Chapter 10 Operator Overloading

1. 重载为成员函数

双目：

class ClassName

{

public:

 DataType operator@(Parameter List); …

};

DataType ClassName::operator@ (Parameter List) { … }

aa@bb    //or aa . operator @ (bb)

单目：

class ClassName

{

public:

DataType operator@(  ); …

};

DataType ClassName::operator@ (  ) { … }

@aa    //or aa.operator @ ( )

默认为前置

Complex operator ++ ( );

后置的话形参列表里有一个int，本身无作用只是为了区分

Complex Complex∷operator ++ ( int )

c2=c1++; //or c2=c1.operator++(0);

1. 重载为友元函数

class ClassName

{

public:

friendDataType operator@(Parameter List); …

 };

DataType operator@ (Parameter List) { … }

aa@bb    //or operator @ (aa , bb)

默认为前置Complex operator ++ (Complex &c )

后置的话同理Complex operator ++ (Complex & c, int )

1. 重载为成员函数：

双目运算符参数列表有一个参数，单目运算无参数

重载为友员函数：

双目运算符参数列表有两个参数，单目运算有一个参数

1. Rules for Operator Overloading 

can not define newoperators 

can not change the numberof operands 

can not change the precedence 

can not change the associativity（结合性） 

can not have default parameters “=”, “( )”, “[ ]”

can only be overloaded as member functions “.”, “.*”, “::”, “sizeof”, “?:” can not be overloaded

1. 重载赋值运算符

ClassName&ClassName::operator =( const ClassName & source )

{

real= source.real; imag= source.imag; return *this; //注意返回值

}

1. 重载输入输出运算符

重载为友元函数 friend ostream & operator <<(ostream & , ClassName & );

ostream & operator <<(ostream & , ClassName & )

{  

output<<“( ”<<c.real<<“ , ” <<c.imag<<“i )” <<endl;

return output;//注意返回值

 }

friend istream & operator >>(istream & , ClassName & );

istream & operator >>(istream & input, Complex &c)

{

cout<<“Input the real part and” <<“imaginary part of a” <<“complex number:”; input>>c.real>>c.imag;

return input;

 }

1. 强制类型转换？

class ClassName{ public: operator DataType( ); … }