fn checksum(bytes: Span<u8>) -> u32 {
    var sum: u32 = 0
    var i: usize = 0
    while i < std.mem.len(bytes) {
        sum = (sum + bytes[i] as u32) % 256
        i = i + 1
    }
    return sum
}

pub fn main(world: World) -> Void raises {
    if checksum(std.mem.span("abc")) == 38 {
        check world.out.write("crc ok\n")
    }
}