I promised not to wake him up. 我答应了不叫醒他。

不定式句法功能

不定式可以作句子的主语、宾语、宾语补足语、表语、定语、状语等成分。

⒈ 作主语

如：To hear from you is nice.

To be a good teacher is not easy.

不定式作主语时，为了保持句子的平衡，往往以it作形式主语，而不定式置于谓语动词后。

如：It's nice to hear from you.

It's not easy to be a good teacher.

⒉ 作宾语

通常用于afford, agree, aim, arrange, ask, attempt, choose, continue, dare, decide, demand, desire, determine, expect, fail, hate, help, hesitate, hope, intend, learn, long, love, manage, mean, need, offer, plan, prefer, prepare, pretend, promise, prove, refuse, seek, threaten, trouble, wait, want, wish等动词后面。

如：I forgot to lock the door.

Please remember to write to me.

记忆口诀：

三个希望两答应（hope，wish，want，agree，promise）

一个要求莫拒绝（demand，refuse）

设法学会做决定（manage，decide）

不要假装在选择（pretend，choose）

⒊ 作表语

如：My job is to pick up letters.

He seemed to have heard nothing.

⒋ 作定语

在the first, the second, the third, the last等之后通常接不定式作定语。作定语时须放在被修饰的名词之后：

如：He is always the first one to get up.

I have a few words to say on this question.

主动形式表被动含义：

如：I have a book to read.

It is easy to read.

Have you anything to send?

比较：Have you anything to be sent?

She is the last to come.

He is looking for a room to live in.

There is nothing to worry about.