/*
 * Simple C++ list of integers.  Everything is in one file for
 * simplicity of presentation.
 */

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

class IntegerList;

/*
 * Each element of the integer list (IntegerList::Element) consists of
 * a value and a pointer to the next element.  The head of the list is
 * represented by the IntegerList class itself, which is the only
 * thing visible from the outside.
 */
class IntegerList
    {
    public:
			IntegerList();
			~IntegerList();
	void		push(int newValue);	// Add a value to list
	int		pop();			// Take a value off list
    private:
	/*
	 * Auxiliary subclass that holds the actual data
	 */
	class Element
	    {
		friend	IntegerList;		// List class does all work
	    private:
			Element(int value_ = 0, Element* next_ = NULL);
			~Element();
		Element*
			next;			// Next element in list
		int	value;			// Value stored
	    };
	/*
	 * Private data
	 */
	Element*	head;			// First element in the list
    };

int main(					// Test IntegerList
    int			argc,			// Argument count
    char*		argv[])			// Arguments
    {
    IntegerList values;
    for (int i = 1;  i < argc;  i++)
	values.push(atoi(argv[i]));
    for (int i = 1;  i < argc;  i++)
	cout << values.pop() << endl;
    return 0;
    }

IntegerList::IntegerList()
    : head(NULL)
    {
    }

IntegerList::~IntegerList()
    {
    /*
     * Delete all of the elements stored in the list
     */
    while (head != NULL)
	{
	Element* nextElement = head->next;
	delete head;
	head = nextElement;
	}
    }

void IntegerList::push(				// Push onto head of list
    int			newValue)		// Value to push
    {
    Element* newCell = new Element;
    newCell->value = newValue;
    newCell->next = head;
    head = newCell;
    }

int IntegerList::pop()				// Return & remove list head
    {
    int result = head->value;			// Segfaults if empty!
    Element* disappearingCell = head;		// Save for deletion
    head = head->next;				// Remove list head
    delete disappearingCell;			// ..and return the memory
    return result;
    }

IntegerList::Element::Element(
    int			value_,			// Value to store in list
    Element*		next_)			// Next Element on list
    : next(next_),
      value(value_)
    {
    }

IntegerList::Element::~Element()
    {
    }