重载运算符的函数可以是成员函数也可以是非成员函数，但它至少含有一个类类型的参数：

1.非成员函数

例1.

#include <iostream>
using namespace std;

class A{
  public:
	int x=96;
};

int operator+(A a,int b){
	return a.x+b;
}

int main(int argc,char * argv[]){
	A obj;
	cout<<obj+5<<endl;
	return 0;
}

例2.

#include <iostream>
using namespace std;

class Complex{
  public:
	Complex(){
	}
	Complex(int rx,int vx){
		r=rx,v=vx;
	}

	int r,v;
};

Complex operator+(Complex a,Complex b){
	Complex c;
	c.r=a.r+b.r;
	c.v=a.v+b.v;

	return c;
}

int main(int argc,char * argv[]){
	Complex a(1,3),b(6,12),c;
	c=a+b;
	cout<<c.r<<"+"<<c.v<<"i"<<endl;
	return 0;
}

2.成员函数

#include <iostream>
using namespace std;

class Complex{
  public:
	Complex(){
	}
	Complex(int rx,int vx){
		r=rx,v=vx;
	}

	Complex operator+(Complex a){//must take either zero or one argument
		Complex c;
		c.r=a.r+this->r;
		c.v=a.v+this->v;

		return c;
	}

	int r,v;
};

int main(int argc,char * argv[]){
	Complex a(1,3),b(6,12),c;
	c=a+b;
	cout<<c.r<<"+"<<c.v<<"i"<<endl;
	return 0;
}