be to + infinitive

Hello
Anyone can tell me the “be to + infinitive” ? Where do we use it ?

be
v.aux.
3. Used with the infinitive of a verb to express intention, obligation or future action: She was to call before she left. You are to make the necessary changes.

(TheFreeDictionary)

She was to call before she left.

Can i say “she would call before she left” ?

Hi Volcano

Why don’t you try to put your “would call” sentence into a context for us? A context in which you think a sentence with “was to call” could replace the “would call” sentence. That way we’ll be able to determine with more certainty whether you’ve understood the usage properly.

Of the the three options that Conchita mentioned (i.e. intention, obligation or future action), which one do you think your sentence with ‘would call’ illustrates?

Amy

Here are some sentences.Can you explain what their means ?

They are to be married soon
The Prime Minister is to make a further visit to Devon next week.
We are to receive a pay rise in line with inflation in September.
If we are to catch that train, we shall have to leave now.
He was to have appeared in the West End show but broke his collar bone during rehearsals.

Thank you

Hi Volcano

You cannot replace ‘be to’ with the word ‘would’ in any of your sentences. I’ve given you other ways of saying the same thing in your sentences:

They are to be married soon.
They plan to / intend to / are going to get married soon.

The Prime Minister is to make a further visit to Devon next week.
The PM intends to / is going to / is supposed to make a further visit to Devon next week.

We are to receive a pay rise in line with inflation in September.
We are going to / are supposed to receive a pay rise …

If we are to catch that train, we shall have to leave now.
If we are going to catch that train …

He was to have appeared in the West End show but broke his collar bone during rehearsals.
He was scheduled to / was supposed to have appeared in the West End show…

[b][i]

Thank you very much but i couldn’t understand the last sentence

“He was to have appeared in the West End show but broke his collar bone during rehearsals.”

Why it has “Perfect Tense” ? And what mean it gives in the sentence? [/i][/b]

Hi Volcano,
To emphasize that the action did not take place the perfect infinitive is used after the past indefinitie of the verb to be to

I see thanks