TimeString timestr;

// trying to get one of these to work
bool check = timestr("the_string").is_valid
bool check = timestr("the_string")->is_valid
bool check = timestr("the_string")

// here is the class
class TimeString {
private:
    vector<string> str_vec;
    int h, m;
    double s, total_sec;
    string timestr;

    void to_timestr(const string& str) {
        if (timestr == str) return;
        is_valid = true;
        str_vec = split(str, ':', 3, "0");
        if (is_number(str_vec[2])) {
            h = ToI(str_vec[2]);
            total_sec += h * 3600;
        }
        else is_valid = false; return;

        if (is_number(str_vec[1])) {
            m = ToI(str_vec[1]);
            total_sec += m * 60;
        }
        else is_valid = false; return;

        if (is_number(str_vec[2])) {
            s = ToI(str_vec[2]);
            total_sec += s;
        }
        else is_valid = false; return;
        timestr.clear();

        return;
    }

    void to_timestr(double sec) {
        is_valid = true;
        str_vec.resize(3, "0");
        total_sec = sec;

        h = sec / 3600;
        s = sec - h * 3600;
        m = s / 60;
        s = sec - m * 60;
        timestr.pop_back();
    }

public:
    TimeString() {};

    bool is_valid = false;

    TimeString(const string& str) { to_timestr(str); }

    TimeString operator=(const char* str) {
        to_timestr(str);
        return *this;
    }

    //TimeString operator=(double sec) {
    //  to_timestr(sec);
    //  return *this;
    //}

    //operator const string() {
    //  if (!is_valid) return "";
    //  if (timestr.size()) return timestr;
    //  if (h) timestr += ToS(h) + ":";
    //  if (m) timestr += ToS(m) + ":";
    //  if (s) timestr += ToS(s) + ":";
    //  return *this;
    //}

    //operator const double() { return total_sec; }

    //operator const bool() { return is_valid; }
};