Question

Any help will be appreciated please...

Compile and run the file. If you find any compilation errors,explain their reason as comments in the code. Then fix the errors such that the program compiles and runs. Explain the motivation of your modifications in the code and their effects on the execution.

--- inheritance2 file---

#include<iostream>
using namespace std;

class A
{
int x;
public:
A(int i) { x = i; }
void print() { cout << x; }
};

class B: virtual public A
{
public:
B():A(10) { }
};

class C: virtual public A
{
public:
C():A(10) { }
};

class D: public B, public C {
};

int main()
{
D d;
d.print();
return 0;
}

Answer 1

The errors occurred because class D was not able to call the constructor of class A as class A only has a parameterized constructor and no default constructor, class D tries to call class A's default constructor but since there is no default constructor specified for class A we get errors. These errors can be prevented in two ways:

1. You create a default constructor for class A
2. You create a constructor for class D which calls the constructor of A with a parameter.

1. Removing errors using the first method:

#include<iostream>

using namespace std;

class A

{

    int x;

public:

    A() { x = 0; } // This is class A's default constructor

    A(int i) { x = i; }

    void print() { cout << x; }

};

class B: virtual public A

{

public:

    B():A(10) { }

};

class C: virtual public A

{

public:

    C():A(10) { }

};

class D: public B, public C {

};

int main()

{

    D d;

    d.print();

    return 0;

}

2. Removing errors using the second method:

#include<iostream>

using namespace std;

class A

{

    int x;

public:

    A(int i) { x = i; }

    void print() { cout << x; }

};

class B: virtual public A

{

public:

    B():A(10) { }

};

class C: virtual public A

{

public:

    C():A(10) { }

};

class D: public B, public C {

public:

    D() : B(), C(), A(10) {} // This is class D's default constructor which calls A's constructor with 10

};

int main()

{

    D d;

    d.print();

    return 0;

}