LCOM1920-T5G03

    list_node_t *p, *n;

    void *val;

};

list_node_t* (list_node_ctor)(list_node_t *p, list_node_t *n, void *val){

    list_node_t *ret = malloc(sizeof(list_node_t));

    if(ret == NULL) return NULL;

    ret->val = val;

    return ret;

}

    free(p);

}

list_node_t* (list_node_next)(const list_node_t *p){ return p->n; }

    list_node_t *end_;

    size_t sz;

};

    list_t *ret = malloc(sizeof(list_t));

    if(ret == NULL) return NULL;

    ret->sz = 0;

    ret->end_  ->p = ret->begin_;

    return ret;

}

    if(l == NULL) return 0;

    if(list_size(l) > 0) return 1;

    list_node_dtor(l->begin_);

    free(l);

    return 0;

}

    list_node_t *node = list_node_ctor(position->p, position, val);

    position->p->n = node;

    position->p    = node;

    ++l->sz;

    return node;

}

    position->p->n = position->n;

    position->n->p = position->p;

    void *ret = position->val;

void         (list_push_back)(list_t *l, void *val){

    list_insert(l, list_end(l), val);

}

    return list_node_val(list_begin(l));

}

void         (list_pop_front)(list_t *l){

    list_erase(l, list_begin(l));

}

    list_node_t *it = list_begin(l);

    while(it != list_end(l) && *list_node_val(it) != val){

        it = list_node_next(it);