#include <boost/typeof/typeof.hpp>
#include <iostream>

namespace A {

  template <typename T>
    class X {
      public:
        X() { }
        X(T t) : _t(t) { }
        const T &the_t() const { return _t; }
      private:
        T _t;
    };

  template <typename T1, typename T2>
    struct multiply_traits;

  template <typename T1, typename T2>
    struct multiply_traits<X<T1>, T2> {
      typedef X<T1> result_type;
    };

  template <typename T1, typename T2>
    typename multiply_traits<X<T1>, T2>::result_type operator*(const X<T1> &x, const T2 &t) {
      return X<T1>(x.the_t() * t);
    }

  template<class T>
    T make();

  template<class T1, class T2>
    struct multiply_traits {
      BOOST_TYPEOF_NESTED_TYPEDEF_TPL(nested, make<T1>() * make<T2>())
        typedef typename nested::type type;
    };

}

namespace B {

  template <typename T>
    class Y {
      public:
        Y(T t) : _t(t) { }
        const T &the_t() const { return _t; }
      private:
        T _t;
    };

  template <typename T1, typename T2>
  Y<typename A::multiply_traits<T1, T2>::result_type>
    operator*(const Y<T1> &y, const T2 &t) {
      return Y<T1>(y.the_t() * t);
    }
}

int main () {
  A::X<int> x(2);
  B::Y<A::X<int> > y(x);

  std::cout << (x * 3).the_t() << std::endl;
  std::cout << (y * 5).the_t().the_t() << std::endl;
}