英语中有一种时态叫做“过去将来完成时”，也称为“将来的过去完成时”，表示在过去某一时间之前已经完成的动作。它的结构如下：
肯定句： 主语 + would + have + 过去分词
否定句： 主语 + would + not + have + 过去分词
疑问句： Would + 主语 + have + 过去分词 + 其他？
例如：
- By the end of next month, I would have finished my project.
- They would not have arrived by now.
- Would you have attended the meeting if you had known about it?
在日常生活中，我们可以用过去将来完成时来表达一些猜测或推测，比如：
- 对过去未知的情况进行猜测：
He would have been very happy if he had received your gift.（如果他收到了你的礼物，他一定很高兴。）
- 对过去已知的情况进行猜测：
She would have been very busy last night.（昨晚她一定很忙。）
- 对未来情况的猜测：
By this time next year, we would have moved to a new house.（到明年这个时候，我们一定搬到了新房子里。）
总之，过去将来完成时在英语语法中是一个非常重要的时态，它能够表达出我们对过去和未来的猜测和推测，能够帮助我们更好的理解和运用英语知识。
