Re: Templates and derivation

"Manfred von Willich" <>
13 Jun 2006 18:29:01 -0400
Lars Jordan wrote:

My question is. Are there other solutions which solve the problem from described
  above? Is there a solution which avoids the usage of such a ImplType-like member?

I have stripped out extras, leaving the minimum. What I have given
compiles successfully, even when using your Holder class. Essentially,
two lines change: the addition of a template operator to template class
MF, and the need for the explicit invocation of this operator to get
the compiler to recognise the conversion.

template<typename T> class MF : public T
   template<typename B> operator MF<B>& () { return *this; }

class Base
   virtual ~Base() { }

class Derived : public Base
   virtual ~Derived() { }

int main( int, char*[] )
   MF<Derived>* pMFD = new MF<Derived>;
   MF<Base>* pMFB = &(MF<Base>&)*pMFD;
   return 0;

I do not know if it can be done without explicitly invoking a
conversion operator. I hope this is something like what you are
looking for.


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