C++|运算符重载（3）|日期类的计算-阿里云开发者社区

前面准备

日期的运算需要考虑到每个月天数不一样，平年闰年2月天数也不一样，因此需要先写两个函数

1.判断year是否为闰年

2.返回当前年月的天数

代码如下

bool leap(int year)
{
  //不是百年4年一闰
  if (year % 100 != 0 && year % 4 == 0)
    return true;
  if (year % 100 == 0 && year % 400 == 0)
    return true;
  return false;
}
 
 
//每月多少天
int MonthDay(int year, int month)
{
  int arr[13] = { 0,31,29,31,30,31,30,31,31,30,31,30,31 };
  if (month == 2 && !leap(year))
    return arr[month]-1;
  else 
    return arr[month];
}

实现功能：

-（分为Date类和Date类相减，Date类和int 相减），+，+=，-=，==,!=,<,<=,>,>=,++,--。

-运算符

这里实现Date类和Date类相减，Date类和int 相减

Date类和int 相减

Date类和int相减，也就是要知道当前日期下几天前的日期，结果是要日期，因此函数的返回类型就是Date，另外-运算符是一个双目运算符，因此运算符重载函数的形参列表只能写一个形参（成员函数有一个默认的this指针），代码如下：

Date operator-(int day)
{
  day -= Day;
  Month--;
  while (day > MonthDay(Year, Day))
  {
    day -= MonthDay(Year, Month);
    Month--;
    if (Month < 1)
    {
      Year--;
      Month = 12;
    }
  }
  Day = MonthDay(Year, Month) - day;
  return *this;
}

Date类和Date类相减

这里我用的是分别算出date1和date2到1年1月1日的天数，然后相减得到两个日期相差的天数，结果是一个天数，那么函数类型就是int,先写日期到1年1月1日天数的函数，代码如下：

int number1()
{
  int year = 1,month = 1;
  int thisday = 0;
  while (year < Year)
  {
    thisday += (leap(year)) ? 366 : 365;
    year++;
  }
 
  while (month < Month)
  {
    thisday += MonthDay(Year, month);
    month++;
  }
  thisday += Day;
  return thisday;
}

接下来是Date类和Date相减的函数

1. int operator-(Date date)
2. {
3.  return this->number1()-date.number1();
4. }

+运算符

这里实现的是，Date类和int相加的结果，也就是，在当前日期下，几天后是几月几号，从这就可以看出运算后的结果是一个Date类，因此函数的类型也就是Date.在函数体刚开始我判断了day是否小于0，小于0也就是几天前是几月几号，直接调用-运算符重载函数就可以。

Date operator+(int day)
{
  if (day < 0)
  {
    return operator-(day);
    
  }
    day += Day;
  while (day > MonthDay(Year, Month))
  {
    day -= MonthDay(Year, Month);
    Month++;
    if (Month > 12)
    {
      Year++;
      Month = 1;
    }
  }
  Day = day;
 
  return *this;
}

+=，-=运算符

+=运算符可以直接调用+运算符重载函数实现

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

同理-=也是同样的道理

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

==,!=运算符

==是判断左右两边的表达式是否相等，Date要相等，就得年相等，月相等，日相等，同时满足，才返回true,代码如下，

bool operator==(Date date)
{
  if(Year == date.Year&&Month==date.Month&&Day==date.Day)return true;
  return false;
}

!=就容易判断了，==的反面就是!= ;

bool operator!=(Date date)
{
  if (*this == date)return false;
  return true;
}

>,>=运算符

在我们的认知里，先出现的日期会大，因此比较的时候数值越小，日期越大，逐一比较就行，具体代码如下：

bool operator>(Date date)
{
  if (Year < date.Year)
    return true;
  else
  {
    if (Month < date.Month)
      return true;
    else
    {
      if (Day < date.Day)
        return true;
      else false;
    }
  }
}

>=,就是既满足大于也满足相等，满足其一即可，具体代码如下

bool operator>=(Date date)
{
  if (*this > date||*this == date)
    return true;
  else
    return false;
}

<,<=运算符

与前面同理，在写<的时候，可以借助前面的>=的函数，>=的反面就是<,具体代码如下：

bool operator<(Date date)
{
  if (*this >= date )return false;
  return true;
}

<=的反面是>,因此可以借助>,来实现<=的重载

bool operator<=(Date date)
{
  if (*this > date)return false;
  else return true;
 
}

++，--运算符

自增，自减运算符就是对自身进行加1，减1的操作，返回自身，需要注意的就是进位，例如：若是Month加到13，那么应该，Year++;Month=1;具体代码如下：

Date operator++()
{
  Day++;
  if (Day > MonthDay(Year, Month))
  {
    Month++;
    if (Month > 12)
    {
      Year++;
      Month = 1;
    }
    Day = 1;
  }
  
  return *this;
}
 
Date operator--()
{
  if (Day == 1)
  {
    Month--;
    if (Month == 0)
    {
      Year--;
      Month = 12;
    }
    Day = MonthDay(Year, Month);
    return *this;
  }
}

