不定式结构表达虚拟语气

不定时结构有时可用来表达虚拟语气，常见结构如下：

1. be to have done sth.表示曾希望或计划要做的事没有做成

I was to have mailed this letter, but I forgot to do so.我本想把这封信寄出去，但是我忘记了。

I meant to have telephoned, but I forgot.我本想打电话，但是忘记打了。

They expected you to have been here.他们原来估计你回来。

I was to have started work last week, but I caught a bad cold.我本来打算上星期就开始工作，可我患了感冒。（其实并没有开始工作）

He was to have employed you, but later he changed his mind.他本来打算聘用你的，可后来又改变了主意。

--Tom, did Mr Li join you in your discussion?

--No, he was to have, but he happened to have fallen ill.

2.某些动词 did to have done sth.表示过去未完成的动作

They wanted to have helped but couldn’t get here in time.他们本想来帮忙的，但没能及时到达这里。

I meant to have called on you but was prevented from doing so.我本打算去拜访你的，但确因有事没去成。

I planned to have finished the work ahead of time. 我原计划提前完成这项任务。

3.had done to do sth. 表示过去未完成的动作

They had wanted to help but couldn’t get here in time.他们本来是要来帮忙的，但因故未能来成。

I had intended to call on you but was prevented from doing so.我本来想去看你，但有事没去成。

I had wanted to help you with your homework but I couldn’t spare any time. I was writing a composition last night and I’ll finish it today.

一些表示心理状态的动词如： wish, want、intend、hope、mean、plan、expect, promise, suppose, wish, suppose, think, desire, be, would like, should like, be going to等等，用其过去完成时加不定式或者用一般过去时加不定式的完成式（在口语中用一般过去时加不定式的一般式表示希望、打算或意图未曾实现）

We intended to have gone to England this summer.

= We had intended to go to England this summer.