///////     File :  List.h    ///////
//  linked list objects
#ifndef List_SEEN__
#define List_SEEN__

#include <iostream.h>

class ListCell
{ friend class List;
  private:
    char item;
    ListCell* next;
    ListCell(char c = '\0', ListCell* ptr = NULL)
    :  item(c), next(ptr) { }   // constructor
};


class List
{ public:
    List() : head(NULL) { }            // empty list constructor 
    List(char c)                       // list with first cell
    : head (new ListCell(c,NULL)) { }
    ListCell* first() { return head; } // first cell
    ListCell* last();                  // last cell
    ListCell* find(char c);            // first item == c
    int substitute(char r, char s);    // r for first s on list
    int remove(char c);                // c from entire list
    void remove(ListCell* cell);       // remove given cell
    int shorten(int n);                // remove first n cells
    int put_on(char c);                // insert in front
    int insert(char c, ListCell* cell);// insert after cell
    int append(char c)                 // insert at end
    { return insert(c, last()); }
    int is_empty() { return(head == NULL); }
    void display(ListCell* p);         // display from p to end
    void display() { display(head); }  // display whole list
    ~List();                           // destructor
  private:
    ListCell* head;                    // first cell of list
    void free();                    // free all cells
};
#endif