C语言运算符的重载详解

#include<iostream>
using namespace std;
//定义复数类
class Complex
{ 
	public:
		Complex(double x=0.0, double y=0.0);  //构造函数
		Complex(const Complex &c);  //复制构造函数 
		~Complex();  //析构函数
		void display() const;  //复数打印函数
		Complex operator +(const Complex &c) const;  //加法运算符重载
		Complex operator -(const Complex &c) const;  //减法运算符重载 
	private:
		double real;  //实部
		double imag;  //虚部 
}; 
Complex::Complex(double x, double y): real(x), imag(y){}
Complex::~Complex(){}
Complex::Complex(const Complex &c): real(c.real), imag(c.imag){}
void Complex::display() const
{
	cout<<"("<<real<<", "<<imag<<")"<<endl;	
}
Complex Complex::operator +(const Complex &c) const
{
	Complex temp;
	temp.real = real + c.real;
	temp.imag = imag + c.imag;
	return temp;
	/*或者创建一个临时无名对象作为返回值*/
	//return Complex(real+c.real, imag+c.imag); 
}
Complex Complex::operator -(const Complex &c) const
{
	Complex temp;
	temp.real = real - c.real;
	temp.imag = imag - c.imag;
	return temp;
}
int main()
{
	Complex c1(6.7, 4.4);
	Complex c2(3.2, 1.7);
	cout<<"c1 = ";
	c1.display();
	cout<<endl;
	cout<<"c2 = ";
	c2.display();
	cout<<endl;
	Complex c3, c4;
	c3 = c1 + c2;
	c4 = c1 - c2;
	cout<<"c1 + c2 = ";
	c3.display();
	cout<<endl;
	cout<<"c1 - c2 = ";
	c4.display();
	cout<<endl;
	return 0;
} 

#include<iostream>
using namespace std;
class Clock
{
	public:
		Clock(int hour=0, int minute=0, int second=0);
		~Clock();
		void showTime() const;
		Clock& operator ++();  //前置单目运算符重载
		Clock operator ++(int);  //后置单目运算符重载 
	private:
		int hour;
		int minute;
		int second;
};
Clock::Clock(int hour, int minute, int second)
{
	if(0<=hour && hour<24 && 0<=minute && minute<60 && 0<=second && second<60)
	{
		this->hour = hour;
		this->minute = minute;
		this->second = second;
	}
	else
	{
		cout<<"Time error!"<<endl;
	}
}
Clock::~Clock(){}
void Clock::showTime() const
{
	cout<<hour<<":"<<minute<<":"<<second<<endl;
}
Clock& Clock::operator ++()  //函数返回值是对象的引用是为了更高效（减少临时对象的生成）
{
	second++;
	if(second >= 60)
	{
		second %= 60;
		minute++;
		if(minute >= 60)
		{
			minute %= 60;
			hour = (hour + 1) % 24;
		}
	}
	return *this;
}
Clock Clock::operator ++(int)  //注意形参表中的整型参数
{
	Clock old = *this;
	++(*this);   //调用前置“++”运算符
	/*也可以写具体： 
	second++;
	if(second >= 60)
	{
		second %= 60;
		minute++;
		if(minute >= 60)
		{
			minuet %= 60;
			hour = (hour + 1) % 24;
		}
	}
	*/
	return old; 
} 
int main()
{
	Clock myClock(23, 59, 59); 
 	cout << "First time output: "; 
 	myClock.showTime(); 
 	cout << "Show myClock++: "; 
 	(myClock++).showTime(); 
 	cout << "Show ++myClock: "; 
 	(++myClock).showTime();
	return 0;
}

#include<iostream>
using namespace std;
class Complex
{
	public:
		Complex(double x=0.0, double y=0.0);
		~Complex();
		friend Complex operator +(const Complex &c1, const Complex &c2);  //声明为类的友元
		friend Complex operator -(const Complex &c1, const Complex &c2);
		friend ostream& operator <<(ostream &out, const Complex &c);
	private:
		double real;
		double imag;
};
Complex::Complex(double x, double y): real(x), imag(y){}
Complex::~Complex(){}
Complex operator +(const Complex &c1, const Complex &c2)
{
	Complex temp;
	temp.real = c1.real + c2.real;
	temp.imag = c1.imag + c2.imag; 
	return temp;
	/*或者创建一个临时无名对象作为返回值*/
	//return Complex(c1.real+c2.real, c1.imag+c2.imag); 
} 
Complex operator -(const Complex &c1, const Complex &c2)
{
	return Complex(c1.real-c2.real, c1.imag-c2.imag);
}
ostream& operator <<(ostream& out, const Complex &c)
{
	out<<"("<<c.real<<", "<<c.imag<<")";
	return out;
}
/*若输出为复数的标准形式：
在复数两端加上括号，实部和虚部均保留两位小数，
如(8.23+2.00i)、(7.45-3.40i)*/
/*
ostream& operator <<(ostream& out, const Complex &c)
{
    if(c.imag>0)
        out<<setiosflags(ios::fixed)<<setprecision(2)<<"("<<c.real<<"+"<<c.imag<<"i)"<<endl;
    else
        out<<setiosflags(ios::fixed)<<setprecision(2)<<"("<<c.real<<c.imag<<"i)"<<endl;
    return out;
}
*/
int main()
{
	Complex c1(5, 4), c2(2, 10), c3; 
 	cout << "c1 = " << c1 << endl; 
 	cout << "c2 = " << c2 << endl; 
 	c3 = c1 - c2;   //使用重载运算符完成复数减法 
 	cout << "c3 = c1 - c2 = " << c3 << endl; 
 	c3 = c1 + c2;   //使用重载运算符完成复数加法 
 	cout << "c3 = c1 + c2 = " << c3 << endl;
	return 0;
}