Page 287 - Practical English Usage 3ed - Michael Swan, Oxford

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infinitives (2): forms
Besides the ordinary infinitive (e.g. (to) go, (to) work), there are also
progressive, perfect and passive forms.
progressive infinitive: (to) be .. .ing
Like other progressive forms (see 470), progressive infinitives suggest that actions and events are I were I will be continuing around the time that we are talking about.
It's nice to be sitting here with you.
I noticed that he seemed to be smoking a lot. This time tomorrow I'll be lying on the beach.
(future progressive tense: see 220)
Why's she so late? She can't still be working.
perfect infinitive: (to) have + past participle
Perfect infinitives can have the same kind of meaning as perfect tenses (see 427) or past tenses (see 421-422).
It's nice to have finished work. (:;:: It's nice that I have finished.)
I'm sorry not to have come on Thursday. (= ... that I didn't come ...)
We often use perfect infinitives to talk about 'unreal' past events: things that did not happen, or that may not have happened (see 288).
I meant to have telephoned, but I forgot.
You should have told me you were coming.
I may have left my umbrella at the restaurant.
passive infinitive: (to) be + past participle
Passive infinitives have the same kind of meaning as other passive forms (see 412).
There's a lot ofwork to be done. She ought to be told about it.
That window must be repaired before tonight.
Sometimes active and passive infinitives can have similar meanings, especially after a noun or be (see 287).
There's a lot of work to do I to be done.
combinations
Perfect progressive and perfect passive infinitives are common.
I'd like to have been sitting there when she walked in.
They were lucky - they could have been killed. Progressive passive infinitives are possible but unusual.
What would you like to be doing right now? - I'd like to be being massaged. Progressive perfect passive infinitives (e.g. It must have been being built at the time) are very unusual.
negative forms
Negative infinitives are normally made by putting not before the infinitive. Try not to be late. (NOT USUALLY Try t6 116£ be /tile. OR Try £6 .:16;1'£ be /tile.) You were silly not to have locked your car.
He's very busy. I'm afraid he can't be disturbed.
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