Untitled

C  : partial specialization of template template classes
using namespace std;

template <typename X>
class Goo {};


template <typename X>
class Hoo {};


template <class A, template <typename> class B = Goo >
struct Foo {
  B<A> data;
  void foo1();
  void foo2();

};


template <typename A>
void Foo<A>::foo1() { cout << "foo1 for Goo" << endl;}


int main() {
  Foo<int> a;
  a.foo1();

}

test.cc:18: error: invalid use of incomplete type 'struct Foo<A, Goo>'
test.cc:11: error: declaration of 'struct Foo<A, Goo>'

template <>
void Foo<int, Goo>::foo1() { }  // OK

template <typename A>
struct Foo<A, Goo>
{
  // ...
};

template <typename A, template <typename> class B>
void Foo<A,B>::foo1() { cout << "foo1" << endl;}