He is as tall as you中第一个as能否省略?

Is he as tall as I He is as tall as you中第一个as能否省略? e.g. He is a very tall boy. I think he is tall A man is never as happy as he hoped, nor as happy as he thinks Young man as he is,he knows a lot. he is not such a fool as he looks as a scientist,he is great a sucess He is not so much a writer as a reporter a child as he is/as he is a child/child as he is/child though he was哪个表达正确?原因