C++实现Date日期类

定义一个Date类，包含三个属性年、月、日

实现了如下功能：

1. 年月日的增加、减少：2017年10月1日加上100个月30天是2025年5月31日
2. 输出某天是星期几：2017年10月1日是星期日
3. 判断某一年是否是闰年：2020年是闰年
4. 下一个工作日（周末）日期：2010年10月2日下一个周末是10月8日

 class Date
 {
   public:
     Date();
     Date(int yy, Month mm, int dd);
     int day() const { return m_day; }
     int year() const { return m_year; }
     Month month() const { return m_month; }

     void add_day(int dd);//增加或减少天数
     void add_month(int mm);//增加或减少月份
     void add_year(int yy);//增加或减少年份

   private:
     int m_year;
     Month m_month;
     int m_day;
 };
 //判断日期是否合法
 bool is_date(int y, Month m, int d);
 //判断是否为闰年
 bool leapyear(int y);
 //两个Date是否相等
 bool operator==(const Date &a, const Date &b);
 bool operator!=(const Date &a, const Date &b);
 //Date输入输出
 ostream &operator<<(ostream &os, const Date &d);
 istream &operator>>(istream &is, Date &dd);
 //今天是星期几
 Day day_of_week(const Date &date);
 ostream &operator<<(ostream &os, const Day &d);
 //下一个周末
 Date next_Sunday(const Date &d);
 //下一个工作日
 Date next_weekday(const Date &d);

具体的实现代码如下：

 #include <iostream>
 #include <vector>
 #include <string>

 using std::istream;
 using std::ostream;
 using std::vector;
 using std::ios_base;
 using std::string;

 namespace Chrono
 {
 class InvalidDate
 {
   public:
     std::string what() { return "InValid Date Occured"; };
 };

 enum class Month
 {
     jan = , //January
     feb,     //February
     mar,     //March
     apr,     //April
     may,     //May
     jun,     //June
     jul,     //July
     aug,     //August
     sep,     //September
     oct,     //October
     nov,     //November
     dec      //December
 };

 enum class Day
 {
     sun, //sunday
     mon, //monday
     tue, //tuesday
     wed, //wednesday
     thu, // thursday
     fri, //friday
     sat  //saturday
 };

 class Date
 {
   public:
     Date();
     Date(int yy, Month mm, int dd);
     int day() const { return m_day; }
     int year() const { return m_year; }
     Month month() const { return m_month; }

     void add_day(int dd);
     void add_month(int mm);
     void add_year(int yy);

   private:
     int m_year;
     Month m_month;
     int m_day;
 };

 bool is_date(int y, Month m, int d);
 bool leapyear(int y);
 bool operator==(const Date &a, const Date &b);
 bool operator!=(const Date &a, const Date &b);
 ostream &operator<<(ostream &os, const Date &d);
 istream &operator>>(istream &is, Date &dd);
 Day day_of_week(const Date &date);
 ostream &operator<<(ostream &os, const Day &d);

 Date next_Sunday(const Date &d);
 Date next_weekday(const Date &d);

 ////////////////////////////////////////////////////////////////////////////////
 //Implements                                                               /////
 ////////////////////////////////////////////////////////////////////////////////
 Date::Date(int yy, Month mm, int dd) : m_year(yy), m_month(mm), m_day(dd)
 {
     if (!is_date(yy, mm, dd))
         throw InvalidDate{};
 }

 const Date &default_date()
 {
     static const Date d{, Month::jan, };
     return d;
 }

 Date::Date() : m_year(default_date().year()),
                m_month(default_date().month()),
                m_day(default_date().day()) {}

 void Date::add_day(int dd)
 {
     if (dd > )
     {
         for (; dd > ; --dd)
         {
             int temp_d = m_day + ;
             switch (month())
             {
             case Month::feb:
                 if ((leapyear(m_year) && temp_d > ) || (!leapyear(m_year) && temp_d > ))
                 {
                     temp_d = ;
                     m_month = Month::mar;
                 }
                 break;
             case Month::apr:
             case Month::jun:
             case Month::sep:
             case Month::nov:
                 if (temp_d > )
                 {
                     temp_d = ;
                     m_month = Month((int)m_month + );
                 }
                 break;
             case Month::dec:
                 if (temp_d > )
                 {
                     temp_d = ;
                     m_month = Month::jan;
                     m_year += ;
                 }
                 break;
             default:
                 if (temp_d > )
                 {
                     temp_d = ;
                     m_month = Month((int)m_month + );
                 }
                 break;
             }
             m_day = temp_d;
         }
     }
     else if (dd < )
     {
         for (; dd < ; ++dd)
         {
             int temp_d = day() - ;
             if (temp_d <= )
             {
                 switch (month())
                 {
                 case Month::jan:
                     m_month = Month::dec;
                     temp_d = ;
                     m_year -= ;
                     break;
                 case Month::mar:
                     m_month = Month::feb;
                     if (leapyear(m_year))
                         temp_d = ;
                     else
                         temp_d = ;
                     break;
                 case Month::feb:
                 case Month::apr:
                 case Month::jun:
                 case Month::oct:
                 case Month::sep:
                 case Month::nov:
                     temp_d = ;
                     m_month = Month((int)m_month - );
                     break;
                 default:
                     temp_d = ;
                     m_month = Month((int)m_month - );
                     break;
                 }
             }
             m_day = temp_d;
         }
     }
 }

