C++类与对象之日期类的实现

#include<iOStream>

using std::cout;
using std::endl;
using std::cin;

class Date
{

public:
//构造函数
 Date(int year = 0, int month = 1, int day = 1)
 {
  if (year >= 0 && month > 0 && month<13 && day>0 && day <= GetMonthDay(year, month))
  {
   _year = year;
   _month = month;
   _day = day;
  }
  else
  {
   cout << "输入日期不和法" << endl;
  }
 }
//拷贝构造
 Date(const Date& d)
 {
  _year = d._year;
  _month = d._month;
  _day = d._day;
 }
//赋值运算符
 Date& operator=(const Date&d)
 {
  if (this != &d)
  {
   _year = d._year;
   _month = d._month;
   _day = d._day;
  }
  return *this;
 }
 //判断合法性
 int GetMonthDay(int year, int month);
 //输出日期
 void prit();
 //日期+=
 Date& operator+=(int day);
 //日期+
 Date operator+(int day);
 //日期-=
 Date& operator-=(int day);
 //日期-
 Date operator-(int day);
 //日期==
 bool operator==(const Date& d);
 //日期>
 bool operator>(const Date& d);
 //日期！=
 bool operator != (const Date& d);
 //<
 bool operator < (const Date& d);
 //>=
 inline bool operator >= (const Date& d);
 //<=
 bool operator <= (const Date& d);
 //++d
 Date& operator++();
 //d++
 Date& operator++(int);
 //--d
 Date& operator--();
 //d--
 Date& operator--(int);
 //日期-日期
 int operator-(const Date& d);

private:
 int _year;
 int _month;
 int _day;
};
//给出当年当月的天数
inline int Date::GetMonthDay(int year, int month)
{
 static int dayArray[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
 dayArray[2] = 28;
 if (month == 2 && ((year % 4 == 0) && (year % 100 != 0)) || year % 400 == 0)
 {
  dayArray[2] = 29;
 }
 return dayArray[month];
}

Date& Date::operator+=(int day)
{
 if (day > 0)
 {
  _day += day;
  while (_day > GetMonthDay(_year, _month))
  {
   _day -= GetMonthDay(_year, _month);
   _month++;
   if (_month > 12)
   {
    _year++;
    _month = 1;
   }
  }
 }
 else
 {
  *this -= (-day);
 }

 return *this;
}

Date& Date::operator-=(int day)
{
 if (day > 0)
 {
  _day -= day;
  while (_day <= 0)
  {
   _month--;
   _day += GetMonthDay(_year, _month);
   if (_month == 0)
   {
    _year--;
    _month = 12;
   }
  }
 }
 else
 {
  *this += (-day);
 }
 return *this;
}

Date Date::operator-(int day)
{
 Date ret(*this);
 ret -= day;
 return *ret;
}

Date Date::operator+(int day)
{
 Date ret(*this);
 ret += day;
 return ret;
}

Date& Date::operator++()
{
 *this += 1;
 return *this;
}

Date& Date::operator++(int)
{
 Date tmp(*this);
 tmp += 1;
 return *this;
}

Date& Date::operator--()
{
 *this -= 1;
 return *this;
}

Date& Date::operator--(int)
{
 Date tmp(*this);
 tmp -= 1;
 return *this;

bool Date::operator>(const Date& d)
{
 if (_year > d._year)
 {
  return true;
 }
 else if (_year == d._year)
 {
  if (_month > d._month)
  {
   return true;
  }
  else if (_month == d._month)
  {
   if (_day > d._day)
   {
    return true;
   }
  }
 }

 return false;
}

bool Date::operator==(const Date& d)
{
 return _year == d._year
  &&_month == d._month
  &&_day == d._day;

}

bool Date::operator >= (const Date& d)
{
 return (*this > d) || (*this == d);
}

bool Date::operator < (const Date& d)
{
 return !(*this>d);

}

bool Date::operator <= (const Date& d)
{
 return (*this < d) || (*this == d);
}

bool Date::operator != (const Date& d)
{
 return !(*this == d );
}

int Date::operator-(const Date& d)
{
 Date max = *this;
 Date min = d;
 int flag = 1;
 if (max < min)
 {
  max = d;
  min = *this;
  flag = -1;
 }
 int m = 0;
 while (max!=min)
 {
  ++min;
  ++m;
 }

 return m*flag;
}

void Date::prit()
{
 cout << _year << "年" << _month << "月" << _day << "日" << endl;
}