運算子的過載：

1，只能過載已存在的運算子

2，自定義型別和內建滿足的相同的邏輯

1.普通運算子可以過載

2.型別過載

const ：

1、防止實參被修改；

2、接收隱式生成臨時物件；

類內是this_call的呼叫約定，成員方法隱藏this指標，指向一般為左運算元，所以只用傳右運算元即可

程式碼如下：

class CComplex
{

public:

CComplex(int real, int img) :mreal(real), mimg(img){}  //構造

類內實現+的過載 右運算元型別為int

const CComplex operator+(int rhs)    
	{
		std::cout << "CComplex::operator+(int)" << std::endl;
		return CComplex(mreal + rhs, mimg);
	}
 

CComplex cc2 = cc1 + 10; //cc1.operator+(10);

//類內實現<<的過載

//std::ostream& operator<<(std::ostream& out)
	//{
	//	out << mreal << " ";
	//	out << mimg << " ";
	//	return out;
	//}

//cc1 << std::cout;左運算元是類內的物件

private:

int mreal;   //實部
int mimg;    //虛部

//類外不能訪問類內的私有成員變數，設定友元函式

friend const CComplex operator+(int, const CComplex&);
	friend const CComplex operator+(const CComplex&, const CComplex&);
	friend std::ostream& operator <<(std::ostream&, const CComplex&);
};

類外是cd_call的呼叫約定,無this指標，需傳兩個物件

//類外實現+的過載 左運算元型別為int,右運算元型別為CComplex

const CComplex operator+(int lhs, const CComplex& rhs)
{
	std::cout << "global::operator+(int,CComplex)" << std::endl;
	return CComplex(lhs + rhs.mreal, rhs.mimg);
}
 

CComplex cc3 = 10 + cc2; //operator+(10,cc2);

//類外實現+的過載 左操右運算元型別都為CComplex

 const CComplex operator+(const CComplex& lhs, const CComplex& rhs)
    {
    	std::cout << "CComplex::operator+(CComplex, CComplex)" << std::endl;
    	return CComplex(lhs.mreal + rhs.mreal, lhs.mimg + rhs.mimg);
    }
CComplex cc4 = cc2 + cc3;

//類外實現<<的過載 左運算元為std::ostream的型別，右運算元為CComplex型別

std::ostream& operator <<(std::ostream& out, const CComplex& rhs)
{
	out << rhs.mreal << " ";
	out << rhs.mimg << " ";
	return out;
}

std::cout << cc1 << std::endl;