///////     File :  NList.h    ///////
//  nested list objects
#ifndef Nlist_SEEN__
#define Nlist_SEEN__
#include <iostream.h>

class NItem
{ friend class NList;
  private:
    enum Boolean {FALSE, TRUE};
    union
    {   char    ch;
        NItem*  lis;
    };
    Boolean l_c;  // 0 for list 1 for char
    NItem* next;
    NItem(char c = '\0', NItem* ptr = NULL)
    :  l_c(TRUE), ch(c), next(ptr) { }     // constructor
    NItem(NItem* l = NULL, NItem* ptr = NULL)
    :  l_c(FALSE), lis(l), next(ptr) { }   // constructor
};


class NList
{ public:
    NList() : head(NULL) { }           // empty list constructor 
    NList(char c)                      // list with first cell
    : head (new NItem(c,NULL)) { }
    int put_on(char c);                // put on a char
    int put_on(NList& c);              // put on a nested list
    void display(NItem* p, int r = 0); // display from p to end
    void display() { display(head); }  // display whole list
    /*   ...  */
  private:
    NItem* head;                       // first cell of list
    void free();                    // free all cells
};
#endif