A preliminary study of C + + operator overloading Learning notes <2> Overload as Friend function

A preliminary study on C + + operator overloading Learning notes

In the previous blog, we wrote about overloading operators with normal functions or member functions of classes .

The following two conditions occur. Then we need to overload the operator with the friend function of the class

<1> member functions do not meet the requirements

<2> Normal functions cannot access private members of a class

To illustrate:

Class complex{    double Real, imag;    Public:    Complex (Double R, double i): Real (R), Imag (i) {};     Complex operator+ (Double R);   };    Complex complex::operator+ (Double r) {    return Complex (real + R, imag);}

Defines a complex number class. Overloaded ' + ' operators, after overloading

Complex C = c + 5;  There is a definition, equivalent to C = C.operator + (5);

However, if 5+c is present, the compilation problem occurs. You also need to overload the normal function at this point.

Complex operator+ (Double R, const Complex & c) {    return Complex (C.real + R, C.imag);}

Can explain 5+c, but the normal function cannot access the private members of the class.

In this case, you need to overload the friend function for the class

Class Complex {    double real, imag;    Public:    Complex (Double R, double i): Real (R), Imag (i) {};     Complex operator+ (Double R);    Friend Complex operator + (double R, const Complex & c);};

A preliminary study of C + + operator overloading Learning notes &lt;2&gt; Overload as Friend function