divide & modulo strings

string divide(string a, string b)
{
    string xtimes = "0";
    while(compare(a, ">=", b))
    {
        a = subtracting(a, b);
        xtimes = adding(xtimes, "1");
    }
    return xtimes;
}

string modulo(string a, string b)
{
    while(compare(a, ">=", b))
        a = subtracting(a, b);
    return a;
}