功能测试

 
int main()
{
 
 
  cout << "相减：---------------------" << endl;
  Date date2(2024, 1, 9);
  cout << "date2:";
  date2.DatePrint();
  Date date3 = date2 - 679;
  cout << "date2-679=" ;
  date3.DatePrint();
 
  cout <<endl<< "相差：------------------------------------" << endl;
  cout << "date4:";
  Date date4(2023, 9, 9);
  date4.DatePrint();
  cout << "date5:";
  Date date5(2009, 4, 5);
  date5.DatePrint();
  cout << "date5-date4="<< date5 - date4 << endl;
 
  cout << endl<<"相加：----------------------------------" << endl;
 
  Date date(2024, 1, 9);
  cout << "date:";
  date.DatePrint();
  Date date1 = date + 2000;
  cout << "date+2000=";
  date1.DatePrint();
 
  cout <<endl<< "+= ---------------------------" << endl;
  Date date6(2024, 1, 9);
  cout << "date6:";
  date6.DatePrint();
  date6 += 138;
  cout << "date6 += 138:";
  date6.DatePrint();
 
  cout << endl<<"-=-----------------------------" << endl;
  Date date7(2024, 1, 9);
  cout << "date7:";
  date7.DatePrint();
  date7 -= 138;
  cout << "date7-=138:";
  date7.DatePrint();
 
 
 
  cout << endl<<"==------------------------------" << endl;
  Date date8(2024, 1, 9);
  cout << "date8:";
  date8.DatePrint();
  Date date9(2024, 1, 9);
  cout << "date9:";
  date9.DatePrint();
  cout << "date8==date9:" << (date8 == date9) << endl;
 
  cout << endl<<"!=------------------------------------" << endl;
  Date date10(2024, 1, 9);
  cout << "date10:";
  date10.DatePrint();
  Date date11(2024, 1, 10);
  cout << "date11:";
  date11.DatePrint();
  cout << "date10!=date11:" << (date10 != date11) << endl;
 
  cout << endl<<">----------------------------------------" << endl;
  Date date12(2024, 1, 9);
  cout << "date12:";
  date12.DatePrint();
 
  Date date13(2024, 1, 10);
  cout << "date13:";
  date13.DatePrint();
  cout << "date10>date11:" << (date10 > date11) << endl;
 
  cout <<endl<< "++------------------------------" << endl;
  Date date14(2024, 1, 31);
  cout << "date14:";
  date14.DatePrint();
  ++date14;
  cout << "++date14:";
  date14.DatePrint();
 
 
  cout <<endl<< "--              --------------------------" << endl;
  Date date15(2024, 1, 1);
  cout << "date15:";
  date15.DatePrint();
  --date15;
  cout << "--date15:";
  date15.DatePrint();
 
 
 
 
  return 0;
 
}

结果：

完整代码

Date.h

#include<iostream>
#include<stdbool.h>
using namespace std;
bool leap(int year);
int MonthDay(int year, int month);
 
//闰年
 
class Date
{
private:
  int Year;
  int Month;
  int Day;
public:
  //构造函数
  Date();
  Date(int year,int month,int day);
  void DatePrint();
  //加法
  Date operator+(int day);
  //减法
  Date operator-(int day);
  //当前日期到1年1月1日的天数
  int number1();
  //相差
  int operator-(Date date);
  //判断相等
  bool operator==(Date date);
  //判断不相等
  bool operator!=(Date date);
  //实现-=
  Date operator-=(int day);
  //实现+=
  Date operator+=(int day);
  //判断>
  bool operator>(Date date);
  //判断<
  bool operator<(Date date);
  //判断>=
  bool operator<=(Date date);
  //判断>=
  bool operator>=(Date date);
  //++
  Date operator++();
  //--
  Date operator--();
};

fun.cpp

#include"Date.h"
bool leap(int year)
{
  //不是百年4年一闰
  if (year % 100 != 0 && year % 4 == 0)
    return true;
  if (year % 100 == 0 && year % 400 == 0)
    return true;
  return false;
}
 
 
//每月多少天
int MonthDay(int year, int month)
{
  int arr[13] = { 0,31,29,31,30,31,30,31,31,30,31,30,31 };
  if (month == 2 && !leap(year))
    return arr[month]-1;
  else 
    return arr[month];
}
 
Date::Date(int year, int month, int day)
{
  Year = year;
  Month = month;
  Day = day;
}
void Date::DatePrint()
{
  cout << Year << "/" << Month << "/" << Day << endl;
}
 
Date::Date()
{
  Year = 1;
  Month = 1;
  Day = 1;
}
 
 
 
Date Date::operator-(int day)
{
  day -= Day;
  Month--;
  while (day > MonthDay(Year, Day))
  {
    day -= MonthDay(Year, Month);
    Month--;
    if (Month < 1)
    {
      Year--;
      Month = 12;
    }
  }
  Day = MonthDay(Year, Month) - day;
  return *this;
}
 
Date Date::operator+(int day)
{
  if (day < 0)
  {
    return operator-(day);
    
