有一读者问： 动词不定式的完成式与现在分词的完成式可否用作定语？
动词不定式完成时态用作定语的情况并不罕见，详参见以下例句的划线部分：
(1)It's an awful thing to have happened .
(2)There is no need to have bought it .
(3)He had the good fortune to have studied with Professor Li.
但现在分词的完成时态一般则不能用作定语，虽然偶尔也有例外，如一些语法家所举的:
(4)Any man having witnessed the attack is under suspicion.
