14.1-13 Template parameters. Using beta 12:

template<class T, class U> class A { };

template<class T = unsigned long, class U = int>
class B : public A<T, U> { };
//Error: type-argument expected for parameter 'T' of template 'A'

void main() {

B<> b;

}

Part of boost dynamic_bitset<> class

Richard