C++ inheritance function overriding

Question

I have a question (part of my homework) which im unsure of the code's behavior.

I got a class Father, which owns a function "A", function "A" prints "Hello Father".
I got a second class -> class son:public Father, which does not owns function "A".
I got a third class -> class grandson:public son , which owns function "A" which prints "Hello grandson".

Function "A" is not virtual. Please ignore compiling errors, I didnt want to put here a 80 lines of code.

I have another function :

void justPrint(const son& a) {
   a.A;
}

Now, what will be printed in the following call :

grandson jeff;
justPrint(jeff);

I'm a bit confused, son dont have the print function (A), so he suppose to call to Father::A (son is a father..)
but, we send jeff (grandson) to the function which recieves son.. and grandson is a son..

I think that it will print

"Hello Father"

But i'm so confused... Will appericiate any help and explenation..

Second thing, What will happen if i will make the following call :

justPrint(1);

Actually justPrint function as described will not compile - or at least it won't call function A. And justPrint(1), assuming there is only the function above also will not compile (as 1 is not a valid class son object). — Mats Petersson
– Mats Petersson, Commented Jul 1, 2013 at 11:47
And to be able to answer the question (ignoring errors mentioned above), we need to know if function A in the class father is virtual or not. — Mats Petersson
– Mats Petersson, Commented Jul 1, 2013 at 11:49

Krozark · Accepted Answer · 2013-07-01 12:00:04Z

1

I try to make a short code to solve your problem, but I don't have it (using "g++ test.cpp -fpermissive" to compile)

#include <iostream>

using namespace std;

class Father
{
    public:
    void A(){
        cout<<"Hello Father"<<endl;
    }
};

class Son : public Father
{
};

class GrandSon : public Son
{
    public:
    void A()
    {
        cout<<"Hello GrandSon"<<endl;
    }
};

void justPrint(const Son& a)
{
    a.A();
}

int main(int argc, char* argv[])
{
    GrandSon jeff;
    justPrint(jeff);
    return 0;
}

Maybe you have put A in private?

Output: Hello Father

answered Jul 1, 2013 at 12:00

Krozark

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2 Comments

Nadav Peled Over a year ago

Hi, This is what i think it should print (as you can see in my answer), But I was not sure.

Krozark Over a year ago

It's because you have use "class Son : public Father" to build Son. So Son have have all public methode that Father have (include A()). Morover, Son don't have a A(), so it use the heritance tree, and take the first one "A" (here in Father::A) with the same signature.

vinod · Accepted Answer · 2013-07-01 11:52:01Z

0

void justPrint(const son& a) {
   a.A;
}

justPrint(1); if Class son contains single argument constructor with int as i/p.It will call that .

answered Jul 1, 2013 at 11:52

vinod

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2 Comments

Nadav Peled Over a year ago

class son does contains a single argument constructor. Can you please explain me why it will be called ?

doctorlove Over a year ago

It will be called if it takes an int, unless you mark it explicit

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