// Example C++ Classes
// George F. Riley, Georgia Tech, Spring 2009

#include <iostream> // Needed for the "cout" commands

using namespace std;

// Define a C Structure called TwoInt_t
typedef struct 
{
  int a;
  int b;
} TwoInt_t;

void PrintTwo(TwoInt_t* ti)
{
  cout << "a " << ti->a << " b " << ti->b << endl;
}

// Define a second structure with TwoInt_t as an element
typedef struct
{
  TwoInt_t ti;
  int      c;
  int      d;
} FourInt_t;

void PrintFour(FourInt_t* fi)
{
  cout << "a " << fi->ti.a << " b " << fi->ti.b
       << " c " << fi->c << " d " << fi->d << endl;
}

// Define a C++ Class that does the same thing as TwoInt_t
class TwoInt 
{
public:
  int a;
  int b;
};

void PrintTwo(TwoInt* ti)
{
  cout << "a " << ti->a << " b " << ti->b << endl;
}

// Define a C++ Class that does the same thing as TwoInt_t
// plus a "Constructor"
class TwoIntC
{
public:
  TwoIntC();
public:
  int a;
  int b;
};

//NewPage
// Code for TwoIntC constructor
TwoIntC::TwoIntC()
{
  a = 1000;
  b = 1001;
}

void PrintTwo(TwoIntC* ti)
{
  cout << "a " << ti->a << " b " << ti->b << endl;
}

// Demonstrate a C++ "reference" argument.
// More about this later in the semester
void PrintTwo(const TwoIntC& ti)
{
  cout << "a " << ti.a << " b " << ti.b << endl;
}

// Make a subclass of TwoIntC called FourInt
class FourInt : public TwoIntC {
public:
  FourInt();  // Constructor
public:
  int c;
  int d;
};

    
// Code for FourInt constructor
FourInt::FourInt() 
    : TwoIntC()
{
  c = 3001;
  d = 3002;
}

// Define a subroutine to print FourInt variables c and d
void PrintFour(FourInt* fi)
{
  cout << "c " << fi->c << " d " << fi->d << endl;
}

//NewPage
int main()
{
  TwoInt_t a; // Uninitialized
  // Print the uninitialized one
  PrintTwo(&a);
  
  // Declare another one, and initialize it
  TwoInt_t b; // Initialized below
  b.a = 1;
  b.b = 2;
  PrintTwo(&b);

  // Declare a FourInt variable
  FourInt_t f;
  f.ti.a = 10;
  f.ti.b = 11;
  f.c    = 12;
  f.d    = 13;
  PrintFour(&f);
  
  // Now try a trick.  Pass the FourInt variable to PrintTwo
  PrintTwo((TwoInt_t*)&f);
  //PrintTwo(&f);
  
  //  Declare a variable of class TwoInt
  TwoInt cTi;
  // Since we have no constructor in class TwoInt, a and b are random
  PrintTwo(&cTi);
  // Initialize a and b to good values.
  cTi.a = 20;
  cTi.b = 21;
  PrintTwo((TwoInt_t*)&cTi);

  // Declare a variable of class TwoIntC
  TwoIntC cTiC;
  PrintTwo(&cTiC);
  // Call the PrintTwo with the reference argument
  PrintTwo(cTiC);

  // Declare a variable of class FourInt
  FourInt fi;
  PrintTwo(&fi); // Note we are calling the "TwoInt" printer
  PrintFour(&fi);
}