Method add_front

Kernel/include/list.h:111–122

	}

	void add_front(const T& obj) {
		if (!back) {
			back = obj;
		}
		else if(front) {
			front->prev = obj;
			obj->next = front;
		}
		front = obj;
		obj->prev = back;
		num++;
	}

	T operator[](unsigned pos) {
		return get_at(pos);