Unit 25. When I do / When I've done When and if

Unit 25. When I do / When I've done When and if
(использование оборотов when I do, when I've done, when, if)

Study this example situation:

A: What time will you phone me tomorrow?
B: I'll phone you when I get home from work.

"I'll phone you when I get home from work" is a sentence with two parts:

and

the main part:
the when-part:

"I'll phone you"
"when I get home from work (tomorrow)"

The time in the sentence is future ("tomorrow") but we use a Present tense (get) in the when-part of the sentence.
We do not use will in the when-part of the sentence:

We'll go out when it stops raining. (not when it will stop)
When you are in London again, you must come and see us. (not when you will be)
(said to a child) What do you want to be when you grow up? (not will grow)

The same thing happens after: while before after as soon as until or till

I'm going to read a lot of books while I'm on holiday. (not while I will be)
I'm going back home on Sunday. Before I go, I'd like to visit the museum.
Wait here until (or till) I come back.

You can also use the Present Perfect (have done) after when / after / until / as soon as:

Can I borrow that book when you've finished it?
Don't say anything while lan is here. Wait until he has gone.

It is often possible to use the Present Simple or the Present Perfect:

I'll come as soon as I finish.
You'll feel better after you have something to eat.

or
or

I'll come as soon as I've finished.
You'll feel better after you've had something to eat.

But do not use the Present Perfect if two things happen together. The Present Perfect shows that one thing will be complete before the other (so the two things do not happen together). Compare:

When I've phoned Kate, we can have dinner.
(= First I'll phone Kate and after that we can have dinner.)
but
When I phone Kate this evening, I'll invite her to the party. (not when I've phoned)
(In this example, the two things happen together.)

After if, we normally use the Present Simple (if I do / if I see etc.) for the future:

It's raining hard. We'll get wet if we go out. (not if we will go)
Hurry up! If we don't hurry, we'll be late.

Compare when and if:
We use when for things which are sure to happen:

I'm going shopping this afternoon. (for sure) When I go shopping, I'll buy some food.

We use if (not when) for things that will possibly happen:

I might go shopping this afternoon. (it's possible) If I go shopping, I'll buy some food.
If it is raining this evening, I won't go out. (not when it is raining)
Don't worry if I'm late tonight. (not when I'm late)
If they don't come soon, I'm not going to wait. (not when they don't come)

See Unit 37. If I do … and If I did …
(использование оборотов If I do … и If I did …).
See Unit 38. If I knew … I wish I knew …
(использование оборотов If I knew … и I wish I knew …).
See Unit 39. If I had known … I wish I had known …
(использование оборотов If I had known … и I wish I had known …).
See Unit 111. Even
(использование even).
See Unit 114. As if
(использование оборота As if).

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Unit 25. When I do / When I've done When and if (использование оборотов when I do, when I've done, when, if)

Unit 25. When I do / When I've done When and if
(использование оборотов when I do, when I've done, when, if)