Question

I have ClassA<ARG_TYPE> and ClassB<ARG_TYPE>. Now I want want to use ClassC, that has common ARG_TYPE and mentioned classes as template arguments.

ClassC<ARG_TYPE, ClassA<ARG_TYPE>, ClassB<ARG_TYPE>> is easy.

But is it possible do declare ClassC<ARG_TYPE, ClassA, ClassB> so that both A and B classes would know to use ARG_TYPE as their template argument?

Answer 1

Yes, it can be done, through the use of “template template arguments”.

Declare ClassC as follows :

template<typename Arg, 
    template<typename T_Arg> class T_ClassA, 
    template<typename T_Arg> class T_ClassB>
class ClassC
{
   typedef T_ClassA<Arg> MyClassA;
   typedef T_ClassB<Arg> MyClassB;

   // Use MyClassA and MyClassB
}; 

Use

ClassC<Arg, ClassA, ClassB> 

and it should work fine.