#ifndef _LIST_H

struct node;
typedef struct node *node_ptr;
typedef node_ptr list;
typedef node_ptr position;

/* elem to int */
typedef int elem;

list make_empty(list header);
int is_empty(list header);
int is_last(position p, list header);
position find(elem x, list header);
void delete(elem x, list header);
position find_previous(elem x, list header);
void insert(elem x, list header, position p);
void delete_list(list header);
position header(list header);
position first(list header);
position advance(position p);

#endif    /* _LIST_H */