How do you identify duplicate values in a numerical sequence using XPath 2.0?

Question

I have an XPath expression which provides me a sequence of values like the one below:

1 2 2 3 4 5 5 6 7

It is easy to convert this to a set of u

Answer 1

What about:

distinct-values(
  for $item in $seq
  return if (count($seq[. eq $item]) > 1)
         then $item
         else ())

This iterates through the items in the sequence, and returns the item if the number of items in the sequence that are equal to that item is greater than one. You then have to use distinct-values() to remove the duplicates from that list.