The logic behind present perfect/infinitive + present perfect

Question

May I ask what the logic is behind using present perfect/infinitive + present perfect in "present perfect + since + present perfect" sentences?

it has been a while since I have enjoyed a party this much.

and

It's been a long time since I have read an interesting book.

Why is it not present perfect + past simple? I understand the "it's been" part, since it's something that is still relevant or going on. But if I'm referring to a specific past event, why should present perfect even be considered?

2) Also, I've seen people replace infinitive forms with present perfects:

"You must be surprised to receive a letter from me" = "You must be surprised to have received a letter from me"

Is there such thing as an infinitive present perfect? How is this construction possible?

Please help me understand!

Answer 1

It's been a long time since I have read an interesting book.

"Why is it not present perfect + past simple? I understand the "it's been" part, since it's something that is still relevant or going on. But if I'm referring to a specific past event, why should present perfect even be considered?"

I was reading your statement, and began thinking. And although Hellion is correct when he said:

"in both of the sample sentences, you're not referring to a specific past event, but to a somewhat generic experience; you can say "It's been a long time since I have read an interesting book", but you shouldn't say "It's been a long time since I have read The Hobbit".

He forgot a detail.

What if the last time I had read an interesting book was indeed at a specific past event, for example, last month? Hence a completed action, my reading an interesting book, at a definite time in the past.

Could a person then say:

"It's been a long time since I read (simple past) an interesting book."

I believe the answer is yes. It is grammatically correct and makes sense.

Here is another example taken verbatim from "A Practical English Grammar" (A.J.Thomson A.V.Martinet):

"I've worked here since I left school"

Which means I have finished attending school (for whatever reason but the most plausible being I have graduated or taken my final year exams) and now I am working i.e. I am not a student any more but currently an employee.

Answer 2

The logic behind the constructions given in point 1 is that the present perfect is being used to express an experience: at some point in the past, you had the experience of enjoying a party, or of reading an interesting book. Now, in the present, you are stating that it has been a long time since you experienced those things.

In both of the sample sentences, you're not referring to a specific past event, but to a somewhat generic experience; you can say "It's been a long time since I have read an interesting book", but you shouldn't say "It's been a long time since I have read The Hobbit".

For point 2, the present perfect is being used to describe a change of condition: at some point in the recent past you changed from the state of "no letter received" to "letter received". For the specific example given (surprise), I'm inclined to say that such a construction is wrong; surprise is a reaction to a current situation, so by definition, something that happened to you in the past (even the recent past) does not surprise you in the present.

On the other hand, for the general case, combining an expression regarding our current condition with information about what happened to cause it is entirely natural:

I have found $20 in my pocket. (present perfect: I found it just a few seconds or minutes ago)

I am happy because I have found $20 in my pocket. (simple present status, with present perfect cause of that status)

Other examples:

I am happy to have caught up with you.

We are sorry that you have decided to leave.

You must be proud that your son has been accepted to Yale.

Answer 3

1. Don't look for "logic" in this construction. It is a pattern dating back to at least the middle of the 17th century, a time when since was used in many more ways than it is today. John Dryden himself, one of the key figures in the 'rationalization' of English into its modern form, had no compunction about using both the simple past and past perfect form in the same sentence!

           … ’tis now three Years since I
   Have heard from him, and since I saw him twelve. - The Rival Ladies,1664

   The language has evolved since then, but this remains as a fossil. It's just the way (or one way) we say this.

2. Yes, the perfect infinitive, HAVE_INFINITIVE + past participle, is an established and completely noncontroversial construction. You use it, in fact, every time you compose an ordinary future perfect, which is formally will + [perfect infinitive]: I will have finished it by noon. There, to be sure, you use a 'bare' (unmarked) infinitive; but if instead of a full modal like will you use a verb which requires a marked infinitive the structure is clear: I plan to have finished it by noon.