C++ 日期类函数 完善

#include<iostream>using namespace std;class Date{public:friend ostream& operator<<(ostream& _cout,const Date& d)//友元函数，取ostream的引用使返回值连续输出{_cout<<d._year<<"-"<<d._month<<"-"<<d._day<<endl;return _cout;}Date(int year = 1990,int month = 1,int day = 1)//构造函数:_year(year),_month(month),_day(day){if(!(_year > 0&&(_month > 0&&_month < 13)&&(_day > 0&&_day <= _GetMonthDays(_year,_month))))//判断非法日期{_year = 1990;_month = 1;_day = 1;    //恢复默认值}}Date(const Date& d)//拷贝构造函数，不需判断日期是否非法，在构造函数已经判断过{_year = d._year;_month = d._month;_day = d._day;}Date& operator=(const Date& d)//赋值运算符重载必须返回一个对象{if(this != &d)//判断是否自己给自己赋值{_year = d._year;    _month = d._month;    _day = d._day;}return *this;//返回当前对象（返回d也可）}Date& operator++()//前置加加，返回引用{*this = *this + 1;return *this;}Date& operator--(){*this = *this - 1;return *this;}Date operator++(int)//后置加加，传参int区分前置加加,返回值不传引用{Date temp(*this);*this = *this + 1;return temp;}Date operator--(int){Date temp(*this);*this = *this - 1;return temp;} Date operator+(int days){if(days < 0)//加负天数{return *this - (0 - days);//返回Date operator-(int days)函数}Date temp(*this);//将*this值保存到临时变量temp中int daysInMonth = 0;//用于接收_GetMonthDays(temp._year,temp._month）函数的值temp._day += days;while(temp._day > daysInMonth == _GetMonthDays(temp._year,temp._month))//{if(temp._month == 12)//如果为十二月则年份加1{temp._year += 1;temp._month = 1;}elsetemp._month += 1;//月份加一temp._day = temp._day - _GetMonthDays(temp._year,temp._month);//加法运算后的天数减去这个月的天数}return temp;}Date operator-(int days){if(days<0){return *this + (0 - days);//返回Date operator+(int days)函数}Date temp(*this);int daysInMonth = 0;temp._day -= days;while(temp._day <= 0)//减去days后若小于0则一直循环{if(temp._month = 1){temp._year -= 1;temp._month = 12;}elsetemp._month -= 1;temp._day += _GetMonthDays(temp._year,temp._month);//加上上一个月的天数}return temp;}int operator-(Date& d){Date minDate(*this);Date maxDate(d);if(minDate > maxDate){minDate = maxDate;maxDate = *this;}size_t count = 0;while(minDate < maxDate){++minDate;++count;}return count;}bool operator>(Date& d){if(_year>d._year||(_year == d._year && _month>d._month)||(_year == d._year && _month == d._month && _day>d._day))return true;return false;}bool operator==(Date& d){if(_year == d._year && _month == d._month && _day == d._day)return true;return false;}bool operator!=(Date& d){return !(*this == d);}bool operator<(Date& d){return !(*this>d || *this==d);//不是大于或等于}private:int _GetMonthDays(int year,int month)//获取每个月的最大天数函数{int daysInMonth[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};//定义一个存放每个月天数（非闰年）的数组if(2 == month&&Isleap(_year)){daysInMonth[month] += 1;}return daysInMonth[month];}bool Isleap(int year)const//判断闰年{if((0 == year%4&&0 != year%100)||0 == year%400){return true;}return false;}private:int _year;int _month;int _day;};int main(){Date d1(2017,3,4);Date d2(2017,2,13);cout<<d1++<<endl;system("pause");return 0;}