Define and call functions

func declares a function. Each ordinary parameter has a name and type. Write the return type after : following the parameter list.

func add(left: int, right: int): int {
    return left + right
}

func main() {
    var result = add(2, 3)
    print(result)
}

add receives two integers and returns their sum. main calls add(2, 3) and prints 5.

Return a result

return expression ends the function and returns a value. Each reachable path in a result-producing function must provide a matching result.

func clamp(value: int): int {
    if value > 10 {
        return 10
    }
    return value
}

func main() {
    print(clamp(15))
}

An omitted return type means void. Use return alone to end a void function early.

Ordinary parameters copy values

func increase(value: int): int {
    value += 1
    return value
}

func main() {
    var count = 2
    var next = increase(count)
    print(count)
    print(next)
}

The output is 2 followed by 3. Pass an address reference to update game data. Use function values and lambdas to pass behavior.

Read-only parameters appear in <...>. Use them for type parameters and compilation settings.