【C++】实现Date类的各种运算符重载

上一篇文章只实现了operator==操作符重载，由于运算符较多，该篇文章单独实现剩余所有的运算符重载。继续以Date类为例，实现运算符重载：
1.Date.h

#pragma once
 
#include <iostream>
#include <assert.h>

using namespace std;

class Date
{
   
private:
	int _year;
	int _month;
	int _day;
public:
	void Print();
	Date(int yaer, int month, int day);

	bool operator<(const Date& d);
	bool operator<=(const Date& d);
	bool operator>(const Date& d);
	bool operator>=(const Date& d);
	bool operator==(const Date& d);
	bool operator!=(const Date& d);

//单独的用一个函数把每个月多少天，封装起来
	int GetMonthDays(int year, int month)
	{
   
		assert(month > 0 && month < 13);

		static int MonthDay[13] = {
    0,31,28,31,30,31,30,31,31,30,31,30,31 };
		if (month==2&&(year % 4 == 0 && year % 100 != 0))
		{
   
			return 29;
		}
		return MonthDay[month];
	}

	Date& operator+=(int day);
	Date operator+(int day);

	Date& operator-=(int day);
	Date operator-(int day);
	//++d，前置++
	Date& operator++();
	//d++，后置++
	Date operator++(int);
	//前置--
	Date& operator--();
	//后置--
	Date operator--(int);

	//两个日期相减：d1-d2
	int operator-(const Date& d);
};

Date.cpp

#define _CRT_SECURE_NO_WARNINGS 1 
#include <stdio.h>

#include "Date.h"

void Date::Print()
{
   
	cout << _year << "/" << _month << "/" << _day << endl;
}

Date::Date(int year=1, int month=1, int day=1)
{
   
	_year = year;
	_month = month;
	_day = day;
}
//   写好一个直接复用！！！
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) && (_day < d._day))
			return true;
		else
			return false;
	}
	else
		return false;
}

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

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);
}

Date& Date::operator+=(int day)
{
   
	_day += day;//先加
	//这里是while,因为如果是if的话，如果一次加了很大的数据减一次不一定能减得完!!!
	while(_day > GetMonthDays(_year, _month))
	{
   
		_day -= GetMonthDays(_year, _month);
		++_month;
		if (_month == 13)
		{
   
			++_year;
			_month = 1;
		}
	}
	return *this;
}

Date Date::operator+(int day)
{
   
	Date tmp=*this;

   
	tmp += day;
	return tmp;
}


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


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

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

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

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

Date Date::operator--(int)
{
   
	Date tmp = *this;
	*this -= 1;
	return tmp;
}
//日期-日期，计算两个日期之间相差多少天

int Date::operator-(const Date& d)
{
   
	int flag = 1;
	Date max = *this;
	Date min = d;

	if (*this < d)
	{
   
		//赋值为-1的原因：因为这个函数是有顺序的d1-d2，如果遇到d1<d2，也就是小减大，最终返回的结果是个负数，所以说这里要变成-1。
		flag = -1;
		max = d;
		min = *this;
	}
	//定义一个变量
	int n = 0;
	// 用循环算两个日期中间的差值
	while (min != max)
	{
   
		++min;
		++n;
	}

	return n * flag;
}

3.Test.cpp

#define _CRT_SECURE_NO_WARNINGS 1 
#include <stdio.h>
#include "Date.h"

int main()
{
   
	Date d1(2024, 2, 15);

	Date d2 = d1 + 20;
	d1.Print();
	d2.Print();

	bool ret=d1 > d2;
	if (ret)
	{
   
		d1.Print();
	}

	d2 += 100;
	d2.Print();


	d2 -= 100;
	d2.Print();
	Date d3 = d2 - 10;
	d3.Print();

	Date d4(2024, 1, 29);
	Date d5(2024, 8, 1);
	cout << d5 - d4 << endl;

	++d5;
	d5.Print();

	d5++;
	d5.Print();

	--d5;
	d5.Print();

	d5--;
	d5.Print();
	return 0;
}