用类的友元函数，而不是成员函数定义复数类重载运算符+、-、*、/，使之能用于复数的加减乘除

/*
*Copyright (c) 2016,烟台大学计算机学院
*All rights reserved.
*文件名称：main.cpp
*作    者：郭辉
*完成时间：2016年5月23日
*版 本 号：v1.0
*用类的友元函数，而不是成员函数定义复数类重载运算符+、-、*、/，使之能用于复数的加减乘除
*问题描述：
*输入描述：无。
*程序输出：复数的加减乘除。
*/#include <iostream>
using namespace std;
class Complex
{
public:
Complex()
{
real=0;
imag=0;
}
Complex(double r,double i)
{
real=r;
imag=i;
}
friend Complex operator+(Complex &c1, Complex &c2);
friend Complex operator+(double d1, Complex &c2);
friend Complex operator+(Complex &c1, double d2);
friend Complex operator-(Complex &c1, Complex &c2);
friend Complex operator-(double d1, Complex &c2);
friend Complex operator-(Complex &c1, double d2);
friend Complex operator*(Complex &c1, Complex &c2);
friend Complex operator*(double d1, Complex &c2);
friend Complex operator*(Complex &c1, double d2);
friend Complex operator/(Complex &c1, Complex &c2);
friend Complex operator/(double d1, Complex &c2);
friend Complex operator/(Complex &c1, double d2);
void display();
private:
double real;
double imag;
};

//复数相加：(a+bi)+(c+di)=(a+c)+(b+d)i.
Complex operator+(Complex &c1, Complex &c2)
{
Complex c;
c.real=c1.real+c2.real;
c.imag=c1.imag+c2.imag;
return c;
}
Complex operator+(double d1, Complex &c2)
{
Complex c(d1,0);
return c+c2; //按运算法则计算的确可以，但充分利用已经定义好的代码，既省人力，也避免引入新的错误，但可能机器的效率会不佳
}
Complex operator+(Complex &c1, double d2)
{
Complex c(d2,0);
return c1+c;
}
//复数相减：(a+bi)-(c+di)=(a-c)+(b-d)i.
Complex operator-(Complex &c1, Complex &c2)
{
Complex c;
c.real=c1.real-c2.real;
c.imag=c1.imag-c2.imag;
return c;
}
Complex operator-(double d1, Complex &c2)
{
Complex c(d1,0);
return c-c2;
}
Complex operator-(Complex &c1, double d2)
{
Complex c(d2,0);
return c1-c;
}

//复数相乘：(a+bi)(c+di)=(ac－bd)+(bc+ad)i.
Complex operator*(Complex &c1, Complex &c2)
{
Complex c;
c.real=c1.real*c2.real-c1.imag*c2.imag;
c.imag=c1.imag*c2.real+c1.real*c2.imag;
return c;
}
Complex operator*(double d1, Complex &c2)
{
Complex c(d1,0);
return c*c2;
}
Complex operator*(Complex &c1, double d2)
{
Complex c(d2,0);
return c1*c;
}

//复数相除：(a+bi)/(c+di)=(ac+bd)/(c^2+d^2) +(bc-ad)/(c^2+d^2)i
Complex operator/(Complex &c1, Complex &c2)
{
Complex c;
c.real=(c1.real*c2.real+c1.imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);
c.imag=(c1.imag*c2.real-c1.real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);
return c;
}
Complex operator/(double d1, Complex &c2)
{
Complex c(d1,0);
return c/c2;
}
Complex operator/(Complex &c1, double d2)
{
Complex c(d2,0);
return c1/c;
}

void Complex::display()
{
cout<<"("<<real<<","<<imag<<"i)"<<endl;
}

int main()
{
Complex c1(3,4),c2(5,-10),c3;
double d=11;
cout<<"c1=";
c1.display();
cout<<"c2=";
c2.display();
cout<<"d="<<d<<endl<<endl;
cout<<"下面是重载运算符的计算结果: "<<endl;
c3=c1+c2;
cout<<"c1+c2=";
c3.display();
cout<<"c1+d=";
(c1+d).display();
cout<<"d+c1=";
(d+c1).display();
c3=c1-c2;
cout<<"c1-c2=";
c3.display();
cout<<"c1-d=";
(c1-d).display();
cout<<"d-c1=";
(d-c1).display();
c3=c1*c2;
cout<<"c1*c2=";
c3.display();
cout<<"c1*d=";
(c1*d).display();
cout<<"d*c1=";
(d*c1).display();
c3=c1/c2;
cout<<"c1/c2=";
c3.display();
cout<<"c1/d=";
(c1/d).display();
cout<<"d/c1=";
(d/c1).display();
return 0;
}