[C++] Operator Overload

　　　　　　　　Operator Overload

　NOTE1:

　　 operator = must be overload as a member function

NOTE2:

  An operator function must either be a member of a class or have at least one parameter of class type.

 

//操作符重载，有一个最基本条件，就是一定有一个一元是一个自定义的C++类
//如果两个都是基本数据类型操作符重载是非法的

NOTE3:

　An overload operator function has the same number of parameters as the operator has operands .

　A unary(一元) opeartor has one parameter;

　A binary(二元)  opeartor has two parameter ，the left-hand operand is passed to thr first parameter

　and the right-hand operand to the second .

　

NOTE4：

   When an overloaded operator is a member function , this is bound to left-hand operand.

   Member operator functions have one less(explict) parameter than the number of opeands.

　成员操作函数少一个隐式参数：this

NOTE5:

//如果返回的是char，代表的是一个右值，右值是不能直接赋值的，
//如果返回的是char的引用，那么[]就可以当左值使用了

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