#ifndef _DLLIST_H_
#define _DLLIST_H_

template <class Object>
class dList;                     // Forward reference to a dList

template <class Object>
class dlNode {
  friend class dList<Object>;    // dList should be able to use and inspect
                                 // dList_node's protected members and methods
 protected:
    dlNode();
    dlNode(Object val);
    ~dlNode();

    Object value;
    dlNode *flink;               // pointer to the next node in the list
    dlNode *blink;               // pointer to the previous node in the list
};

template <class Object>
class dList {
  public:
    dList();                      // initializes the dList
    dList(Object default_value);  // initializes the dList
    ~dList();                     // destroys the dList's nodes

    void insertBeforeCursor(Object value); // inserts the value before the node
                                         // pointed to by the list cursor
    void insertAfterCursor(Object value); // inserts the value after the node
                                        // pointed to by the list cursor
    void append(Object value);      // appends the value to the end of the list
    void prepend(Object value);     // appends the value to the front of the list

    void next();               // moves the list cursor to the next 
                               // element in the list
    void prev();	       // moves the list cursor to the previous
                               // element in the list
    bool endOfList();          // true if the list cursor points to the 
                               // sentinel node; false otherwise
    // If the list is empty, the following two operations make the
    // list cursor point to the list's sentinel node
    void first();             // resets the list cursor to the first
                              // element in the list. 
    void last();              // resets the list cursor to the last
                              // element in the list

    Object get();               // returns the value of the node pointed to
                              // by the list cursor

    void set(Object val);     // sets the current node to the indicated value

    void deleteNode();        // deletes the node pointed to by the list cursor
                              // and advances the list cursor to the next
			      // list element
    bool isEmpty();           // returns whether the list is empty

    // set the value in the sentinel node
    void setSentinelValue(Object value) { 
      sentinel_node->value = value;
    }

  protected:
    dlNode<Object> *cursor;           // the list cursor
    dlNode<Object> *sentinel_node;     // a pointer to the sentinel node
};

/* Traverse, where list is a (dList *) */
#define dl_traverse(list) \
  for((list)->first(); !(list)->endOfList(); (list)->next())
 
#define dl_rtraverse(list) \
  for((list)->last(); !(list)->endOfList(); (list)->prev())

#include "dList.cpp"

#endif