高中英语知识点：现在分词的完成式
现在分词完成式的概念：
从动作关系上看，现在分词的完成式主要表示发生在谓语动作之前的动作；从用法上看，现在分词完成式主要用作状语，表示时间或原因等。
现在分词完成式的基本用法：
1、表示时间：
如：Having noted down our names and addresses, the policeman dismissed us. 那警察把我们的姓名和地址记下之后就让我们走了。
Having found a hotel, we looked for somewhere to have dinner. 在找好旅馆之后，我们就去找吃饭的地方。
Having bought our tickets, we went into the theatre. 我们买好票后就走进剧场。
Having packed up her things, she went to book her ticket. 她收拾好行李之后就去买车票。
注：这样用的现在分词通常可以转换成时间状语从句。
如：Having finished her work, she went home. =After she had finished her work, she went home. 她干完工作就回家了。
2、表示原因：
如：Having been there once, she knew the place quite well. 由于去过那儿一次，她对那地方很熟悉。
Having invited him here to speak, we'd better go to his lecture. 我们邀请他来这儿讲演，所以我们最好去听讲。
注：这样用的现在分词通常可以转换成原因状语从句。
如：Having been there many times, he offered to be our guide. =As he had been there many times, he offered to be our guide. 他曾多次到过那里，主动提出当我们的向导。
现在分词的完成式用作状语时，通常位于主句之前，但有时也可置于主句之后，不过此时多见于表原因的场合。
如：I didn't feel terribly shocked, having expected all this. 这情况我早已料到，因此我并不感到过于震惊。
I was unable to accept your invitation. having promised to accompany my mother to the concert. 我因已答应陪我母亲赴音乐会而不能接受你的邀请。
现在分词完成式的否定式：
原则上应将not置于整个分词完成式之前。
如：Not having done it right, I tried again. 我由于没有做对，所以又试了试。
Not having finished his work, he could not leave the office. 由于工作没干完他不能离开办公室。
Not having received an answer, she decided to write him another letter. 由于没得到他的回信，她决定再给他写一封信。
现在分词完成式用于独立结构：
有时现在分词完成式可以用于独立结构。
如：The dark clouds having dispersed, the sun shone again. 乌云已散去，太阳又普照大地了。
The river having risen in the night, the crossing was impossible. 夜里河水上涨，渡河不可能了。
My turn having comeround, I was ushered into the examining room. 轮到我之后，我就被引入考场。
The last bus havingg one, we had to walk home. 最后一班公车已经走了，我们必须走路回家。
使用现在分词完成式的错点：
现在分词的完成式一般不用作定语，遇此情况可改用定语从句。
如：你知道有谁丢了一只猫吗?
误：Do you know anyone having lost a cat?
正：Do you know anyone who has lost a cat?
我想同打破窗户的人淡淡。
误：I want to talk to the person having broken the window
正：I want to talk to the person who has broken the window
注意：若将以上现在分词的完成式改为一般式也不可以，因为现在分词作后置定语时通常只表示与谓语动作同时或几乎同时发生的动作，而不能先于谓语动作而发生。
现在分词一般式与完成式的区别：
现在分词的一般式和完成式均可表示已完成或先于谓语的动作，但有区别：现在分词一般式所表示的动作虽然可以先于谓语动作，但两者之间没有时间间隔，而现在分同的完成式所表示的先于谓语的动作则与谓语动作有一定的时间间隔。
如：Locking the door, she went out. 她锁上门走了出去。
Having lost his job, he'd begun to interest himself in local voluntary work.他失业后便开始关注地方的志愿工作了。
注：有时两者意思差不多，可以换用。
如：Tying one end of the rope to his bed, he threw the other end out of the window.
Having tied one end of the rope to his bed, he threw the other end out of the window. 他把绳子的一头系在床上，另一头扔出窗外。
但是注意，用现在分词一般式代替完成式的用法通常只限于现在分词所表示的动作与谓语动词所表示的动作之间没有时间间隔的场合，比如以下情况就不可随便替换。
1、当换用会引起语义含混时。
如：看完了说明书之后，他迅速拿起了灭火器。
不妥：Reading the instructions, he snatched up the fireextinguisher.
正句：Having read the instructions, he snatched up the fireextinguisher.
前面一句用了现在分词的一般式，给人的印象好像是两个动作同时发生的，容易引起误解，故宜改用完成式。
2、当两个动作之间有一段间隔时，必须用分词的完成式。
如：Having failed twice, he didn't want to try again. 已经失败了两次，他不想再试了。
3、当第一个动作持续一段时间时，必须用分词的完成式。
如：Having been his own boss for such a long time, he found it hard to accept orders from another. 自己当老板已经这么久了，他觉得难以听从别人的差遣。
现在分词完成被动式与过去分词的区别：
现在分词的完成被动式有两个特点：一是表示完成，二是表示被动。
如：Having been bitten twice, the postman refused to deliver our letters unless we chained our dog up. 邮递员被狗咬了两次之后要我们把狗拴起来，不然就不给我们送信了。
过去分词的用法也有两个特点：一是表示完成，二是表示被动。所以有时现在分词的完成被动式与过去分词可以表示相同的意思。
如：(Having been)written in haste, the book has many mistakes. 这书因写得仓促，所以错误不少。
(Having been)born in America, he is proficient in English. 由于他是在美国出生的，所以英语很好。
有时虽然所表示的时间概念相同，但有细微区别：
如：Having been shown the lab, we left. 被领着看了实验室后，我们就离开了。
Shown the lab, we left. 被领着一看完实验室，我们就离开了。(有一种急促感)
注：以下情况通常用过去分词，而不用现在分词的完成式。
1、过去分词表示先于谓语动同发生的动作外，还可以表示与谓语动词同时(几乎同时)发生的动作，此时不可用现在分词的完成式代替。
如：He came in, followed by his secretary. 他走了进来，后面跟着他的秘书。
Convinced that they were going to poison him, he refused to eat anything. 他相信他们要毒死他，所以他拒绝进食。
2、当过去分词以表示现在或过去(当时)的状态时，也不可用现在分词的完成式代替。
如：The murderer was brought in, his hands tied behind. 凶手被带了进来，双手被绑在后面。
3、当连用具体明确的过去时间状语时，通常也只用过去分词。
如：Built in1501, the bridge is over 500 years old. 这座桥建于1501年，已有五百多年的历史。