GUIDE ENGLISH GRAMMAR BOOK

PAGE 339
259 If, as long as, unless, in case etc
259 If, as long as, unless, in case etc
1 If and when
If the doctor comes, can you let her in? (The doctor might come.)
When the doctor comes, can you let her in? (The doctor will come.)
We use if (not when) for an unreal condition.
If I could see into the future, I'd know what to do.
(I can't see into the future.)
But in some contexts we can use either if or when. • 257(2a)
2 Short clauses
We can use a short clause with if but without a verb.
I'd like a room facing the street if (that is) possible.
If (you are) in difficulty, ring this number.
For if so and if not, • 43(3e).
3 Then
After an if-clause we can use then in the main clause.
If the figures don't add up, (then) we must have made a mistake.
If no one else has requested the book, (then) you can renew it.
4 As long as, provided etc
As well as if, we can also use as/so long as and provided/providing (that) to express
a condition.
You can renew a book in writing as long as/so long as you give its number.
I don't mind you using my bike provided (that) you take care of it.
We are willing to accept your offer providing (that) payment is made within
seven days.
Provided/Providing (that) is a little formal.
NOTE
a On condition that is formal.
We are willing to accept your offer on condition that payment is made within seven days.
b We can use the adverbial in that case (= if that is so).
I've lost my timetable. ~ Well, in that case I'll give you another one.
c We can use the prepositions in case of and in the event of.
In case of difficulty, ring this number. (= If you have any difficulty,...)
The prepositions with, without and but for can also express a condition.
With a bit more time, we could do a proper job. (= If we had a bit more time,...)
But for the climate, Edinburgh would be a perfect place to live.
5 What if and suppose/supposing
After a conditional clause with these expressions, there is often no main clause.
What if the tickets don't get here in time?
Suppose/Supposing there's nowhere to park?