should have done与shouldn't have done可以对比着理解
should have done表示应该做但实际没做
shouldn't have done表示不应该做但实际做了
如：He should have known that the police would never allow this sort of thing. 他本该知道警察决不会允许这类事情的发生.
He shouldn't have known this. 他本不该知道这个
should have done 本应做某事却没做 I should have writen to you,but Ireally have no time.
should have done 本应做某事却没做
should have done =ought to have done 意思是过去本应该做而没做，隐含指责的对方的意思。 You should have told me that earlier. 其实你没有早点告诉我。
should have done常与must have done相比较 should have done是过去做而没有作I should have done better in the exam 我本该在考试中做得很好，但是实际却没有 must have done是过去一定做了某事 He must have been in the street,because I saw him yesterday in the street!
答：should have done 表示假设， 过去应该做而没有做含有责备的意思。 如; You should have done your home work ...详情>>
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