if引导的非真实条件句

语法结构
1.if结构（非真实条件句——表示的是假设的或实际可能性不大的情况）

与..事实相反 If从句 主句
过去 Had done Would* have done
现在 Were/did Would* do
将来 Should do/were/were to do Would* do

例句：If there hadn’t been much rain in spring, we would have had a good harvest now. [过去]
If he smoked less, his cough might be well soon. [现在]
If the lecturer should be late, you would have to make a speech first. [将来]

备注：
（1）上表中’*’，would都可转换为should、could、might。
（2) 如果为时间错综句的话，左右两栏可互相搭配，排列组合。
例句：
He would still be alive today if he hadn’t taken that drug.
[与现在事实相反] [与过去事实相反]

(3) if可转换为其他形式
例句：Without your advice, our meeting wouldn’t have been so successfully. [过去]
（=>可转换为：If there hadn’t been your advice, we …）
Your notes are almost illegible (难以辨认的). Notes typed out would be a lot easier to read. [将来]
(=> 可转换为：If the notes had been typed out, it would be a lot easier to read.)
I should have