Heisastallaboyashisbrother.这句中的astallaboyas不理解

as tall a boy as麻烦给解释一下这个结构是什么，不是很好理解，谢谢！

He is as tall a boy as his brother.这句中的as tall a boy as不理解
句子意思：他是一个像他哥哥/弟弟一样高的男孩

第一个AS 相当于副词SO 的功能；第二个SO 是介词功能

等于下面句子

He is so tall a boy as his brother (so +adj + noun )

He is a boy who is as tall as his brother

so + adj.such + a(n) + n.

so + adj. + a(n) + n.such+ n. (pl.)

so + adj. + n. (pl.)such +n. (pl.)

so + adj. + n. [不可数]such+n. [不可数]

so foolish such a fool

so nice a flower such a nice flower

so many/ few flowers such nice flowers

so much/little money.such rapid progress

so many peoplesuch a lot of people

so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。

so…that与such…that之间的转换既为 so与such之间的转换。

用which。 which boy is your brother? 如果对the tall boy提问，则用who.

He is a boy as tall as his brother. 他是个像他兄弟那么高的男孩. 为了强调高这个属性, 把as tall提前了.

He is as tall a boy as his brother（插入式)= He is a boy as tall as his brother.(普通式) 这里前后两个as tall as 都是一样的，as tall as his brother 作为状语前者是前置（非前置在句首而插入在句中），后者为状语后置 前者翻译：他是和他兄弟一样的高个子男孩。 后者翻译：他是一个和他兄弟一样高的男孩。