On 03/01/2025 10:52, Roger L Costello costello@xxxxxxxxx wrote
> $fieldnames is a list of strings, e.g.,
>
> ('TYPE', 'USAGE_CD', 'DIR', 'WGS_LAT', 'TYPE', 'WGS_LONG', 'TURN_DIR', 'DIR', 'TYPE')
>
> I want a list of the duplicates in $fieldnames:
>
> ('TYPE', 'DIR')      <-- I don't want any duplicates in this list
>
> Is there a simple XPath expression to obtain the list of duplicates in $fieldnames?

What about a simple filter? Not complex, but might be O(n^2) in worst case

filter(distinct-values($fieldnames),function($s){count($fieldnames[. = $s]) gt 1})

-- 
*John Lumley* MA PhD CEng FIEE
john@xxxxxxxxxxxx