fn fib(n: u32) -> u32 {
    var index: u32 = 0
    var a: u32 = 0
    var b: u32 = 1
    while index < n {
        let next: u32 = a + b
        a = b
        b = next
        index = index + 1
    }
    return a
}

fn fibSum(max: u32) -> u32 {
    var index: u32 = 0
    var sum: u32 = 0
    while index <= max {
        sum = sum + fib(index)
        index = index + 1
    }
    return sum
}

pub fn main(world: World) -> Void raises {
    if fib(0) == 0 && fib(1) == 1 && (fib(2) == 1 && fib(10) == 55) && fibSum(10) == 143 {
        check world.out.write("fibonacci ok\n")
    }
}