Having finished the homework,he went to bed.Having finished

Having finished ——现在分词的完成形式.
他做完作业后,就去睡觉了.
Having finished the homework,he went to bed.（完成作业在先,去睡觉在后.中间有停顿.）
分词的时态及其判断
* 过去分词没有时态形式的变化,因此 been done 和 had done 任何时候都不会出现.
* 现在分词有两种时态形式：
一般形式：doing
完成形式：having done
* 判断分词用什么形式主要是要与句子中的主要动词行为发生时间进行对比,如果同时或相继发生,用一般式；如果分词的行为的发生时间早于主要动词的发生时间,则用完成式.例如：
--Working there,we learned a lot from them.(劳动的同时学到了许多)
--Looking out of the window,I saw groups of children play games.(先望出去,接着就看到,视线没有断开)
-- Having finished his work,he went to help his classmates.(完成工作在前,帮助他人在后,中间有停顿)
-- Not having done it right,I tried again.(没做好在前,明显停顿后再次尝试)
* 伴随状语是与主要动词的行为同时发生的动作,如果有前有后就不成其为伴随,所引不能用完成形式 having done 表示,否则就是逻辑错误.