Those who failed to get in need not have felt disappointed,as many of the artistes who should have appeared did not come

Those who failed to get in need not have felt disappointed,as many of the artistes who should have appeared did not come
need not have felt和should have appeared这两段 他为什么要用现在完成时态呢?
因为need not have done结构表示【本来不必做某事,但实际上却做了】.need not have felt disappointed的意思是：“他们本来不必要感到难过,可是他们却已经感到难过了”.
又如：
1.You needn’t have hurried.你当时实在不必那么匆忙.
又因为should have done只用于谈论过去情况,主要有两个用法：
1.用于推测过去已经发生的情况.如：
He should have arrived by now.此时他本该到了.
2.用于指本该发生而实际上未发生的情况.如：
You should have told me so before.你早就应该告诉我.
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...as many of the artistes who should have appeared did not come许多艺术家本该到场的却没来.
去掉have是不可以的.