/*
 *          File: list.cpp
 *        Author: Robert I. Pitts <rip@cs.bu.edu> 
 * Last Modified: Fall 2000
 *         Topic: Templates
 * -----------------------------------------------------
 *
 * This is the implementation for a linked list class.
 *
 */

#include <iostream.h>
#include "list.h"

/*
 * Constructor
 * -------------------------
 * List starts out empty (i.e., no nodes).
 */

List::List()
{
  head = NULL;
}

/* Destructor
 * -----------------------
 * This deallocates all memory associated with the list.
 */

List::~List()
{
  // Since removeFromEnd() deallocates memory for the
  // node it removes, let it do the work.  Inefficient if
  // removeFromEnd() is inefficient, but ok for now.

  while (head != NULL)
    removeFromEnd();
}

/*
 * Function: insertAtBeginning
 * -----------------------
 * Add an item to the beginning of the list.
 */

void List::insertAtBeginning(int item)
{
  Node *newNode = new Node;
  newNode->item = item;

  // NOW LINK THE NODE INTO THE LIST.

}

/*
 * Function: removeFromEnd
 * -----------------------
 * Remove the last node and return its item.  Since we
 * are only using a pointer to the beginning ("head"),
 * we have to do the inefficient thing and search for
 * the last node, maintaining a "previous" pointer.
 */

int List::removeFromEnd()
{
  if (head == NULL) {
    cerr << "can't remove from empty list" << endl;
    exit(1);  // Terminate program.
  } else {
    Node *removeNode = head;
    Node *prev = NULL;

    while (removeNode->next != NULL) {
      prev = removeNode;
      removeNode = removeNode->next;
    }

    // FOUND THE NODE TO REMOVE, DEALLOCATE IT, FIX
    // ANY LINKS IN THE LIST, AND THEN RETURN THE ITEM.

  }
}

/*
 * Function: isempty
 * -----------------------
 * Tells whether list is empty or not.
 */

bool List::isempty() const
{
  return head == NULL;
}