//------------------- list2.h ---------------------------
//------------ header file for unit list ----------------

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//							 
//	C++ call by reference was used.			 
//	in order to succeed compelation, program file	 
//	must be save as cpp files.			 
//							 
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/ 

//-------------------- Types & definitions ----------------------------

typedef int list_info_type;   /* or anyt ather data type */

struct link_type
{
	list_info_type info;
	struct link_type *next;
};

typedef struct link_type *pos_type;

typedef struct
{
	pos_type anchor;
	/* more  fields  if  needed */
} list_type;

//----------------------- Prototypes ----------------------------------

list_type list_init (void);

pos_type list_anchor (list_type list);

pos_type list_end (list_type list);

pos_type list_next (list_type list, pos_type pos);

pos_type list_prev(list_type list, pos_type pos);

void list_insert (list_type &list, pos_type pos, list_info_type x);

void list_delete (list_type &list, pos_type &pos);

list_info_type list_retrieve (list_type list, pos_type pos);

int list_is_empty (list_type list);

void list_update (list_type &list, pos_type pos, list_info_type x);