///////////////////////////////////////////////////////////////
//  relation.cpp  -  demonstrate class relationships         //
///////////////////////////////////////////////////////////////

#include <iostream>
using namespace std;

class A {     // objects of A will be aggregated by B
  public:
    A()                      { cout << "  void constructing A object\n";  }
    A(const A &a)            { cout << "  copy constructing A object\n";  }
    ~A()                     { cout << "  destructing A object\n";        }
    int& getInt()   { cout << "  accessing A's private int\n"; return ai; }
  private:
    int ai;     // B and D have no access to ai accept through getInt()
};

class B {     // B class is base for inheritance used by D
  public:
    B() : bi(0)              { cout << "  void constructing B object\n";  }
    B(const B &b) : _a(b._a), bi(b.bi)
                             { cout << "  copy constructing B object\n";  }
    ~B()                     { cout << "  destructing B object\n";        }
    int& iPart()  { cout << "  accessing B's protected int\n"; return bi; }
  protected:
    A _a; int bi;
};

class D : public B {
  public:
    D()                       { cout << "  void constructing D object\n"; }
    D(const D &d) : B(d)      { cout << "  copy constructing D object\n"; }
    ~D()                      { cout << "  destructing D object\n";       }
    int iBPart() const { cout << "  reading B's protected int\n"; return bi; } 
};

void msg(char *s) { cout << s << endl; };

void main() {

  msg("\n<<<<<<<<---- entering scope #1 ---->>>>>>>>");  {  
     msg("1st statement:");   A a1;
     msg("2nd statement:");   A a2 = a1;
     msg("3rd statement:");   a2.getInt();
  msg("<<<<<<<<---- leaving scope #1  ---->>>>>>>>");    }
  
  msg("\n<<<<<<<<---- entering scope #2 ---->>>>>>>>");  {
     msg("1st statement:");   B b1;
     msg("2nd statement:");   B b2 = b1;
     msg("3rd statement:");   b2.iPart() = 5;
  msg("<<<<<<<<---- leaving scope #2  ---->>>>>>>>");    }

  msg("\n<<<<<<<<---- entering scope #3 ---->>>>>>>>");  {
     msg("1st statement:");   D d1;
     msg("2nd statement:");   D d2 = d1;
     msg("3rd statement:");   d2.iPart() = 4;
     msg("4th statement:");   cout << "  D's iPart inherited from B = " 
                                   << d2.iBPart() << endl;
  msg("<<<<<<<<---- leaving scope #3  ---->>>>>>>>");    }

}