I have little confusion in traverse method

[BillyBob]

Did not get how we can assess private data by using dot ? As is happening in following code, please tell me, why is it ?


#include <iostream.h>
#include <stdlib.h>

using namespace std;

/* The Node class */
class Node
{
public:
int get() { return object; };

void set(int object) { this->object = object; };
Node * getNext() { return nextNode; };
void setNext(Node * nextNode) { this->nextNode = nextNode; };
private:
int object;
Node * nextNode;
};
/* The List class */
class List
{
public:
List();
void add (int addObject);
int get();
bool next();
friend void traverse(List list);
friend List addNodes();
private:
int size;
Node * headNode;
Node * currentNode;
Node * lastCurrentNode;
};
/* Constructor */
List::List()
{
headNode = new Node();
headNode->setNext(NULL);
currentNode = NULL;
lastCurrentNode = NULL;
size = 0;
}
/* add() class method */
void List::add (int addObject)
{
Node * newNode = new Node();
newNode->set(addObject);
if( currentNode != NULL )
{
newNode->setNext(currentNode->getNext());
currentNode->setNext( newNode );
lastCurrentNode = currentNode;
currentNode = newNode;

}
else
{
newNode->setNext(NULL);
headNode->setNext(newNode);
lastCurrentNode = headNode;
currentNode = newNode;
}
size ++;
}
/* get() class method */
int List::get()
{
if (currentNode != NULL)
return currentNode->get();

}
/* next() class method */
bool List::next()
{
if (currentNode == NULL) return false;
lastCurrentNode = currentNode;
currentNode = currentNode->getNext();
if (currentNode == NULL || size == 0)
return false;
else
return true;
}
/* Friend function to traverse linked list */
void traverse(List list)
{
Node* savedCurrentNode = list.currentNode;
list.currentNode = list.headNode;
for(int i = 1; list.next(); i++)
{
cout << "\n Element " << i << " " << list.get();
}
list.currentNode = savedCurrentNode;
}
/* Friend function to add Nodes into the list */
List addNodes()
{
List list;
list.add(2);
list.add(6);
list.add(8);
list.add(7);
list.add(1);
cout << "\n List size = " << list.size <<'\n';
return list;
}
main()
{
List list = addNodes();
traverse(list);
}

Now as you can see in traverse method we are assessing private data by dot, why compiler is not giving error ?

[coder777]

Due to the keyword friend. This allows the friend function to access private members.