7-3. Причастные -ing клозы

Та же идея замены применима и в остальных случаях.

When you are writing a business letter, begin 'Dear Sir'.
When writing a business letter, begin 'Dear Sir'.

After he was in the army, he was an engineer.
After being in the army, he was an engineer.

While I am not optimistic I have not given up all hope.
While not being optimistic I have not given up all hope.

The people who are sitting here in the sun are tourists.
The people sitting here in the sun are tourists.

Will anyone who wants a ticket please apply to me.
Will anyone wanting a ticket please apply to me.

The boys who have shouted/who have been shouting the loudest are the winners.
The boys the loudest are the winners.

The boys who has shouted/who had been shouting/who shouted/who were shouting the loudest were the winners.
The boys shouting the loudest were the winners.

We have sat here in the sun for two hours and are very thirsty
Having sat here in the sun for two hours, we are very thirsty.