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

struct list_node
{
    struct list_node *prev, *next;
    int value;

    void init(int v) { value = v; }
    struct list_node *advance() { return next; }
};
struct list
{
    struct list_node *first, *last;

    struct list_node *begin() { return first; }
    struct list_node *end()   { return NULL; }

    void init() { first = NULL; last = NULL; }

    void insert(struct list_node *where, int v)
    {
        struct list_node *newnode = (struct list_node*)malloc(sizeof(*newnode));
        newnode->init(v);
        newnode->prev = where ? where->prev : last;
        newnode->next = where;
        if(newnode->prev)  newnode->prev->next = newnode;
        if(where) where->prev = newnode;
        if(where == first) first = newnode;
        if(!where) last = newnode;
    }
    void push_front(int v) { insert(begin(), v); }
    void push_back(int v)  { insert(end(), v); }
    void erase(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 == first) first = next;
        if(where == last) last = prev;
        free(where);
    }
    void clear() { while(first) erase(first); }
    void done() { clear(); }
};

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

    mylist.init();
    mylist.push_back(1);
    mylist.push_back(5);
    mylist.push_front(8);
    mylist.push_back(3);

    for(i = mylist.begin(); i != mylist.end(); i = i->advance())
        printf("%d ", i->value);
    printf("\n");

    mylist.done();

    return 0;
}