Cant use brother methods with virtual inheritance cpp - c++

Question

Because of virtual inheritance, when the write() function from the
transmitter class is called, the method read() from the receiver class
gets called (as you may have noticed, the transmitter class doesn't
have a read() function). In the above hierarchy we can instantiate
only the radio class because transmitter and receiver are abstract due
to virtual inheritance.
http://www.cprogramming.com/tutorial/virtual_inheritance.html
So I tried it and it didnt worked for me.
#pragma once
#include <iostream>
using namespace std;
father class:
class father
{
public:
father(){
};
~father(){};
virtual void printt() = 0;
void sett()
{
printt();
}
void father()
{
cout << "Im your father...";
}
private:
};
Person:
#pragma once
#include <iostream>
using namespace std;
#include "father.h"
class MyClasst: public virtual father
{
public:
MyClasst(){
g = 8;
};
~MyClasst(){};
void print()
{
cout << "a";
}
void c()
{
cout << "bbb";
}
private:
...
};
Student class:
#pragma once
#include <iostream>
#include "father.h"
using namespace std;
class MyClassa: public virtual father
{
public:
MyClassa(){
};
~MyClassa(){};
void printt()
{
cout << "b";
}
void b()
{
c();
printt();
}
private:
...
};
By the rules above, I should be able to call 'c()' from person class in 'b()' ('b()' is function of Student which is virtual brother of 'Person class').
But I get an error:
Error 1 error C3861: 'c': identifier not
found c:\users\micha\onedrive\מסמכים\visual studio
2013\projects\project7\project7\student.h 21 1 Project7

Answer 1

This is because the "c()" function is not declared in the base class "father" and your class "MyClassa" derives only from "father".
Consequently, an object of class "MyClassa" will not contain any function "c()".
An object of a class deriving from "MyClasst" (as well as an object deriving from both "MyClassa" and "MyClasst" will have it).
If you want to have your code compiling, you must add a declaration of "c()" in the parent class. Add the line "virtual void c() = 0;" in the class "father" - then will compile. Live example here: http://rextester.com/OBBC17077

Answer 2

There is no method c() in MyClassa directly nor inherited from father. There is a method c() in MyClasst, but the two classes have no relation apart from inheriting both from father, but that doesnt allow them to call methods from each other.
Imho the analogy with the so called "parent class" and "child classes" does not make much sense and only leads to confusion. It doesnt make sense to say "a child is-a parent", but thats what (public) inheritance actually is. I would advice you to forget about the term "brother class". It doesnt help you to understand anything. And btw the error you get has little to do with the virtual inheritance. You would get the same error with public inheritance.