1． 不定式修饰表示心情状态的形容词表示原因，如：
　　He was grieved to hear that his old friend was seriously ill.

2． 不定式修饰一些形容词表示范围、情况，这类形容词主要有clever, comfortable,
　　considerate, cruel, difficult, easy, foolish, (un)fortunate, free, good, hard, interesting,
　　lucky, pleasant, proud, quick, right, rude, slow, (un)wise, wrong等，如：
　　You were foolish not to follow her advice.

　　上述的某些形容词（如easy, difficult, good, hard, interesting）作表语，其后的不定式
　　被视为省略了逻辑主语，因此不定式用主动形式表被动意思，如：
　　English is hard (for me) to learn. (不用to be learnt)
　　Mary is easy (by someone else) to deceive. (不用to be deceived)

　　修饰上述形容词的不定式如与句子主语呈动宾关系，不定式是不及物动词时要带介词，
　　但介词后不能再带宾语，如：
　　Alice is easy to get along with.(不能去掉with，也不能在with 后加her)

3． 不定式修饰形容词作宾语，这类形容词常见的有：(un)able, afraid, anxious, content,
　　determined, eager, (un)fit, impatient, ready, (un)willing, worthy等，如：
　　He is eager to become a policeman