[xquery-talk] momentary recursion dyslexia

[Philippe Michiels]

Using the string-join function, you can even write down this query as a simple 
path expression:

$book//fn:string-join(ancestor-or-self::*/name(), '/')

returns in Galax:

"book",
"book/author",
"book/author/name",
"book/author/name/last",
"book/author/name/first",
"book/author",
"book/author/name",
"book/author/name/last",
"book/author/name/first"

-Ph

On Sunday 27 November 2005 21:30, Howard Katz wrote:
> Peter Coppens has provided a solution.  I'm assuming he doesn't mind if I
> post this below.
>
> I'd already figured out nearly identical solutions using a longer XQuery to
> do the traversals, but it's nice to be reminded that a terse XPath can work
> just as well as a lengthier FLWOR. This:
>
>     concat( $p, '/'[ $p ], ... )
>
> is particularly sweet.
>
> Interestingly enough, this query works fine in Saxon but throws a type
> error ("Type of value does not match sequence type") in Galax and a
> "NOTANODE" error in Mark Logic. Boiled down, what these processors appear
> to be complaining about is this:
>
>     <a/>/fn:name(.)
>
> Can someone tell me why this is problematic for these two engines?
> Howard
>
>  > -----Original Message-----
>  > From: Peter Coppens [mailto:Peter.Coppens at datadirect.com]
>  > Sent: November 27, 2005 12:43 AM
>  > To: Howard Katz
>  > Subject: RE: [xquery-talk] momentary recursion dyslexia
>  >
>  > Here is a quick attempt. Not entirely what you want but
>  > perhaps it helps
>  >
>  > declare function local:f1($p,$i) {
>  >   concat($p,'/'[$p],fn:name($i)),
>  >   $i/*/local:f1(concat($p,'/'[$p],fn:name($i)),.)
>  > };
>  >
>  > declare function local:f2($p,$i) {
>  >   $i/*/local:f2(concat($p,'/'[$p],fn:name($i)),.),
>  >   concat($p,'/'[$p],fn:name($i))
>  > };
>  >
>  > let $book :=
>  >   <book>
>  >     <author><name><last/><first/></name></author>
>  >     <author><name><last/><first/></name></author>/
>  >   </book>
>  > return (
>  >   <f1>{local:f1("",$book)}</f1>,
>  >   <f2>{local:f2("",$book)}</f2>
>  > )
>  >
>  > Hth,
>  >
>  > Peter
>  >
>  > > -----Original Message-----
>  > > From: talk-bounces at xquery.com [mailto:talk-bounces at xquery.com] On
>  >
>  > Behalf
>  >
>  > > Of Howard Katz
>  > > Sent: Friday, November 25, 2005 11:40 PM
>  > > To: talk at xquery.com
>  > > Subject: [xquery-talk] momentary recursion dyslexia
>  > >
>  > > This seems like it should be a fairly straightforward CS101-style
>  >
>  > problem ,
>  >
>  > > but I can't seem to get it quite right. What I want is a recursive
>  > > function
>  > > that traverse an xml tree and builds xpaths. Given this variable
>  > > assignment:
>  > >
>  > >    let $book :=
>  > >       <book>
>  > >           <author><name><last/><first/></name></author>
>  > >           <author><name><last/><first/></name></author>/
>  > >       </book>
>  > >
>  > > I'd like to have the function walk the $book tree, printing as it
>  >
>  > goes:
>  > > book
>  > > book/author
>  > > book/author/name
>  > > book/author/name/last
>  > > book/author/name/first
>  > > book/author
>  > > book/author/name
>  > > book/author/name/last
>  > > book/author/name/first
>  > >
>  > > To make things even more interesting, I'd also like (possibly via a
>  > > different function, or the same one parameterized), to be able to
>  >
>  > print
>  >
>  > > out
>  > > the xpaths from the leaves up, as in:
>  > >
>  > > book/author/name/last
>  > > book/author/name/first
>  > > book/author/name
>  > > book/author
>  > > book
>  > > book/author/name/last
>  > > book/author/name/first
>  > > book/author/name
>  > > book/author
>  > > book
>  > >
>  > > I'm not sure if this reverse walker should be listing the root node
>  >
>  > twice
>  >
>  > > or
>  > > not, but that's possibly a separate issue.
>  > >
>  > > At any rate I'm having a momentary bout of recursion dyslexia. Can
>  >
>  > anyone
>  >
>  > > help?
>  > >
>  > > TIA,
>  > > Howard
>  > >
>  > > _______________________________________________
>  > > talk at xquery.com
>  > > http://xquery.com/mailman/listinfo/talk
>
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