將來完成時：

1.構成：shall / will have + 過去分詞

2.功能：表示將來某時之前已經(jīng)完成的動作。

→They will have been here for 5 years next Friday.

→By the end of next term, the students will have finished the book.

?

過去將來完成時：

1.構成：would / should have + 過去分詞

2.功能：表示從過去某個時間看將來某時之前已經(jīng)完成的動作。

→He said that they would have arrived by seven o'clock.

?

將來完成進行時：

1.構成：shall / will have been + 現(xiàn)在分詞

2.功能：表示某一動作將繼續(xù)到將來某時，且該動作此時尚未發(fā)生。

→We shall have been staying here for four weeks when Tom arrives.

→It will have been raining for a week if it does not stop tomorrow.

注：此句型過于復雜，人們很少運用，了解而已。