Re: [xml-dev] XQuery Puzzle

["Andrew Welch" <andrew.j.welch@gmail.com>]

On 17/04/2008, Fraser Goffin <goffinf@googlemail.com> wrote:
> Sorry for asking an XQuery question here, if there is a more
>  appropriate forum please let me know.
>
>  Anyway, a question relating to this simple XQuery has been circulating
>  on another group, but I am puzzled as to whether using // on a
>  sequence is valid (see the return clause below). I tried in a couple
>  of XQuery parsers (Saxon9 + the one built into XML Spy) and both
>  return no results ??
>
>  let $set := (
>     <div1>one   </div1>,
>     <div1 class="doc">two   </div1>,
>     <div1>three   </div1>,
>     <div1 class="doc">four </div1>,
>     <gotcha>START</gotcha>,
>     <div1>five   </div1>
>  )
>  return $set//gotcha/preceding-sibling::div1[@class="doc"][1]

It's because they don't share a parent that they aren't siblings - so
the preceding-sibling axis returns nothing.  Give them a common parent
such as:

let $set := <foo>
   <div1>one   </div1>,
   <div1 class="doc">two   </div1>,
   <div1>three   </div1>,
   <div1 class="doc">four </div1>,
   <gotcha>START</gotcha>,
   <div1>five   </div1></foo>

and it will return:

<div1 class="doc">four </div1>

remember to use brackets if you wanted the first in document order
rather than the nearest sibling:

($set//gotcha/preceding-sibling::div1[@class="doc"])[1]

returns

<div1 class="doc">two   </div1>


The xquery list is at x-query.com

cheers
-- 
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/