12 Templates [temp]

// primary class template
template<class T, int I> struct A {
  void f();
};

// member of primary class template
template<class T, int I> void A<T,I>::f() { }

// class template partial specialization
template<class T> struct A<T,2> {
  void f();
  void g();
  void h();
};

// member of class template partial specialization
template<class T> void A<T,2>::g() { }

// explicit specialization
template<> void A<char,2>::h() { }

int main() {
  A<char,0> a0;
  A<char,2> a2;
  a0.f();           // OK, uses definition of primary template's member
  a2.g();           // OK, uses definition of partial specialization's member
  a2.h();           // OK, uses definition of explicit specialization's member
  a2.f();           // ill-formed, no definition of f for A<T,2>; the primary template is not used here
}

template<class T> struct A {
  template<class T2> struct B {};                     // #1
  template<class T2> struct B<T2*> {};                // #2
};

template<> template<class T2> struct A<short>::B {};  // #3

A<char>::B<int*>  abcip;                              // uses #2
A<short>::B<int*> absip;                              // uses #3
A<char>::B<int>  abci;                                // uses #1