  }
    day += Day;
  while (day > MonthDay(Year, Month))
  {
    day -= MonthDay(Year, Month);
    Month++;
    if (Month > 12)
    {
      Year++;
      Month = 1;
    }
  }
  Day = day;
 
  return *this;
}
 
int Date:: number1()
{
  int year = 1,month = 1;
  int thisday = 0;
  while (year < Year)
  {
    thisday += (leap(year)) ? 366 : 365;
    year++;
  }
 
  while (month < Month)
  {
    thisday += MonthDay(Year, month);
    month++;
  }
  thisday += Day;
  return thisday;
}
 
int Date::operator-(Date date)
{
  return this->number1()-date.number1();
}
 
 
bool Date::operator==(Date date)
{
  if(Year == date.Year&&Month==date.Month&&Day==date.Day)return true;
  return false;
}
 
bool Date::operator!=(Date date)
{
  if (*this == date)return false;
  return true;
}
 
 
Date Date::operator-=(int day)
{
  *this = *this - day;
  return *this;
}
 
Date Date::operator+=(int day)
{
  *this = *this + day;
  return *this;
}
 
bool Date::operator>(Date date)
{
  if (Year < date.Year)
    return true;
  else
  {
    if (Month < date.Month)
      return true;
    else
    {
      if (Day < date.Day)
        return true;
      else false;
    }
  }
}
bool Date::operator>=(Date date)
{
  if (*this > date||*this == date)
    return true;
  else
    return false;
}
 
bool Date::operator<(Date date)
{
  if (*this >= date )return false;
  return true;
}
 
bool Date::operator<=(Date date)
{
  if (*this > date)return false;
  else return true;
 
}
 
 
 
Date Date::operator++()
{
  Day++;
  if (Day > MonthDay(Year, Month))
  {
    Month++;
    if (Month > 12)
    {
      Year++;
      Month = 1;
    }
    Day = 1;
  }
  
  return *this;
}
 
Date Date::operator--()
{
  if (Day == 1)
  {
    Month--;
    if (Month == 0)
    {
      Year--;
      Month = 12;
    }
    Day = MonthDay(Year, Month);
    return *this;
  }
}

test.cpp

#include"Date.h"
int main()
{
 
 
  cout << "相减：---------------------" << endl;
  Date date2(2024, 1, 9);
  cout << "date2:";
  date2.DatePrint();
  Date date3 = date2 - 679;
  cout << "date2-679=" ;
  date3.DatePrint();
 
  cout <<endl<< "相差：------------------------------------" << endl;
  cout << "date4:";
  Date date4(2023, 9, 9);
  date4.DatePrint();
  cout << "date5:";
  Date date5(2009, 4, 5);
  date5.DatePrint();
  cout << "date5-date4="<< date5 - date4 << endl;
 
  cout << endl<<"相加：----------------------------------" << endl;
 
  Date date(2024, 1, 9);
  cout << "date:";
  date.DatePrint();
  Date date1 = date + 2000;
  cout << "date+2000=";
  date1.DatePrint();
 
  cout <<endl<< "+= ---------------------------" << endl;
  Date date6(2024, 1, 9);
  cout << "date6:";
  date6.DatePrint();
  date6 += 138;
  cout << "date6 += 138:";
  date6.DatePrint();
 
  cout << endl<<"-=-----------------------------" << endl;
  Date date7(2024, 1, 9);
  cout << "date7:";
  date7.DatePrint();
  date7 -= 138;
  cout << "date7-=138:";
  date7.DatePrint();
 
 
 
  cout << endl<<"==------------------------------" << endl;
  Date date8(2024, 1, 9);
  cout << "date8:";
  date8.DatePrint();
  Date date9(2024, 1, 9);
  cout << "date9:";
  date9.DatePrint();
  cout << "date8==date9:" << (date8 == date9) << endl;
 
  cout << endl<<"!=------------------------------------" << endl;
  Date date10(2024, 1, 9);
  cout << "date10:";
  date10.DatePrint();
  Date date11(2024, 1, 10);
  cout << "date11:";
  date11.DatePrint();
  cout << "date10!=date11:" << (date10 != date11) << endl;
 
  cout << endl<<">----------------------------------------" << endl;
  Date date12(2024, 1, 9);
  cout << "date12:";
  date12.DatePrint();
 
  Date date13(2024, 1, 10);
  cout << "date13:";
  date13.DatePrint();
  cout << "date10>date11:" << (date10 > date11) << endl;
 
  cout <<endl<< "++------------------------------" << endl;
  Date date14(2024, 1, 31);
  cout << "date14:";
  date14.DatePrint();
  ++date14;
  cout << "++date14:";
  date14.DatePrint();
 
 
  cout <<endl<< "--              --------------------------" << endl;
  Date date15(2024, 1, 1);
  cout << "date15:";
  date15.DatePrint();
  --date15;
  cout << "--date15:";
  date15.DatePrint();
 
 
 
 
  return 0;
 
}

C++|运算符重载（3）|日期类的计算