 void Date::add_month(int month)
 {
     int temp_y = month /  + m_year;
     int temp_m = month %  + (int)m_day;

     if (temp_y <= )
     {
         temp_y--;
         temp_m = temp_m + ;
     }
     else if (temp_m > )
     {
         temp_y++;
         temp_m = temp_m - ;
     }
     m_year = temp_y;
     m_month = Month(temp_m);
     switch (m_month)
     {
     case Month::feb:
         if (leapyear(m_year) && m_day > )
             m_day = ;
         else if (!leapyear(m_year) && m_day > )
             m_day = ;
         break;
     case Month::apr:
     case Month::jun:
     case Month::sep:
     case Month::nov:
         if (m_day > )
             m_day = ;
     default:
         break;
     }
 }

 void Date::add_year(int n)
 {
     if (month() == Month::feb && day() ==  && !leapyear(m_year + n))
         m_day = ;
     m_year += n;
 }

 bool is_date(int y, Month m, int d)
 {
     if (d <= )
         return false;
     if (m < Month::jan || m > Month::dec)
         return false;
     int days_in_month;
     switch (m)
     {
     case Month::feb:
         days_in_month = leapyear(y) ?  : ;
         break;
     case Month::apr:
     case Month::jun:
     case Month::sep:
     case Month::nov:
         days_in_month = ;
         break;
     default:
         days_in_month = ;
         break;
     }
     if (days_in_month < d)
         return false;
     return true;
 }

 // https://en.wikipedia.org/wiki/Leap_year#Algorithm
 bool leapyear(int y)
 {
     if (y %  != )
         return false;
     else if (y %  != )
         return true;
     else if (y %  != )
         return false;
     return true;
 }
 bool operator==(const Date &a, const Date &b)
 {
     return a.year() == b.year() && a.month() == b.month() && a.day() == b.day();
 }

 bool operator!=(const Date &a, const Date &b)
 {
     return !(a == b);
 }

 ostream &operator<<(ostream &os, const Date &d)
 {
     return os << '(' << d.year()
               << ',' << (int)d.month()
               << ',' << d.day() << ')';
 }

 ostream &operator<<(ostream &os, const Day &d)
 {
     vector<string> weekdays{"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
     os << weekdays[(int)d];
     return os;
 }

 // format (2017,5,23)
 istream &operator>>(istream &is, Date &d)
 {
     int yy, mm, dd;
     char ch1, ch2, ch3, ch4;
     is >> ch1 >> yy >> ch2 >> mm >> ch3 >> dd >> ch4;
     if (!is)
         return is;
     if (ch1 != '(' || ch2 != ',' || ch3 != ',' || ch4 != ')')
         is.clear(ios_base::failbit);
     d = Date{yy, Month(mm), dd};
     return is;
 }

 // https://cs.uwaterloo.ca/~alopez-o/math-faq/node73.html
 Day day_of_week(const Date &date)
 {
     int y = date.year();
     int m = (int)date.month();
     int d = date.day();
     y -= m < ;
     int day_of_week = (y + y /  - y /  + y /  + "-bed=pen+mad."[m] + d) % ;
     return Day(day_of_week);
 }
 Date next_Sunday(const Date &d)
 {
     Date d1 = d;
     while (day_of_week(d1) != Day::sun)
     {
         d1.add_day();
     }
     return d1;
 }

 Date next_weekday(const Date &d)
 {
     Date d1 = d;
     if (day_of_week(d1) == Day::sat)
         d1.add_day();
     else if (day_of_week(d1) == Day::fri)
         d1.add_day();
     else
         d1.add_day();
     return d1;
 }
 }

代码实现