In this issue, we have a detailed article on XML Serialization in .NET, and we will see how easy it is to mix and transform between C# (or any .NET language) objects and XML.

Winner from 2002!: One person was chosen randomly on December 23rd from the Techlet subscribers who wrote to us in 2002. Congratulations to Vijayabaskar Gangadar who is the winner of a $100 gift certificate from Amazon.com.

Please send suggestions, corrections and comments to techlet@durasoftcorp.com. Wish you all a very happy, safe and prosperous new year!

This month's quiz is exclusively for those who consider themselves savvy in C++. In the June article, we discussed about the issues with implementing the equals method in Java. The solution pretty much addresses how you can solve the problem in a language (like Java, .NET languages) that supports reflection. It got me thinking about how one can solve the problem of equals (operator==) in C++ efficiently. So, here is the question to you.

Can you implement the operator== for the code given below such that it produces the correct result?

#include 
using namespace std;

class Point
{
	public:
		// Showing only minimal code.
		virtual ~Point() {}
		Point(int px, int py) : x(px), y(py) {}
		virtual bool operator==(const Point& other) const
		{
			// Your code?
		}
	private:
		const int x;
		const int y;
};

class ColorPoint : public Point
{
	public:
		ColorPoint(int px, int py, int clr) : Point(px, py)
		{
			color = clr;
		}
	
		virtual bool operator==(const Point& other) const
		{
			// Your code?
		}
	private:
		int color;
};

void main()
{
	ColorPoint p1(1, 2, 5);
	Point p2(1, 2);
	ColorPoint p3(1, 2, 6);
	ColorPoint p4(1, 2, 5);

	cout << (p1 == p2) << endl;
	cout << (p2 == p1) << endl;
	cout << (p1 == p2) << endl;
	cout << (p2 == p3) << endl;
	cout << (p3 == p1) << endl;
	cout << (p1 == p4) << endl;
}				

Answer!

There are two answers to this question.

Answer 1:
Point::operator== method:

virtual bool operator==(const Point& other) const
{
	int* ptrToMyVptr = (int*) this;
	int* ptrToOthersVptr = (int*) &other;

	void* pMyVPtr = (void*) *ptrToMyVptr;
	void* pOthersVptr = (void*) *ptrToOthersVptr;

	if (pMyVPtr == pOthersVptr)
	{
		if (x ==  other.x && y == other.y)
			return true;
	}
	return false;
}

virtual bool operator==(const Point& other) const
{
	int* ptrToMyVptr = (int*) this;
	int* ptrToOthersVptr = (int*) &other;

	void* pMyVPtr = (void*) *ptrToMyVptr;
	void* pOthersVptr = (void*) *ptrToOthersVptr;

	if (pMyVPtr == pOthersVptr)
	{
		const ColorPoint* pOtherColorPoint = 
				dynamic_cast(&other);
		if (pOtherColorPoint == 0) return false;

		if (Point::operator==(other) && pOtherColorPoint->color == color)
			return true;
	}
	return false;
}

virtual bool operator==(const Point& other) const
{
	if (typeid(*this) == typeid(other))
	{
		if (x ==  other.x && y == other.y)
			return true;
	}
	return false;
}

virtual bool operator==(const Point& other) const
{
	if (typeid(*this) == typeid(other))
	{
		const ColorPoint* pOtherColorPoint = dynamic_cast(&other);
		if (pOtherColorPoint == 0) return false;
		if (Point::operator==(other) && pOtherColorPoint->color == color)
			return true;
	}
	return false;
}