[xquery-talk] Help understanding typeswitch-based Identity Transform

[Bridger Dyson-Smith]

Hi list --

I'm trying to get a better understanding of identity transforms in Xquery
and I don't understand the finer points of the approaches for dealing with
specific elements.

I've finally to become used to the XSLT approach, using a matching template
to process `field[@name='first']`, e.g. would someone be willing to shine
some light on different methods for dealing with this?

Thanks very much for your time and trouble.
Best,
Bridger

Example:

declare variable $input :=
  <docs>
    <doc>
      <title>ABC: The Alphabet</title>
      <author>Some Person</author>
      <fields>
        <field name="first">First Field</field>
        <field name="second">Second Field</field>
      </fields>
    </doc>
  </docs>;

declare function local:passthru( $node as node()* ){
  local:dispatch($node/node())
};

declare function local:dispatch(
  $nodes as node()*
) as item()* {
  for $node in $nodes
  return
    typeswitch($node)
      case text() return $node
      case element(docs) return local:passthru($node)
      case element(doc) return local:docf($node)
      case element(title) return local:title($node)
      case element(author) return local:author($node)
      case element(fields) return local:passthru($node)
      case element(field) return () (:return empty sequence:)
      default return local:passthru($node)
};

declare function local:docf($node) {
  <new>{local:dispatch($node/node())}</new>
};

declare function local:title($node) {
  <new-title>{local:dispatch($node/node())}</new-title>
};

declare function local:author($node) {
  <new-author>{local:dispatch($node/node())}</new-author>
};

local:dispatch($input)

Output should look something like:

<new>
  <new-title>ABC: The Alphabet</new-title>
  <new-author>Some Person</new-author>
  <new-subject>First Field</new-subject>
  <new-section>
    <new-entry>Second Field</new-entry>
  </new-section>
</new>
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