//  File: list6.h
//
//  Another simple linked list ADT in C++.
//  This one uses more C++ "features"


#ifndef _list6_h
#define _list6_h

// ***Important: ListItem class is defined in the header file
// that is included in "listitem.h"

#include "listitem.h"


// Each node in the linked list is a ListNode object

class ListNode {
   friend class List ;

public:
   ListItem item ;              // data member

private:
   ListNode *next ;             // pointer to next node in the linked list
   ListNode() ;                 // default constructor
   ListNode(const ListItem&) ;  // alternate constructor
   ~ListNode() ;                // destructor
} ;


// Position in the linked list is a pointer to the node prior to
// the node of interest.

typedef ListNode *position ;


class List {
public:
   List() ;                         // default constructor
   ~List() ;                        // destructor
   void Append(const ListItem&) ;   // Add item to the end of the list
   void Prepend(const ListItem&) ;  // Add item to the beginning of the list
   void Delete(position) ;          // Remove node at given position
   int IsMember(const ListItem&) ;  // Item on the list? 0=No 1=Yes
   void Concatenate(List *) ;       // Add list to the end of this one
   List *Duplicate() ;              // Return copy of this list
   void Print() ;                   // Print the contents of this list
   int Count() ;                    // Return number of items in this list

   // The following 3 functions return copies of the items
   ListItem *FirstItem() ;          // First item on the list
   ListItem *LastItem() ;           // Last item on the list
   ListItem *ItemAt(position) ;     // Return item at given position

   // See documentation on meaning of position
   position FirstPos() ;                // Position of the first item
   position NextPos(position) ;         // Position after the given one
   position Locate(const ListItem&) ;   // Position of item on list.

protected:
   ListNode header ;
   int count ;
   ListNode *last ;
} ;

#endif