#include <stdio.h>
#include <stdlib.h>

struct list_node
{
    struct list_node *prev, *next;
    int value;
};
struct list
{
    struct list_node *first, *last;
};

void list_node_init(struct list_node *n, int v) { n->value = v; }
struct list_node *list_advance(struct list_node *i) { return i->next; }
struct list_node *list_begin(struct list *l)        { return l->first; }
struct list_node *list_end(struct list *l)          { return NULL; }

void list_init(struct list *l) { l->first = NULL; l->last = NULL; }

void list_insert(struct list *l, struct list_node *where, int v)
{
    struct list_node *newnode = (struct list_node*)malloc(sizeof(*newnode));
    list_node_init(newnode, v);
    newnode->prev = where ? where->prev : l->last;
    newnode->next = where;
    if(newnode->prev)  newnode->prev->next = newnode;
    if(where) where->prev = newnode;
    if(where == l->first) l->first = newnode;
    if(!where) l->last = newnode;
}
void list_push_front(struct list *l, int v) { list_insert(l,list_begin(l), v); }
void list_push_back(struct list *l, int v)  { list_insert(l,list_end(l),   v); }
void list_erase(struct list *l, struct list_node *where)
{
    struct list_node* prev = where->prev;
    struct list_node* next = where->next;
    if(prev) prev->next = next;
    if(next) next->prev = prev;
    if(where == l->first) l->first = next;
    if(where == l->last) l->last = prev;
    free(where);
}
void list_clear(struct list *l) { while(l->first) list_erase(l, l->first); }
void list_done(struct list *l) { list_clear(l); }

int main(void)
{
    struct list mylist;
    struct list_node *i;

    list_init(&mylist);
    list_push_back(&mylist, 1);
    list_push_back(&mylist, 5);
    list_push_front(&mylist, 8);
    list_push_back(&mylist, 3);

    for(i = list_begin(&mylist); i != list_end(&mylist); i = list_advance(i))
        printf("%d ", i->value);
    printf("\n");

    list_done(&mylist);

    return 0;
}