多態與虛函數 4

#include <iostream>

using namespace std;

class Matrix;    // 前置聲明，
class Scalar;
class Vector;

class Math
{
public:
	virtual Math& operator*(Math& rv) = 0;  // 虛的運算符重載，
	virtual Math& multiply(Matrix*) = 0;
	virtual Math& multiply(Scalar*) = 0;
	virtual Math& multiply(Vector*) = 0;

	virtual ~Math() {}
};

class Matrix : public Math
{
public:
	Math& operator*(Math& rv)
	{
		return rv.multiply(this);   //  二次指派，
	}
	Math& multiply(Matrix*)
	{
		cout << "Matrix * Matrix" << endl;
		return *this;
	}
	Math& multiply(Scalar*)
	{
		cout << "Scalar * Matrix" << endl;
		return *this;
	}
	Math& multiply(Vector*)
	{
		cout << "Vector * Matrix" << endl;
		return *this;
	}
};

class Scalar : public Math
{
	Math& operator*(Math& rv)
	{
		return rv.multiply(this);
	}

	Math& multiply(Matrix*)
	{
		cout << "Matrix * Scalar" << endl;
		return *this;
	}
	Math& multiply(Scalar*)
	{
		cout << "Scalar * Scalar" << endl;
		return *this;
	}
	Math& multiply(Vector*)
	{
		cout << "Vector * Scalar" << endl;
		return *this;
	}
};

class Vector : public Math
{
	Math& operator*(Math& rv)
	{
		return rv.multiply(this);
	}

	Math& multiply(Matrix*)
	{
		cout << "Matrix * Vector" << endl;
		return *this;
	}
	Math& multiply(Scalar*)
	{
		cout << "Scalar * Vector" << endl;
		return *this;
	}
	Math& multiply(Vector*)
	{
		cout << "Vector * Vector" << endl;
		return *this;
	}
};

class Pet
{
public:
	virtual ~Pet(){}
};

class Dog : public Pet{};
class Cat : public Pet{};

class Shape
{
public :
	virtual ~Shape(){}
};

class Circle : public Shape{};
class Square : public Shape{};
class other {};

int main()
{
	Circle c;
	Shape* sh = &c;   // 向上類型轉換，
	 sh = static_cast<Shape*> (&c);  // 這個是靜態的向上類型轉換，

	 Circle* cp = 0;
	 Square* sp = 0;

	 //cout << typeid(*sh).name() << endl;
	 

	 if (strcmp(typeid(*sh).name(),"class Circle") == 0)    // strcmp 是顯示字符串，
		 cp = static_cast<Circle*>(sh);  // 向下類型轉換，
	 if (strcmp(typeid(*sh).name(), "class Square") == 0)
		 sp = static_cast<Square*>(sh);

	 if (cp != 0)
		 cout << "It's a Circle ! " << endl;
	 if (sp != 0)
		 cout << "It's a Square ! " << endl;



	Pet* b = new Cat;
	Cat* d1 = dynamic_cast<Cat*> (b);  // 動態的向下類型轉換，dynamic_cast執行的時候速度會慢一些，
	Dog* d2 = dynamic_cast<Dog*> (b);  // 這是一個錯誤的向下類型轉換，

	cout << " d1 = " << (long)d1 << endl;
	cout << " d2 = " << (long)d2 << endl;  // d2 = 0, 0 指針

	Matrix m;
	Vector v;
	Scalar s;
	Math* math[] = { &m, &v, &s };

	for (int i = 0; i < 3; i++)
	for (int j = 0; j < 3; j++)
	{
		Math& m1 = *math[i];
		Math& m2 = *math[j];
		m1 * m2;
	}


	return 0;
}