源程序：
//1.聲明復數的類，complex，使用友元函數 add 實現復數加法。
#include < iostream >
using namespace std;
class Complex
{
private:
double real, image;
public:
Complex() {}
Complex(double a, double b)
{
real = a;
image = b;
}
void setRI(double a, double b)
{
real = a;
image = b;
}
double getReal()
{
return real;
}
double getImage()
{
return image;
}
void print()
{
if (image>0)
cout << "復數：" << real << " + " << image << "i" << endl;
if (image<0)
cout << "復數：" << real << " - " << image << "i" << endl;
}
friend Complex add(Complex, Complex);//聲明友元函數
};
Complex add(Complex c1, Complex c2)//定義友元函數
{
Complex c3;
c3.real = c1.real + c2.real;//訪問 Complex 類中的私有成員
c3.image = c1.image + c2.image;
return c3;
}
void main()
{
Complex c1(19, 0.864), c2, c3;
c2.setRI(90, 125.012);
c3 = add(c1, c2);
cout << "復數一：";
c1.print();
cout << "復數二：";
c2.print();
cout << "相加后：";
c3.print();
system("pause");
}
運行結果：
