第8周任务2（定义各种重载运算符）

/* (程序头部注释开始)
* 程序的版权和版本声明部分
* Copyright (c) 2011, 烟台大学计算机学院学生 
* All rights reserved.
* 文件名称：                              
* 作    者：   臧鹏               
* 完成日期：   2012   年  4 月 9  日
* 版 本 号：          

* 对任务及求解方法的描述部分
* 输入描述：
* 问题描述：定义各种运算符
* 程序输出： 
* 程序头部的注释结束
*/
#include <iostream>
using namespace std;
class CTime
{
private:
	unsigned short int hour;    // 时
	unsigned short int minute;  // 分
	unsigned short int second;  // 秒
public:
	CTime(int h=0,int m=0,int s=0):hour(h), minute(m), second(s){}  ;
	void setTime(int h,int m,int s);
	void display();
	//比较运算符(二目)的重载
	bool operator > (CTime &t);
	bool operator < (CTime &t);
	bool operator >= (CTime &t);
	bool operator <= (CTime &t);
	bool operator == (CTime &t);
	bool operator != (CTime &t);
	//二目运算符的重载
	CTime operator+(CTime &c);//返回c所规定的时、分、秒后的时间，例t1(8,20,25),t2(11,20,50)，t1+t2为:41:15
	CTime operator-(CTime &c);//对照+理解
	CTime operator+(int s);//返回s秒后的时间
	CTime operator-(int s);//返回s秒前的时间
	//一目运算符的重载
	CTime operator++(int);//后置++，下一秒
	CTime operator++();//前置++，下一秒
	CTime operator--(int);//后置--，前一秒
	CTime operator--();//前置--，前一秒
	//赋值运算符的重载     
	CTime operator+=(CTime &c);
	CTime operator-=(CTime &c);
	CTime operator+=(int s);//返回s秒后的时间
	CTime operator-=(int s);//返回s秒前的时间
};
//下面实现所有的运算符重载代码。
//为简化编程，请注意通过调用已有函数，利用好各函数之间的关系
void CTime::setTime(int h,int m,int s)
{
	hour = h;
	minute = m;
	second = s;
}
void CTime::display()//显示函数
{
	cout<< hour << ":" << minute << ":"  << second << endl;
}

bool CTime::operator > (CTime &t)//大于比较符（把时间都化成秒进行比较要容易得多，下同）
{
	if(hour*3600+minute*60+second >t.hour*3600+t.minute*60+t.second)
	{
		return true;
	}
	else
		return false;
}
bool CTime::operator < (CTime &t)//小于比较符
{
	if(hour*3600+minute*60+second <t.hour*3600+t.minute*60+t.second)
	{
		return true;
	}
	else
		return false;
}
bool CTime::operator >= (CTime &t)//大于等于比较符
{
	if(hour*3600+minute*60+second >= t.hour*3600+t.minute*60+t.second)
	{
		return true;
	}
	else
		return false;
}
bool CTime::operator <= (CTime &t)//小于等于比较符
{
	if(hour*3600+minute*60+second <= t.hour*3600+t.minute*60+t.second)
	{
		return true;
	}
	else
		return false;
}
bool CTime::operator == (CTime &t)//等于比较符
{
	if(hour == t.hour && minute == t.minute && second == t.second)
	{
		return true;
	}
	else
		return false;
}
bool CTime::operator != (CTime &t)//不等于
{
	if(hour != t.hour ||minute != t.minute || second != t.second)
	{
		return true;
	}
	else
		return false;
}
//二目运算符的重载
CTime CTime::operator+(CTime &t)//返回c所规定的时、分、秒后的时间，例t1(8,20,25),t2(11,20,50)，t1+t2为:41:15
{
	CTime t1;
	int time;
	time = hour*3600+minute*60+second+t.hour*3600+t.minute*60+t.second;//利用中间变量，把时间都化成秒在进行运算，再化成时分秒，下同
	t1.hour=time/3600;
	time =time%3600;
	t1.minute =time/60;
	time = time%60;
	t1.second =time;
	return t1;
}

CTime CTime::operator-(CTime &t)//对照+理解
{
	CTime t1;
	int time;
	time = hour*3600+minute*60+second-(t.hour*3600+t.minute*60+t.second);
	if(time<0)
	{
		time = -time;
	}
	t1.hour=time/3600;
	time =time%3600;
	t1.minute =time/60;
	time = time%60;
	t1.second =time;
	return t1;
}
CTime CTime::operator+(int s)//返回s秒后的时间
{
	CTime t0;//利用一个中间变量是防止函数把this指针所指向的这个对象改变，此处不能用const，否则运行函数无效
	int time = hour * 3600 + minute * 60 + second + s; 

	t0.hour = time / 3600; 

	time = time % 3600; 

	t0.minute = time / 60; 

	time = time % 60; 

	t0.second = time;   

	return t0; //返回中间变量，如果返回（*this）则下个函数的默认对象就为这个函数所改变后的对象
}
CTime CTime::operator-(int s)//返回s秒前的时间
{
	CTime t0;

	int time = hour * 3600 + minute * 60 + second-s;   

	t0.hour = time / 3600; 

	time = time % 3600; 

	t0.minute = time / 60; 

	time = time % 60; 

	t0.second = time; 

	return t0; 
}
//一目运算符的重载
CTime CTime::operator++(int)//后置++，下一秒
{
	CTime temp(*this);//提前保存this指针所指向的这个对象
	{
		second++;
		if(second>=60)
		{
			second-=60;
			++minute;
			if(minute>=60)
			{
				minute-=60;
				++hour;
			}
		}

