用友元函数重载运算符

// 用友元函数重载运算符
#include<iostream>
using namespace std;


class COMPLEX
{

private:

doublex, y;

public:

COMPLEX(double xx = 0, double yy = 0)

{

x = xx;

y = yy;

}

void display()

{

cout << "(" << x;

if(y > 0)

cout << "+" << y << "*i)";

else if(y < 0)

cout << y << "*i)";

else

cout << ")";

}

// 友元函数声明,重载运算符 *

friend COMPLEX operator * (COMPLEX &c1, COMPLEX &c2);

//friend bool operator == (COMPLEX &c1, COMPLEX &c2);

//为什么下面这个重载声明就不行呢?

//编译出错,说是没有访问私有成员的权限.

//可是该函数已经声明为COMPLEX的友元函数了呀.

//如何是好?

};

// bool operator == (COMPLEX &c1, COMPLEX &c2)

// {

// bool c;

// c = (c1.x == c2.x) && (c1.y == c2.y);

// return c;

// }

// 友元函数实现
COMPLEX operator * (COMPLEX &c1, COMPLEX &c2)
{

doubler = c1.x * c2.x - c1.y * c2.y;
double i = c1.x * c2.y + c1.y * c2.x;// How about c2. x ??
return COMPLEX(r, i);

}
void main()
{

COMPLEXc1(-3, 2), c2(3, -2), c3;
c3 = c1 * c2;
c1.display();
cout << " + ";
c2.display();
cout << " = ";
c3.display();
cout << endl << endl;

}