I am studying with Advanced Grammar in Use now and have faced some grammar points that I can't understand and never seen and heard of it before.

Please help me out.

1. must have to

ex) I can't start the computer ,You must have to know a password

ex) John wasn't at home when I went round .He must have had to go out unexpectedly.

2.will have p.p

ex) As you will have noticed, he's got new glasses (rather thean -------- would have noticed ~~~~~)

ex) Most people won't have seen last night's lunar eclipse .(rather than ---- wouldn't have been ~~~)

I asked two ESL teachers and got a different answers .One said "I had never seen this grammar in my life and the other was like " Yes . those are right grammar .you can use it.

I am confused .
1 2
Hi,

Whoever wrote the question for # 1, he'd better to back to school to learn his grammar all over agian.

"Must" has about the same meaning as "have to".

I must go! It's getting late/

I hav eto go......

# 2- Future perfect tense is not commonly use because of its peculiar nature. If used incorrectly, as in the examples, it will sound and look horrible.

ex) As you will have noticed, he's got new glasses (rather thean -- would have noticed ~~) There is tense conflict in the context.

ex) Most people won't have seen last night's lunar eclipse .(rather than -- wouldn't have been ~~~)

2 problems: 1) wrong tense and you are right. 2) With the use of "would not have", there seems to be a causative or conditional clause missing from the sentence following "lunar eclipse".

i.e. I wouldn't have gone out with my friends last night had you called me earlier, The fact was, I did go out and you did not call. This is a past conditioanl context which is what you had. The second part is missing.

A final comment: you should stay away from the teacher who approved of the use of such grammar, and he should be banned from entering the classroom in my opinion. Emotion: stick out tongue
Anonymous1. must have to

ex) I can't start the computer ,You must have to know a password

ex) John wasn't at home when I went round .He must have had to go out unexpectedly.
It baffles me that an ESL teacher might claim never to have heard this sort of construction. To me, there is nothing terribly unusual about the way "must" has been used, and it is also perfectly OK to combine it with "have to".

Basically, "must" can be used in two different ways. One way is to show obligation or necessity. This is the usage that people generally learn first. However, this is not the way "must" has been used in your examples.

Another way "must" is used is to draw a conclusion. (The reason for your confusion probably lies in the fact that you're not familiar with this usage.) When "must" is used to draw a conclusion, the speaker knows, for example, that A and B are facts, and based on that information the speaker concludes that it is quite likely that C will therefore also be true. For example:

John has dark circles under his eyes and he has been yawning all afternoon. You might draw this conclusion:
"John must be tired."

And that is the way "must" is used in your examples. The difference is only that the structure is more complex in your examples.

I can't start the computer. You must have to know a password. =
It must be necessary for a person to know the password if that person wants to be able to start this computer. = Based on the fact that I cannot start the computer and the fact that I do not know the password, I draw the conclusion that you (i.e. people in general) need a password in order to start this computer.

John wasn't at home when I went round. He must have had to go out unexpectedly. =
I expected John to be at home, so I stopped by to visit. But he wasn't at home. Therefore, it must have been necessary for him to go out unexpectedly. = Based on the fact that I thought John would be home (but wasn't), I draw the conclusion that he had to go out unexpectedly.

This type of use of "must" is not at all unusual. It is used both in BE and in AmE.
http://dictionary.cambridge.org/define.asp?key=52646&dict=CALD
http://education.yahoo.com/reference/dictionary/entry/must (see definition 5)
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I am not the anon. who posted this question. But, Yankee, just wanted to thank you for the great explanation. It certainly added to my understanding of English.
Anon.: The sentences in No. 2 are very good English. (a) As you will have noticed = a very elegant way to say, "You have PROBABLY noticed that ....(b) Most people won't have seen = Most people PROBABLY didn't see ....
The other posters have all given you great advice. Here is something that may help you better understand "You must have to know a password." The modal is "must." "Have to" is not REALLY a modal. It is just a main verb + infinitive. So: You + MUST (modal) + have (main verb) + to know (infinitive) + a password (object). Here's another example: They did the job very badly. They MAY + have + to do + it + again. Thanks for your great question. It made all of us think more deeply.
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For this sleepy head just waking up, it took me a few seconds to sort out who is who.....

Yankee has given the "must" usage a very detailed expanation and needed no further elaboration.

But I am struck in an odd way by the last post which was drawing a parallel between"They MAY + have + to do + it + again" and "you must have to...". Although "must" and "may" are both modals but their meanings and tone are nearly contrary to each other. Must has a commanding implication, and a conclusive property. May implies options or possibility.

In my opinion, if this parallellism is validated as true, then one may as well consider the use of "He should ought to be able to fix the computer..." grammatical.Emotion: big smile
In the two below you have the must of logic and the have to of necessity (or obligation).

Changing must to must have (in the second example) makes the logical conclusion apply in past time. The addition of have forces have to to change to had to. Thus the word have functions very differently in these two expressions:

must -- have to

must have -- had to
AnonymousYou must | have to know a password.
It must be the case that you have to know a password. ~ The only possible conclusion is that it is necessary for you to know a password.
AnonymousHe must have | had to go out unexpectedly.
It must have been the case that he had to go out unexpectedly. ~ The only possible conclusion is that it was necessary for him to go out unexpectedly.
______

In the two below you have the will have of high probability or confident conjecture.
AnonymousAs you will have noticed ...
As you most likely have noticed ... / As you have almost certainly noticed ... / As, of course, you have noticed ...
AnonymousMost people won't have seen ...
In all likelihood, most people have not seen ... / It can be naturally supposed that most people haven't seen ... / It's not likely that many people have seen ...

CJ
dimsumexpressdrawing a parallel between"They MAY + have + to do + it + again" and "you must have to...". Although "must" and "may" are both modals but their meanings and tone are nearly contrary to each other.
The poster was focusing on the similarity of the structure, not the similarity of meaning. Emotion: smile

Thus, these have the same structure, but not the same meaning:

They MAY be crazy. (Maybe they're crazy.)

They MUST be crazy. (They are certainly crazy by my reckoning.)

Likewise:

You may have to flip this switch to get the machine started.
You must have to flip this switch to get the machine started.

(Maybe you have to flip the switch. / You certainly have to flip the switch as I see it.)

CJ
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