C++ Linked list includes destructor

#include <iostream>
using namespace std;
struct link                           //one element of list
{
   int data;                          //data item
   link* next;                        //pointer to next link
};
class linklist                        //a list of links
{
   private:/*from w  w  w  .  j  a va 2s.  c  om*/
   link* first;                    //pointer to first link
   public:
   linklist()                      //no-argument constructor
   { first = NULL; }            //no first link
   ~linklist();                    //destructor
   void additem(int d);            //add data item (one link)
   void display();                 //display all links
};
void linklist::additem(int d)         //add data item
{
   link* newlink = new link;          //make a new link
   newlink->data = d;                 //give it data
   newlink->next = first;             //it points to next link
   first = newlink;                   //now first points to this
}
void linklist::display()              //display all links
{
   link* current = first;             //set ptr to first link
   while( current != NULL )           //quit on last link
   {
      cout << endl << current->data;  //print data
      current = current->next;        //move to next link
   }
}
linklist::~linklist()                 //destructor
{
   link* current = first;             //set ptr to first link
   while( current != NULL )           //quit on last link
   {
      link* temp = current;           //save ptr to this link
      current = current->next;        //get ptr to next link
      delete temp;                    //delete this link
   }
}
int main()
{
   linklist li;       //make linked list
   li.additem(25);    //add four items to list
   li.additem(36);
   li.additem(49);
   li.additem(64);
   li.display();      //display entire list
   cout << endl;
   return 0;
}