to have done  不定式 + 现在完成式 总结分享
前一段时间对上述结构不是理解，查了CD的讨论也没有特别满意的解释，经咨询老师后恍然大悟，现整理如下共大家参考。
第一个用法，也就是在GMAT中常出现的  -  用在indirect speech （report speech）- 也就是说信息提供的人不是直接的陈述者 
如human beings are thought to have first entered the Americans  大全325题
human beings first entered这个观点不是这篇文章的作者这么想，而是 are thought（被认为 – 被人们认为）
 
因为to have 是用在indirect speech，所以经常跟在think, claim, believe 等于陈述信息相关的单词后面多以被动的形式出现. To 前面动词的事态没有限制
 
可以从以下的例子中仔细体会 – 例子是从CD 的贴子中借的，都是大全例的例子
 
    it is thought to have happened 
 
    six teenagers    claimed to have had vision of the virgin
 
    it is believed to have been the largest 
 
    few people are known to have recovered
 
    thought by some scholars to have occurred
 
    alleged to have been worn 
 
 
经典的例子是大全157题，同时包括 to have 和 to be 
 
Balzac drank more than fifty cups of coffee a day and died of caffeine poisoning; furthermore, caffeine did not seem to bother Samuel Johnson, the great writer and lexicographer, who was reported to have drunk twenty-five cups of tea at one sitting.
(A) furthermore, caffeine did not seem to bother
(B) however, caffeine did not seem to bother
(C) however, caffeine did not seem to have bothered
(D) furthermore, caffeine did not seem to have bothered（B）
(E) in addition, caffeine did not seem to bother
做这个题的时候有些朋友可能看到没有划线部分的have drunk 后根据平行原则选C， 但这里因为seem 不是表达别人意见的词，而是做着对这件事情的看法，所以就没有必要用to have bothered 正确 答案是B. 如果我们把句子改称
however, it is said caffeine did not to have bothered 这样就可以了
 
而没有划线部分who was reported to have drunk twenty-five cups of tea at one sitting注意一下这里的was reported 也就是 drunk twenty-five cups of tea at one sitting 这个表述不是作者直接的而是引用别人的report 的 所以用了to have 这个形式
 
第二种用法是future 
 
he is to have become the next president by the end of January 
 
- he will have become the next  与这个意思想象，不过 will 是uncertain    is to have  是certain 
 
he was to have been next president (在过去的时点上看未来) 
 
 
还有现在完成式和过去完成式的用法简单地补充一下
 
大家都知道现在完成式是跟time 有关，time 对是用现在完成式还是用一般过去式的一个基准。如果有明确的时间或标志词例如，since 等比较好判断，但句子里没有明显的提示时应该怎么判断呢？另外的一半的判断基准是作者是否对他所表达的东西的态度 – 是一般的陈述还是强调。 如果是一般的陈述那就用一般过去时，如果作者对描述的东西的态度是强调那就用现在完成式 FOR EXAMPLE
 
I didn’t eat lunch. I am not hungry  只是一般的陈述 
 
I haven’t eaten lunch, so I am hungry 这里的前面的部分时后面句子的原因，为了表达后面的这个结果必须强调没有吃午饭的这件事情。
 
 
GMAT的现在完成式大多符合这个规律
 
如果那位朋友