[xquery-talk] tail recursive identity transformation

[Kendall Shaw]

I don't remember seeing an xquery function that tries to return it's 
input unchanged.

Can this be improved:

declare function local:id($e as element()?, $acc as element()?) as 
element() {
   if (empty($e)) then
     $acc
  else
     local:id(()
             , element {node-name($e)} {
               $e/@*
               , for $node in $e/node()
                 return typeswitch($node)
                          case element() return local:id($node, $acc)
                          default return $node
             })
};

The idea is that functions that do more than return their input could be 
based on the function, and benefit from tail call optimization.

Kendall