用c++编写复数类的友元函数的双目运算符重载代码

下面是一个用 C++ 编写的复数类，包含了友元函数的双目运算符重载代码：

#include<iostream>
using namespace std;

class Complex {
private:
    double real;
    double imag;
public:
    Complex(double r = 0, double i = 0) {
        real = r;
        imag = i;
    }
    friend Complex operator+ (Complex const &, Complex const &);
    friend Complex operator- (Complex const &, Complex const &);
    friend Complex operator* (Complex const &, Complex const &);
    friend Complex operator/ (Complex const &, Complex const &);
    void print() {
        cout << real << " + i" << imag << endl;
    }
};

Complex operator+ (Complex const &c1, Complex const &c2) {
    return Complex(c1.real + c2.real, c1.imag + c2.imag);
}

Complex operator- (Complex const &c1, Complex const &c2) {
    return Complex(c1.real - c2.real, c1.imag - c2.imag);
}

Complex operator* (Complex const &c1, Complex const &c2) {
    return Complex(c1.real*c2.real - c1.imag*c2.imag, c1.real*c2.imag + c1.imag*c2.real);
}

Complex operator/ (Complex const &c1, Complex const &c2) {
    double r = c2.real*c2.real + c2.imag*c2.imag;
    return Complex((c1.real*c2.real + c1.imag*c2.imag) / r, (c1.imag*c2.real - c1.real*c2.imag) / r);
}

int main() {
    Complex c1(3, 4), c2(2, 3);
    Complex c3 = c1 + c2;
    Complex c4 = c1 - c2;
    Complex c5 = c1 * c2;
    Complex c6 = c1 / c2;
    c3.print();
    c4.print();
    c5.print();
    c6.print();
    return 0;
}

在上面的代码中，我们使用了 `friend` 关键字来声明双目运算符重载函数为 `Complex` 类的友元函数，从而可以访问 `Complex` 类的私有成员变量 `real` 和 `imag`。同时，我们还重载了加、减、乘、除四种运算符，其中加、减、乘、除的运算结果均为复数。最后，我们在 `main` 函数中测试了这四种运算符的重载效果，输出了运算结果。