// A5.cpp - what contructors are needed?  Describe all operations.

#include <iostream>
using namespace std;

class X {
  public:
    X(int val) { x = val; }
    X operator-() { X temp(-x); return temp; }
    int value() { return x; }
    void store(int val) { x = val; }
  private:
    int x;
};

class Y : public X { 
  public:
    Y(int y) : X(y) { store(y); }
};

X aFunction(X &x) { return -x.value(); }

void main() {

/////////////////////////////////////////////////////////////////////
// In the statement below:
// - promotion constructor Y::(int) is called which in turn calls
//   promotion constructor X::(int)

  Y y1(5);
  cout << "\n  y1's value is " << y1.value();
  
/////////////////////////////////////////////////////////////////////
// In the statement below:
// - y1 is passed by reference, so no constructor is called
// - x, inside aFunction(...), is a reference to y1, so, the 
//   inherited X::value() is called.
// - value returns an int, so aFunction must return it by calling
//   the X::X(int)
// - x2 is copy constructed, using the returned X value and compiler
//   generated copy constructor.

  X x2 = aFunction(y1);
  cout << "\n  x2's value is " << x2.value();

  cout << "\n\n";
}