对将来进行假设主要有三种情况：
1,if条件从句是谓语用动词过去式,则后面的主句是情态动词加动词原形
例：If I came tomorrow ,we would have the meeting.
2,if条件从句是were to形式,则后面的主句也是情态动词加动词原形
例：If it were to rain tomorrow ,the meting would be put off.
3,if条件从句是should do形式,则后面的主句可以用情态动词加动词原形,也可以用祈使句（但注意,祈使句仅适用于前面从句是should do形式的）
例：If it should rain tomorrow,don't expect me./I would not go there.
扩展资料
对现在事实相反的虚拟语气
1、表示与现在事实相反的情况
从句：If+主语+动词一般过去时(Be动词用were)
主句：主语+ should/would/might/could+do：
If I were you，I would take an umbrella.
如果我是你，我会带把伞。（事实：我不可能是你）
If I knew his telephone number，I would tell you.
如果我知道他的电话号码，我就会告诉你。（事实：不知道）
If there were no air or water，there would be no living things on the earth.
如果没有水和空气，地球上就不会有生物。(事实：地球上既有空气也有水)
If I had any money with me，I could lend you some.
如果我带钱了，我就会借给你些。（事实：没有带钱）
If he studied harder，he might pass the exam.
如果他再努力些，就能通过考试了。（事实：没有努力）
If I were you， I'd wear a shirt and tie.
如果我是你，我就会穿衬衫和领带。(事实：我并不是你）
2、表示与过去事实相反的情况
从句：If+主语+had+done
主句：主语+should/would/might/could+have done
eg：If I had got there earlier，I should/would have met her.
如果我早到那儿，我就会见到她。（事实：去晚了）
If he had taken my advice，he would not have made such a mistake.
如果他听我的劝告的话，就不会犯这样的错误了。（事实：没有听我的话）
参考资料：百度百科-虚拟语气
与将来事实相反：若与将来事实相反，条件从句的谓语用过去式(be通常用were)，主句谓语用“should (would、could、might)+动词原形”。
如：If he went，would you go too?
如果他去，你也去吗?(大概他不会去)
If I asked him，I’m sure he’d help us.
如果我向他提出要求，肯定他会帮助我们。
扩展资料
虚拟语气可以采用倒装形式表示强调，因为害怕对方因为没有听清或者看清而引起误解。倒装的方法就是：去掉if，把助动词或be动词提到主语之前，变成疑问句语序。
比如：
1、If he were my friend, he would help me warm-heartedly.
Were he my friend, he would help me warm-heartedly.
倒装方法：去掉if，把be动词were提前，变成疑问句语序。
2、If the tools should arrive late, you could tell us immediately.
Should the tools arrive late, you could tell us immediately.
倒装方法：去掉if，把助动词should提前，变成疑问句语序。
3、If my brother had studied harder, he would not have failed the exam.
Had my brother studied harder, he would not have failed the exam.
倒装方法：去掉if，把助动词had提前，变成疑问句语序。
同时，还要注意，宾语从句、表语从句、同位语从句、主语从句也会出现虚拟语气。当主句中出现一个坚持（insist），两个命令（order，command），三个建议（suggest，advise，recommend）和四个要求（ask, require, demand, request）等词时。
从句谓语动词用(should) do/should have done的形式表示虚拟语气，其中should可省略。毕竟，即便我“坚持、建议、要求、命令”，对方也不一定照做，所以只能是虚拟语气。
本回答被网友采纳表示与将来事实相反的假设，对将来表示怀疑，或将来的动作不太可能实现时，条件状语从句和主句的谓语动词有以下形式：（见表）
条件状语从句的动词形式(三种)
主句的动词形式
(1) If + 主语 + 动词过去式 (be的过去式用were). 通常要与一个表示将来的时间状语连用. (2)If+主语(任何人称和数)+should+动词原形
(3)if+主语(任何人称和数)+were to+动词原形
I (we)should+动词原形
主语+would (might, could)+动词原形
例句：
·If it rained tomorrow, our picnic wouldbe put off.
·If it should rain tomorrow, our picnicwould be put off.
·If it were to rain tomorrow, our picnicwould be put off.
·If you should fail, what would you do?
·If I were to see her tomorrow, I wouldtell her the truth.
·If it were to rain tomorrow, the meetingwould be put off.
·I bet Brazil will win the World Cup. Ifit should lose, I would treat you a meal.
注意：当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，动词的形式要根据它所表示的时间来调整。
If you had worked hard, you would be very tired. (从句说的是过去，主句指的是现在。)
If he had followed the doctor’s advice, he would bequite all right now.
If I were you, I would have gone home.
Ifshe hadn’t trained so hard, she wouldn’t be able to run so fast.
智课网官方网址：http://www.smartstudy.com/本回答被网友采纳