time clauses - present perfect

[Lenka]

I don't understand when present perfect tense can and can not be used in time clauses.

I've done some exercise from "English Grammar in Use" (R. Murphy) and I don't understand why present tense sometimes is and on the other hand, sometimes isn't used.

1) It's going to start raining. Let's go home before that. => Let's go home before it starts raining. ( NOT!!! ...has started raining. -why?)

2) Would you like a cup of tea before you go / leave? (NOT ...you've left? - why?)

[riverkid]

Originally Posted by Lenka

I don't understand when present perfect tense can and can not be used in time clauses.

I've done some exercise from "English Grammar in Use" (R. Murphy) and I don't understand why present tense sometimes is and on the other hand, sometimes isn't used.

1) It's going to start raining. Let's go home before that. => Let's go home before it starts raining. ( NOT!!! ...has started raining. -why?)

2) Would you like a cup of tea before you go / leave? (NOT ...you've left? - why?)

Lenka, we tend to use present simple for things that have become "scheduled".

[Lenka]

Originally Posted by riverkid

Lenka, we tend to use present simple for things that have become "scheduled".

I don't think I can understand it...

What about the following sentences? Has it become "sheduled"?? It is said it can be used both with present simple and present perfect.

I won't speak to her until she apologises (has apologised) to me.

I'll give you my address when I find (have found) somewhere to live.

I think it will be better when they finish (have finished/have built) the new road.

etc.


I can see absolutely no difference between the two sentences in my previous message and these three ones. However, there must be some, obviously.

[Mariner]

I won't speak to her until she apologises to me.

I'll give you my address when I find somewhere to live.

I think it will be better when they finish the new road.

All of these sentences include a main clause where the modal will is present, and a subordinate clause with the verb in the present tense. This is a very normal way to form these sentences.

*We will call him when you will come
We will call him when you come

[Filip Lund]

The Present Simple in the sentences you quoted refers to the future, has future connotation whereas The Present Perfect implies some association with the past. Time clauses after WHEN, BEFORE, AS SOON AS, very much the same as in the 1st conditional require The Present Simple since their primary time reference is that to the future.

[riverkid]

Originally Posted by Lenka

I don't think I [can] understand it...

What about the following sentences? Has it become "sheduled"?? It is said it can be used both with present simple and present perfect.

I won't speak to her until she apologises (has apologised) to me.

I'll give you my address when I find (have found) somewhere to live.

I think it will be better when they finish (have finished/have built) the new road.

etc.

Lenka's first two examples:

I can see absolutely no difference between the two sentences in my previous message and these three ones. However, there must be some, obviously.

1) It's going to start raining. Let's go home before that. => Let's go home before it starts raining. ( NOT!!! ...has started raining. -why?)

2) Would you like a cup of tea before you go / leave? (NOT ...you've left?

I knew that my answer wasn't quite up to snuff, Lenka.

But still, I think there is some measure to it. I think your first two sentences and your last three are different. Both going home and raining are reasonably expected, the people may even know when, rain in the afternoon and leaving soon.

The time frame for the other three is much more tenuous, more in the distant future but note that either the present simple or the present perfect works for those situations. It doesn't sound natural for the rain and leaving situations.

Why not devise some more examples and put in what you consider to be acceptable? That way one of us may be able to see thru the mystery. Good luck!

[Humble]

Hi, Lenka,
Yours is a good question. I think we use the Present Perfect in conditional clauses when it's presumed the action requires some time to be done or completed, it implies some process.
... until she has apologized.
So she hasn't done it yet and it will probably take her some time to realize she must do it. Here the process is her getting to understand that she was wrong or that apologizing is necessary.
I will only say the thing is lost after I have looked in every corner.
It'll take time to look in every corner.
To leave, to start raining are abrupt actions, so they require the Present simple.
I think already could be a test-word - if you can mentally insert it, then the Present Perfect is possible.
... until she has already apologized.
... before you have already left -sounds weird.

Regards

[Lenka]

I know what the reason of not using present perfect in the sentences is already.
The (shall I use the definite article here, by the way?) present perfect tense can be used only with the following prepositions:when, after, until, as soon as. => but not "before"!!

I'll come as soon as I've finished it. => You have finished it first and after that you'll come. (correct me if I've made any mistakes in my English, please!)

Let's go home before it starts (not "it has started") raining. => We'll go home and after that it will probably start raining. It isn't supposed that it has started raining and after that we'll go home...

[riverkid]

[quote=Lenka;136683]I know what the reason of not using present perfect in the sentences is already.
The (shall I use the definite article here, by the way?) either would work present perfect tense can be used only with the following prepositions:when, after, until, as soon as. => but not "before"!!

I'll come as soon as I've finished it. => You have finished it first and after that you'll come. (correct me if I've made any mistakes in my English, please!)

Why not 'before', Lenka?

Okay, I'll come before I've finished it.

It's not the norm, of course, but in certain circumstances, it's possible.



Let's go home before it starts (not "it has started") raining. => We'll go home and after that it will probably start raining. It isn't supposed that it has started raining and after that we'll go home...

Consider a situation where someone always waits too long and gets caught in the rain. Another person, being a wee bit or a lot strident, commenting on such a situation, could well use the present perfect;

This time, why don't we go home [OR] let's go home BEFOOORE it has started raining.

[Lenka]

[quote=riverkid;136723]

Originally Posted by Lenka

I know what the reason of not using present perfect in the sentences is already.
The (shall I use the definite article here, by the way?) either would work present perfect tense can be used only with the following prepositions:when, after, until, as soon as. => but not "before"!!

I'll come as soon as I've finished it. => You have finished it first and after that you'll come. (correct me if I've made any mistakes in my English, please!)

Consider a situation where someone always waits too long and gets caught in the rain. Another person, being a wee bit or a lot strident, commenting on such a situation, could well use the present perfect;

This time, why don't we go home [OR] let's go home BEFOOORE it has started raining.

Hmmm... Thanks for your reply... I didn't know it before! :)