贺老师的教学链接  本课讲解

//类型转换函数应用
#include <iostream>
using namespace std;
class Complex
{
public:
    Complex( )
    {
        real=0;
        imag=0;
    }
    Complex(double r,double i)
    {
        real=r;
        imag=i;
    }
    operator double( );
    friend Complex operator + (Complex c1,Complex c2);
private:
    double real;
    double imag;
};

Complex operator + (Complex c1,Complex c2)  //定义运算符“+”重载函数
{
    return Complex(c1.real+c2.real, c1.imag+c2.imag);
}

Complex::operator double( )
{
    return real;
}

int main( )
{
    Complex c1(3.5,4),c2(5,-10);
    double d1,d2;
    d1=2.5+c1;
    cout<<d1<<endl;
    d2=c1+c2;
    cout<<d2<<endl;
    return 0;
}