Re: XSLT 2 and XSLT 3: Best Way To Get Set of Unique D

Given the variable $links that is a sequence of element()s where the elements could be from different documents, what is the best way to get the set of unique documents?

I need an XSLT 2 answer but an XSLT 3 answer would also be useful.

I feel like there's an obvious solution I'm overlooking but the only thing I can think of is to compare the document-uri() values of all the elements:

     <xsl:variable name="topicURIs" as="xs:string*"
       select="distinct-values(for $e in $links return document-uri(root($e)))"
     />
     <xsl:variable name="topics" as="document-node()*"
         select="
         for $uri in $topicURIs
         return root(($links[document-uri(root(.)) eq $uri])[1])
         "
     /> o;?

This works but seems unnecessarily complicated.

Wouldn't
  $links/root()
suffice?