Читать книгу Plain English - Marian Wharton - Страница 49

127. We find also that we need a verb phrase to express time before some other future time, to describe an action that will be finished, perfected, or completed, before some other future action. Thus,

I shall have gone before you arrive.

You will have earned your money before you get it.

I shall have worked thirty days when pay-day comes.

Can you not see a difference in saying, I shall work thirty days when pay-day comes, and I shall have worked thirty days when pay-day comes? The first sentence expresses simple future time, or what you will do when pay-day comes; the second describes an action which will be completed or perfected before pay-day comes. So there is quite a difference in the meaning of the future and the future perfect time.

128. The future perfect time form expresses or describes an action that will be perfected or completed before some other future time. It is formed by using shall have or will have with the past participle.

Be careful to use the past participle. Never use the past time form with shall have or will have.