#include <iostream>

class X {
   public:
      X() {
	 std::cout << "an object of type X gets default-constructed"
	    << std::endl;
      }
      ~X() {
	 std::cout << "an object of type X gets destructed" << std::endl;
      }
};

class Y {
   public:
      Y() {
	 std::cout << "an object of type Y gets default-constructed"
	    << std::endl;
      }
      ~Y() {
	 std::cout << "an object of type Y gets destructed" << std::endl;
      }
};

class Z {
   public:
      Z() {
	 std::cout << "an object of type Z gets default-constructed"
	    << std::endl;
      }
      ~Z() {
	 std::cout << "an object of type Z gets destructed" << std::endl;
      }
   private:
      X x;
      Y y;
};

int main() {
   Z z; /* invokes compiler-provided default constructor */
}