Thread: implementing a polymorphic function in C++

A - C is incorrect. D & E is correct.
Basically, what A is asking is this:

Code:

Derived* p = new Derived;

Is this a requirement for polymorphism?

D asks the same, but using a Base class pointer.

Originally Posted by coletek

* A is incorrect - but I really don't understand the answer given.

The sentence might be ambiguous, but my interpretation is that it is asking if you need a derived class pointer to point to an object of the corresponding derived class in order to implement a relevant polymorphic function. The answer would be no because this is not relevant to the question, since this involves using the polymorphic function via a pointer instead of implementing it. Also, such a function call would be statically bound, not dynamically bound, and by "polymorphic" we presumably mean runtime polymorphism achieved by dynamic binding.

Originally Posted by coletek

* B is incorrect, because virtual keyword is not need in the derived class.
* C is incorrect. because to be polymorphic it doesn't have to be pur virtual.

I agree.

Originally Posted by coletek

* D is incorrect - but I really don't understand the answer given.

Refer to my explanation for A. This time, the statement talks about using a base class pointer to point to an object of a relevant derived class. Now, in this case dynamic binding would be applicable, and there might be actual use of runtime polymorphism. But like in A, this is about using polymorphism, not about implementing a function, so the answer should be no.

Originally Posted by coletek

* E is correct

I agree.

Also for D, polymorphism can also be done with references.

We'll all have law degrees soon.