namespace C6
{

    class ListHead<T>
    {
        private ListHead<T> next;
        private ListHead<T> prev;
        private T data;

        public T GetData()
        {
            return this.data;
        }

        public void Del()
        {
            this.next.prev = this.prev;
            this.prev.next = this.next;
        }

        public void AddTail(ListHead<T> pnew)
        {
            var prev = this.prev;
            var next = this;

            next.prev = pnew;
            pnew.next = next;
            pnew.prev = prev;
            prev.next = pnew;
        }

        public void AddHead(ListHead<T> pnew)
        {
            var prev = this;
            var next = this.prev;

            next.prev = pnew;
            pnew.next = next;
            pnew.prev = prev;
            prev.next = pnew;
        }

    }

}