Thanks Alan! Actually the usage confused me in that context and now it’s clear. I understand when we use “you are not to…” it simply means “you shouldn’t or must not …”
We [color=red]have yet to decide what action to take (= We have not decided what action to take).
Can I say “are yet to” in place of [color=red]have yet to?
Authorities in Dalian [color=darkblue]are yet to assess the damage to the environment.
Is this sentence grammatically correct? Can I say “have yet to” instead of [color=darkblue]are yet to?
You were right with your earlier definition: we have not decided what action to take.
It is possible to use ‘We are yet to decide what action to take’ but as Alan has indicated, this loses some sense of immediacy when compared to ‘We have yet to decide what action to take.’.