I don't have such a nice dad as you do. as为连词

I don't have such a nice dad as yours. 

此句中有人会认为as 是介词， yours是介宾。但其实as yours= as yours is 或= as is yours. 即as分句为主系表结构，表语为such a nice dad的对应项，必须省略。系词is选择性地省略了，不省略也可以。

I don't have such a nice dad as （is）yours. 

Her articles are more interesting than I thought.

= Her articles are more interesting than I thought they would be.

Her articles are more interesting than ours. 

= Her articles are more interesting than ours are. 

所以，以上四句中as 和than都是连词。

只有as和than后接宾格代词，同时又无法还原为宾格代词为动词的宾语时，才将as和than分析为介词，此时为非正式用法，有些老学究会对这种用法嗤之以鼻。例如：

He is as tall as me.

He is taller than me.