形式

should / would have done sth.

用法

1、 過去將來完成時表示在過去將來某一時間以前發生的動作，并往往會對過去將來某一時間產生影響。

I thought you’d have left by this time. 我想這會兒你已經走了。

He told them he would have finished it by 8 o’clock. 他告訴他們他會在8點以前干完。

I guessed that Helen would have told her something. 我猜海倫會告訴她一些情況的。

2、 過去將來完成時還常用在虛擬語氣中，表示與過去的事實相反。