什么是过去将来完成进行时？
过去将来完成进行时是英语中的一种复合时态，用来描述在过去某个时间点之前已经开始并一直持续到另一个过去将来时间点的动作或状态，同时该动作将在该过去将来时间点之前完成。它结合了过去将来时、过去完成时和过去进行时的特点，强调在过去某一时间点开始并一直持续到另一个过去将来时间点的动作，并突出动作在过去将来时完成之前的持续性。以下是一些例子，展示了过去将来完成进行时的用法：
- 从过去到过去将来时间点一直持续的动作：
- By that time last year, I was going to have been studying for three months.（在去年的那个时间，我已经学习了三个月。）
- By the end of last month, they were going to have been working on the project for a while.（到上个月底，他们已经在做这个项目一段时间了。）
- 强调持续性和延续性：
- He was going to have been practicing the piano for weeks before the recital.（在演奏会之前，他已经练习了几周的钢琴。）
- They were going to have been traveling around the country for a long time before they settled down.（在安定下来之前，他们已经在全国各地旅行了很长时间。）
- 从过去某一点到过去将来时间点一直进行的状态：
- She was going to have been living in that city for years before she moved to another country.（在搬到另一个国家之前，她已经在那个城市住了好几年。）
- He was going to have been feeling unwell for days before he finally went to the doctor.（在最终去看医生之前，他已经感到不适好几天了。）
过去将来完成进行时强调从过去某一时间点开始，持续到另一个过去将来时间点的动作或状态，并突出动作在过去将来时完成之前的持续性
过去将来完成进行时的用法与将来完成进行时是一致的，但其立足的时间点是在过去。
* He said that by the end of the spring term he would have been studying English for three years.
他说到春季（即下）学期末，他将学了三年英语了。
* He told me that by the end of the year he would have been living there for thirty years.
他告诉我，到年底他在那里住了有30年了。
* Mr. Jackson decided to return to London next month. By that time he would have been working with us here for six years. 杰克逊先生决定下个月回伦敦。到那时他在这里就已和我们一起工作六年了。
