Re: Polymorphism via Inheritance not working as planned

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Tue, 23 May 2006 13:23:29 -0400

Message-ID:

<e4vgeh$rhk$1@news.datemas.de>

joe wrote:

I expected this to work:

On what grounds?

class Base
{
virtual void go(int *) {cout<<"BASE CLASS"<<endl;}
};

class Derived : public Base
{
template<typename T>
void go(T*) {cout<<"Derived Class"<<endl;}

Here is a possible problem: a member template cannot be virtual.
So, even if 'T' *is* 'int', you're not going to achieve making the
instantiation of that template the final overrider to 'Base::go'.

};

int main(){
Base *b = new Derived;
b->go(new int[30]);
}

I get "BASE CLASS". I expected the virtual function to work and find
the derived class function.

Why? The derived class' member is not the overrider for the base's one.

What's the nitty gritty here of what's going on?

When you call 'go', how should the compiler know you're trying to call
the template? If you were allowed to make 'Derived::go' virtual, how
many virtual functions would 'Derived' have?

V
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