C++ Programming for Experienced Engineers/

...

/

SmartPointer that Iterates through a Container

SmartPointer that Iterates through a Container

Understand the implementation of a user-defined "SmartPointer" class that iterates through a linked list container.

We'll cover the following...

Problem

Write a program that maintains a linked list using a Container class. Also, implement a SmartPointer class that lets you access Container elements using the * operator and lets you iterate through the Container using the ++ operator.

Sample run

Here’s what you should see when you run the program.

10
20
0
-40
50

Coding solution

Here is a solution to the problem above.

C++
// Smart pointer to iterate through a container
#include <iostream>
class Container
{
	private :
		struct node
		{
			int data ;
			node *link ;
		} *head, *current ;
		int count ;
	public :
		Container( )
		{
			head = current = NULL ;
			count = 0 ;
		}
		void add ( int n )
		{
			node *temp = new node ;
			temp -> data = n ;
			temp -> link = NULL ;
			if ( head == NULL )
				head = current = temp ;
			else
			{
				node *q ;
				q = head ;
				while ( q -> link != NULL )
					q = q -> link ;
				q -> link = temp ;
			}
			count++ ;
		}
		int getcount( )
		{
			return count ;
		}
		friend class SmartPointer ;
} ;
class SmartPointer
{
	private :
		Container *cptr ;
	public :
		SmartPointer ( Container *t )
		{
			cptr = t ;
		}
		int operator *( )
		{
			if ( cptr->current == NULL )
				return 0 ;
			else
			{
				int i = cptr->current->data ;
				return i ;
			}
		}
		void operator ++ ( int n )
		{
			if ( cptr->current != NULL )
				cptr->current = cptr->current->link ;
		}
} ;
int main( )
{
	Container c ;
	c.add ( 10 ) ;
	c.add ( 20 ) ;
	c.add ( 0 ) ;
	c.add ( -40 ) ;
	c.add ( 50 ) ;
	SmartPointer sptr ( &c ) ;
	for ( int i = 0 ; i < c.getcount( ) ; i++ )
	{
		std :: cout << *sptr << std :: endl ;
		sptr++ ;
	}
	return 0 ;
}

Explanation

A container is a way to organize data in memory. Hence stacks, linked lists, arrays are all containers. An iterator is an object that moves through a container accessing various elements of the container. We can iterate through an ordinary C++ array by using ...