3.will/shall+不定式完成式

如果要表示将来某一时刻之前已完成的动作，便可采用“will/shall+have done”结构。

By the end of the chapter you will have guessed its meaning．(人教大纲版高三第206页)

当你读到这个章节的末尾时，你就猜出意思了。

If he can find the stained garment，he will have found the thief．(人教大纲版高三第113页)

如果他能找到这件沾有污迹的衣服，他就能找到这个贼了。

By this time next year George will have taken his university degree．

明年的这个时候乔治就会拿到大学学位了。

Before long he will have forgotten all about it．

不久他就会把这件事全忘了的。

The snow will have disappeared before the end of March．

雪在三月底前就会融化了。

提示：

will have done结构也可表示推测。

He will have received the letter by now．

这时他一定收到了我的来信．

所以The guests will have arrived．这个句子是有歧义的:

(1)客人们到时候就将到那里。(2)客人们想必已经到了。