Hi, everyone. I'm studying modals recently. I have a doubt about "ought to be doing". My grammar book says "ought to be doing" means "someone is not doing what he/she is supposed to do" in an affirmative sentence or "someone is doing what he/she isn't supposed to do" in an negative sentence. For example:

He ought not to be spending all his time on the TV. He should study for his exam.

We ought to be wearing seat belts, but we are not.

My question is: Does "ought to be doing" only has this meaning? Could it serve other function as well?

I hope you could tell me if there is any, thank you for your help!
It doesn't have to be comparing what we are doing to what we should be doing. "We ought to leave/to be leaving at 10" implies that we probably will leave by then, because of necessity.
Ought to means should.

Ought not to means should not
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You use should or ought to:
1 to say that you expect something to happen
He ought to be here soon.
2 to say that something is morally right
People ought to wear seat belts.
3 when you are giving someone advice
You ought to see a doctor.
 Philip's reply was promoted to an answer.
I agree with Philip. "Ought to' means 'should'?

They are interchangeable.
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