3. 不定式的完成式
当不定式的动作发生在谓语动词的动作之前，不定式要用完成式，在句中可作宾语，状语以及构成复合宾语，复合谓语。
She seemed to have heard about the news already。
He was believed to have been a very rich man。
4. 不定式的完成被动式
当不定式的逻辑主语是这个不定式所表示的动作的承受者，且不定式的动作发生在谓语动词的动作之前，不定式要用完成被动式，在句中可作主语，宾语或构成复合宾语，复合谓语。
The forest fire is reported to have been put out last night。
It is supposed to have been finished without referring to any reference books。
5. 带逻辑主语的不定式短语
不定式可以有逻辑主语，其构成形式为“for +代词的宾格(或名词) +不定式”。 带逻辑主语的不定式短语可在句子中作主语、宾语、表语或状语等。
It is not easy for you to catch up with them in a short time。
I think it better for you to see the doctor。
What we want is for you to understand the matter clearly。
I sent him some pictures for him to see what Paris is like。