Practical Example of Using Virtual Functions II

From the past few articles we have been discussing about Virtual
Functions. Before taking up another topic for discussion I thought
of providing one more example of how and when virtual functions may be used.
So, here it is, a practical
example of virtual function.

As virtual functions and Run-Time
Polymorphism goes hand-in-hand so the example here may also serve as
an example of the use of run-time polymorphism.


  // Example to illustrate
  // the use of virtual functions
  // and run-time polymorphism
  #include <iostream.h>

  // -- SORT CLASS --
  class sort
  {
  protected:
    int *arr;
    int num_elmnt;

  public:
    sort(int);
    ~sort();
    void get_elmnt();
    void show_elmnt();
    virtual void do_sorting()=0;
  };

  // takes an argument
  // which is the number of
  // elements we want
  sort::sort(int x)
  {
    num_elmnt=x;
    arr=new int[num_elmnt];
  }

  sort::~sort()
  {
    // free up he allocated memory
    delete []arr;
  }

  void sort::get_elmnt()
  {
    // input elements
    cout<<"
Enter Elements...";
    for(int i=0;i<num_elmnt;i++)
    {
      cout<<"
#"<<i+1<<":";
      cin>>arr[i];
    }
  }

  void sort::show_elmnt()
  {
    // display the elements
    cout<<"
Elements are...";
    for(int i=0;i<num_elmnt;i++)
    {
      cout<<"
#"<<i+1<<":";
      cout<<arr[i];
    }
  }
  // -- SORT CLASS ENDS --

  // -- BUBBLE SORT CLASS --
  class bubble_sort : public sort
  {
  public:
    // constructor only calls the 
    // base constructor with the
    // parameter
    bubble_sort(int x):sort(x){}

    void do_sorting();
  };

  void bubble_sort::do_sorting()
  {
    int temp;

    // do bubble sorting
    for(int i=0;i<num_elmnt;i++)
      for(int j=0; j<(num_elmnt-1); j++)
        if (arr[j]>arr[j+1])
        {
          temp=arr[j];
          arr[j]=arr[j+1];
          arr[j+1]=temp;
        }
  }
  // -- BUBBLE SORT CLASS ENDS --

  // -- SELECTION SORT CLASS --
  class selctn_sort : public sort
  {
  public:
    // just call the base class
    // constructor
    selctn_sort(int x):sort(x){}
    void do_sorting();
  };

  void selctn_sort::do_sorting()
  {
    int temp;

    // do selection sorting
    for(int i=0;i<(num_elmnt-1);i++)
      for(int j=i+1;j<num_elmnt;j++)
      {
        if(arr[i]>arr[j])
        {
          temp=arr[i];
          arr[i]=arr[j];
          arr[j]=temp;
        }
      }
  };
  // -- SELECTION SORT CLASS ENDS --

  void main()
  {
    bubble_sort bubble(3);
    selctn_sort selctn(5);
    sort *ptr;

    ptr=&bubble;
    ptr->get_elmnt();
    ptr->do_sorting();

    ptr=&selctn;
    ptr->get_elmnt();
    ptr->do_sorting();

    // again point to bubble
    ptr=&bubble;
    ptr->show_elmnt();

    // again point to selctn
    ptr=&selctn;
    ptr->show_elmnt();
  }