists too, but it’s only for module-level constants — not for locals inside a function.

Functions

func greet(name: string) {
    println(format("Hello, {}!", name))
}

func main() {
    greet("World")
}

Functions that return values need explicit return:

func add(a: i32, b: i32) -> i32 {
    return a + b
}

func main() {
    let result = add(2, 3)
    println(format("2 + 3 = {}", result))
}

Next: Explore the Guide

Next: Passing Values, on what happens to a value when you hand it to a function.