Re: pure virtual function in template class

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Sun, 13 Jul 2008 04:53:55 +0200

Message-ID:

<1p-dnSw11dnV8-TVnZ2dnUVZ_uqdnZ2d@posted.comnet>

* Mike -- Email Ignored:

On Fri, 11 Jul 2008 02:08:45 -0700, James Kanze wrote:

On Jul 10, 2:49 pm, Mike -- Email Ignored <m_d_berger_1...@yahoo.com>
wrote:

Is a pure virtual function in allowed in a template base class? In any
case, I have one working. Am I skating on thin ice?

No. Why should there be any problem? The instantiation of a class
template is just like any other class. The same rules apply.

How about, then, a template class virtual member function that
is not pure? It is my understanding that such a virtual function
may not be inline, but, at least on the gnu c++ compiler, non-pure
functions of a template class must be inline (unless there have
been recent developments I do not know about).

I don't understand what you're trying to say.

The following compiles fine with MinGW g++ 3.4.5:

     template< class T >
     struct A
     {
         virtual void foo() {}
     };

     template< class T >
     struct B
     {
         virtual void foo();
     };

     template< class T >
     void B<T>::foo() {}

     int main ()
     {
         A<int> a;
         B<int> b;
     }

It seems to me that this contains a counter-example to each possible meaning of
what you write, but, what is it really that you're trying to express?

Cheers,

- Alf

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