poly.cpp

适合初学者学习以及程序员回顾

// Poly.cpp

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

//---- 宣告类别 Shape --------
class Shape
{
private:
  int i;
public:
  Shape(): i(7){}
  ~Shape(){}
  virtual void Draw()  {cout<<"画个图\n";}
  virtual void Erase() {cout<<"将图清除\n";}
};

//---- 宣告类别 Circle--------
class Circle : public Shape
{
private:
  int r;
public:
  Circle(): r(5)      {}
  Circle(int N): r(N) {}
  ~Circle()           {}
  void Draw()  {cout<<"画一个圆形\n";}
  void Erase() {cout<<"把圆形清除\n";}
};
//---- 宣告类别 Square --------
class Square : public Shape
{
private:
  int a;
public:
  Square(): a(2)      {}
  Square(int N): a(N) {}
  ~Square()           {}
  void Draw()  {cout<<"画一个正方形\n";}
  void Erase() {cout<<"把正方形清除\n";}
};

//---- 宣告类别 Triangle --------
class Triangle : public Shape
{
private:
  int a, b, c;
public:
  Triangle(): a(1), b(1), c(1)      {}
  Triangle(int L, int M, int N): a(L), b(M), c(N) {}
  ~Triangle()           {}
  void Draw()  {cout<<"画一个三角形\n";}
  void Erase() {cout<<"把三角形清除\n";}
};

//---- 宣告类别 Cylinder--------
class Cylinder : public Circle
{
private:
  int r, h;
public:
  Cylinder(): r(5), h(1)    {}
  Cylinder(int M, int N): r(M), h(N) {}
  ~Cylinder()         {}
  void Draw()  {cout<<"画一个圆柱形\n";}
  void Erase() {cout<<"把圆柱形清除\n";}
};

void Make(Shape &S1) {S1.Draw();}
void Remove(Shape *pS) {pS->Erase();}

// ----主程式---------------------------
main()
{
  Circle   C1;
  Cylinder CyL;
  Triangle T2;
  Square   Sq3;

  cout << "T2 有 "
       << sizeof(T2)/sizeof(int)
       << " 个 int." << endl;
  cout << "CyL 有 "
       << sizeof(CyL)/sizeof(int)
       << " 个 int." << endl;
  cout << "“Make(C1))” : ";
  Make(C1);
  cout << "“Make(CyL))”: ";
  Make(CyL);
  cout << "“Make(T2))” : ";
  Make(T2);
  cout << "“Make(Sq3))”: ";
  Make(Sq3);
  cout << "执行 “pS=&C1”   之后: " << endl;
  Shape *pS=&C1;
  cout << "“Remove(pS)”: ";
  Remove(pS);
  cout << "执行 “pS=&CyL”  之后: " << endl;
  pS=&CyL;
  cout << "“Remove(pS)”: ";
  Remove(pS);
  cout << "执行 “pS=&T2”  之后: " << endl;
  pS=&T2;
  cout << "“Remove(pS)”: ";
  Remove(pS);
  cout << "执行 “pS=&Sq3”  之后: " << endl;
  pS=&Sq3;
  cout << "“Remove(pS)”: ";
  Remove(pS);
}