## Calculate a specific number in the fibonacci sequence 
fn fib(n: i32) -> i32 {
    match n {
        0 | 1 => n,
        _ => fib(n - 1) + fib(n - 2),
    }
}

generator fn fib_sequence(range: Range<i32>) -> i32 {
    for n in range {
        yield fib(n);
    }
}

print(fib_sequence(0..20).join(", "))