length := fn(ptr: ^u8): int {
    len := 0;
    loop if *ptr == 0 break else {
		len += 1;
        ptr += 1;
	}
    return len;
}

display_int := fn(num: int): ^u8 {
    p := page;
    i := 0;
    if num == 0 {
        set(p, 48);
        return p;
    }
    loop {
        if num == 0 break;
        set(p + i, num % 10 + 48);
        num /= 10;
        i += 1;
    }
    reverse(p);
    //null terminate
    set(p + i, 0);
    return p;
}

reverse := fn(s: ^u8): void {
    //reverse a string, don't remove digits
    len := 0;
    loop {
        if *(s + len) == 0 break;
        len += 1;
    }
    i := 0;
    j := len - 1;
    loop {
        if i >= j break;
        temp := *(s + i);
        *(s + i) = *(s + j);
        *(s + j) = temp;
        i += 1;
        j -= 1;
    }
    return;
}

set := fn(change: ^int, new: int): void {
    *(change) = new;
    return;
}