list1407.cpp

teach yourself C++ in 21 days 第五版

//Listing 14.7. Shape classes.

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

class Shape
{
  public:
    Shape(){}
    virtual ~Shape(){}
    virtual long GetArea() { return -1; } // error
    virtual long GetPerim() { return -1; }
    virtual void Draw() {}
  private:
};

class Circle : public Shape
{
  public:
    Circle(int radius):itsRadius(radius){}
    ~Circle(){}
    long GetArea() { return 3 * itsRadius * itsRadius; }
    long GetPerim() { return 6 * itsRadius; }
    void Draw();
  private:
    int itsRadius;
    int itsCircumference;
};

void Circle::Draw()
{
   cout << "Circle drawing routine here!\n";
}


class Rectangle : public Shape
{
  public:
    Rectangle(int len, int width):
    itsLength(len), itsWidth(width){}
    virtual ~Rectangle(){}
    virtual long GetArea() { return itsLength * itsWidth; }
    virtual long GetPerim() {return 2*itsLength + 2*itsWidth; }
    virtual int GetLength() { return itsLength; }
    virtual int GetWidth() { return itsWidth; }
    virtual void Draw();
  private:
    int itsWidth;
    int itsLength;
};

void Rectangle::Draw()
{
   for (int i = 0; i<itsLength; i++)
   {
      for (int j = 0; j<itsWidth; j++)
         cout << "x ";

   cout << "\n";
   }
}

class Square : public Rectangle
{
  public:
    Square(int len);
    Square(int len, int width);
    ~Square(){}
    long GetPerim() {return 4 * GetLength();}
};

Square::Square(int len):
Rectangle(len,len)
{}

Square::Square(int len, int width):
Rectangle(len,width)
{
   if (GetLength() != GetWidth())
   cout << "Error, not a square... a Rectangle??\n";
}

int main()
{
   int choice;
   bool fQuit = false;
   Shape * sp;

   while ( !fQuit )
   {
      cout << "(1)Circle (2)Rectangle (3)Square (0)Quit: ";
      cin >> choice;

      switch (choice)
      {
        case 0:   fQuit = true;
           break;
        case 1: sp = new Circle(5);
           break;
        case 2: sp = new Rectangle(4,6);
           break;
        case 3: sp = new Square(5);
           break;
        default: 
           cout <<"Please enter a number between 0 and 3"<<endl;
           continue;
           break;
      }
      if( !fQuit )
         sp->Draw();
      delete sp;
      sp = 0;
      cout << endl;
   }
   return 0;
}