void
list_print(list *l, void (*print_callback) (void *p))
{
    list *l1 = l;
    while(l1 != NULL) {
        print_callback(l1->data);
        l1 = l1->next;
    }
}
void console_print(const char *str)
 {
	if (print_callback) {
 		print_callback(str, print_callback_userdata);
	}
 }