	}
	return temp;//返回的对象为改之前的，但实际对象已经改变了
}
CTime CTime::operator++()//前置++，下一秒
{
	if(++second>=60)
	{
		second-=60;
		++minute;
		if(minute>=60)//注意分钟也可能越界
		{
			minute-=60;
			++hour;
		}
	}
	return (*this);
}
CTime CTime::operator--(int)//后置--，前一秒
{
	CTime temp(*this);
	second--;
	if(second<0)//秒被减成负的那么要考虑分钟减一。秒数为60-second
	{   
		second = 60+second;
		--minute;
		if(minute<0)
		{
			--hour;
		}
	}
	return temp;
}
CTime CTime::operator--()//前置--，前一秒
{
	if(--second<0)
	{
		second =60+second;
		--minute;
		if(minute<0)
		{
			--hour;
		}
	}
	return (*this);
}
//赋值运算符的重载     
CTime CTime::operator+=(CTime &t)
{
	int time;
	time = hour*3600+minute*60+second+t.hour*3600+t.minute*60+t.second;
	hour = time/3600;
	if(hour>=24)//如果小时大于24，自动归零
	{
		hour-=24;
	}
	time = time%3600;
	minute = time/60;
	time = time%60;
	second = time;
	return  (*this);
}
CTime CTime::operator-=(CTime &t)
{
	int time;
	time = hour*3600+minute*60+second-(t.hour*3600+t.minute*60+t.second);
	if (time<0)
	{
		time = -time;
	}
	hour = time/3600;
	if(hour>=24)
	{
		hour-=24;
	}
	time = time%3600;
	minute = time/60;
	time = time%60;
	second = time;
	return  (*this);
}
CTime CTime::operator+=(int s)//返回s秒后的时间
{

	second+=s;
	if(second>=60)
	{
		minute+=second/60;
		second = second%60;
	}
	if(minute>=60)
	{
		hour+=minute/60;
		minute=minute%60;
	}
	if(hour>=24)
	{
		hour = hour%24;
	}
	return  (*this);
}
CTime CTime::operator-=(int s)//返回s秒前的时间
{
	int time;
	time = hour*3600+minute*60+second-s;
	if(time<0)
	{
		time = -time;
	}
	else
		hour = time/3600;
	time = time%3600;
	minute = time/60;
	time = time%60;
	second = time;
	return (*this);
}


void main()
{
	CTime t1(8,20,25),t2(11,20,50),t;
	cout<<"t1为：";
	t1.display();
	cout<<"t2为：";
	t2.display();
	cout<<"下面比较两个时间大小：\n";
	if (t1>t2) cout<<"t1>t2"<<endl;
	if (t1<t2) cout<<"t1<t2"<<endl;
	if (t1==t2) cout<<"t1＝t2"<<endl; 
	if (t1!=t2) cout<<"t1≠t2"<<endl;
	if (t1>=t2) cout<<"t1≥t2"<<endl;
	if (t1<=t2) cout<<"t1≤t2"<<endl;
	cout<<endl;
	//下面自行设计对其他运算符的重载的测试
	t = t1+t2;
	cout<<"t1+t2 =";
	t.display();

	t = t1-t2;
	cout<<"t1-t2 =";
	t.display();

	t = t1+15;
	cout<<"t1+15s =";
	t.display();

	t = t1-15;
	cout<<"t1-15s =";
	t.display();

	t = t1++;
	cout<<"t1++ =";
	t.display();

	t = ++t1;
	cout<<"++t1 =";
	t.display();

	t = t1--;
	cout<<"t1-- =";
	t.display();

	t = --t1;
	cout<<"--t1 =";
	t.display();
	t1+=t2;
	cout<<"t1+=t2  =";
	t1.display();
	t1-=t2;
	cout<<"t1-=t2  =";
	t1.display();
	t1 +=124;
	cout<<"t1+=124s =";
	t1.display();
	t1 -=555;
	cout<<"t1-=555s =";
	t1.display();
	system("pause");


}

经验积累：

每个成员函数都可能改变当前对象的值，所以要想后面的函数不受影响，可以用中间变量的方法，进行运算，返回那个中间变量，这样就使后面的函数不受影响了，再就是对时间的处理上要注意越界的情况，进还是退，要有相关的机制来应对。再就是程序虽长但是要细心和有耐心。