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I saw a sentence

She hoped to have done

Or a sentence, created with the same structure. I don'tunderstand how it works. Then I saw a full version of it:

She hoped that she had done

So, it's like a combination of Past Simple(hoped) + Past Perfect(had done) but combining them we can't have Past Perfect, we have only perfect infinitive.

When I later saw

She can't have done

I didn't understand it, too. Since then I've been trying to create a full version of it which would be clear for me. I tried

It can't be possible that she has done - I was told it was incorrect

It can't be true that she has done - I was told it was incorrect, too

I also have such variants:

It can't be real that she has done

There can't be a possibility that she has done it

There can't be a probability that she has done it

Is there any sentence among those I wrote which can be equaled to "She can't have done"?

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    The second phrase in the question is not a "full version" of the first phrase. They use different verb tenses in part, and they also have different meanings. Your question is far too broad. It's referencing a large number of different verb tenses and constructions, and then asking which is correct. As far as I can tell, the question boils down to this essentially: I don't understand the meaning of she can't have done. Most of the rest of the question can be stripped out. What is it about she can't have done that is confusing—and what do you mean when you say "full version"? Commented Jun 6, 2020 at 17:05
  • "She hoped to have done" is not the same as "She hoped that she had done"? But there's such an example - "He pretended to have lost her number and so had been unable to contact her. (or He pretended that he had lost her number …)" on dictionary.cambridge.org/grammar/british-grammar/…. It has the same structe I descriped - whether a short version (She hoped to have done = She hoped that she had done/He pretended to have lost = He pretended that he had lost) Commented Jun 6, 2020 at 17:21

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I think the main source of confusion is your idea of a "full version" of each phrase. As is mentioned in the comments, the second phrase isn't a "full version" of the first phrase. In fact, it's no more "full" than the first phrase.

Now, let's start at the beginning of your post. You claimed not to have understood the following:

She hoped to have done...

What you call the "full version," namely

She hoped that she had done...

has the same meaning. In your first example, the perfect infinitive just substitutes for the subordinate clause.

Now, to answer your question: can't is used in that context to imply that the speaker does not believe that it is possible that something happened. Let me use it in the present tense to show you what I mean. Let's say two people are having a conversation.

Person 1: Hey, do you know that the average cloud weighs 1.1 million pounds?

Person 2: No way! That can't be true.

What Person 2 is saying is:

Person 2: No way! I don't believe that it is possible that that is true.

Let's say that the people are talking about something that happened in the past.

Person 1: Hey, do you know that the guy who jumped from space fell at almost 1,400 kilometres per hour?

Person 2: No way! He can't have fallen that fast.

... where Person 2 is saying

Person 2: No way! I don't believe that it is possible that he fell that fast.

Hopefully this helps you.

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  • 1) Under full version I mean separating into tenses(She hoped-Past Simple that she had done-Past Perfect) just not to have everything mixed(She hoped to have done). 2) If "can't" means "The speaker does not believe that it is possible that something" then it can be the "full version" I mean. 3) "he can't have fallen that fast" - I don't understand this example because the context is about Past(jumped, fell), how can we use "can't" if it's supposed for Present? If to write a "full version" - "It can't be true that he fell/has fallen" - it'll be clear for me. Commented Jun 7, 2020 at 7:08
  • This case "can't" relates to something what I can't believe now but not to the jump itself because "can't" is present but jumping was in the past. Commented Jun 7, 2020 at 7:09
  • @MichaelAzarenko Modal verbs can sometimes be used for deduction. We use them when we want to express how certain we are as to whether something is true. Can't have [verb] is a construction that shows that the speaker does not believe that it is possible that something happened. It's a very specific case, which is why it may seem to go against what you previously learned about modal verbs. Here's a link that may help you: Modals – deductions about the past
    – Kman3
    Commented Jun 7, 2020 at 16:54
  • " the speaker does not believe that it is possible that something happened" - So, can I equal "She can't have done" to "I can't believe she did/has done it" and then to my original "It can't be real that she did/has done it"? Commented Jun 7, 2020 at 18:49
  • @MichaelAzarenko Your first example seems to suggest definitively that she did something: "can't have" doesn't share that level of certainty. Your original sentence is okay, but I would swap "real" for "possible".
    – Kman3
    Commented Jun 7, 2020 at 21:40

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