[racket] sxpath, txpath and accessors

I think this is what you're looking for:

    ((sxpath '(aaa xxx (sxml:preceding '(www)))) doc)

I recommend the short tutorial near the top of this document:

    http://pkg-build.racket-lang.org/doc/sxml/sxpath.html
    
It doesn't discuss `sxml:preceding` specifically, but it shows similar
constructs.

Vincent



At Sun, 1 Mar 2015 15:42:35 -0500,
Sanjeev K Sharma wrote:
> 
> 
> I tried to send this  twice now- this is the 3rd attempt, I hope no one gets this 3 times / gets pissed.
> 
> on this page
> ~/.racket/6.1.1/pkgs/sxml/sxml/doc/sxml/sxpath.html
> 
> I read this:
> 
> "Like sxpath, but only accepts an XPath query in string form, using the standard XPath syntax.
> 
> Deprecated; use sxpath instead."
> 
> so I'd like to get the hang of sxpath but I'm somehow stuck on how to translate txpath syntax to sxpath syntax for axes and accessors
> 
> after the example document below are some of the variations I tried
> 
> #lang racket (require sxml)(require sxml/html)
> (define doc(html->xexp
> "<AAA>
>    <BBB>
>       <CCC/>
>       <www> www content <xxx/><www>
>       <zzz/>
>    </BBB>
>    <XXX>
>       <DDD>
>            <EEE/>
>            <FFF>
>               <HHH/>
>               <GGG>
>                  <JJJ>content under jjj
>                     <QQQ><lll/>content under qqq</qqq>
>                     <rrr/>
>                  </JJJ>
>                  <JJJ/>
>               </GGG>
>               <HHH/>
>            </FFF>
>       </DDD>
>    </XXX>
>    <CCC>content in ccc
>       <DDD/>
>    </CCC>
> </AAA>"))
> 
> 
> ((txpath"/aaa/xxx/preceding::*")doc);expect;'((zzz) ... (www "\n" "      " (zzz) "\n" "   "))))
> 
> ((txpath"/aaa/xxx/preceding::zzz")doc);expect '((zzz))
> ((txpath"/aaa/xxx/preceding::www")doc);expect '((www "\n" " ...   " (zzz) "\n" "   ")))
> ((txpath"/aaa/xxx/preceding::www/following::lll")doc);expect '((lll) (lll))
> 
> ;from the doc,
> ;lists in the s-expression syntax correspond to string concatenation in the txpath syntax.
> ;((sxpath'(aaa xxx ddd fff ggg jjj qqq))doc);expect '((qqq (lll) "content under qqq"))
> 
> ((sxpath'(aaa xxx preceding))doc)
> 
> ((sxpath'(aaa xxx preceding::www))doc)
> ((sxpath'(aaa xxx preceding::zzz))doc)
> ((sxpath'(aaa xxx preceding::bbb))doc)
> 
> ((sxpath'(aaa xxx "preceding"))doc)
> ((sxpath'(aaa xxx "preceding::zzz"))doc);
> ((sxpath'(aaa xxx "preceding::www"))doc);
> 
> ((sxpath'(aaa xxx "preceding::*"))doc)
> ;((sxpath "/aaa/xxx/preceding::*")doc); works
> ((sxpath'(aaa xxx preceding::*))doc)
> ((sxpath'(aaa (xxx (preceding::*))))doc)
> ((sxpath'(aaa (xxx (preceding::*))))doc)
> ((sxpath'(aaa (xxx (preceding::"*"))))doc)
> ((sxpath'(aaa (xxx "preceding::*")))doc)
> ((sxpath'(aaa (xxx ("preceding::*"))))doc)
> 
> ((sxpath'(aaa xxx preceding::*))doc)
> ((sxpath'(aaa xxx preceding::*))doc)
> ((sxpath'(aaa xxx "preceding::*"))doc)
> ((sxpath'(aaa xxx ,"preceding::*"))doc)
> ((sxpath'(// aaa /xxx /"preceding::*"))doc)
> 
> ;((sxpath'(//aaa /xxx/preceding"::*"))doc); error
> ;(sxml:preceding::*(sxpath'(aaa xxx))doc); error
> 
> ((sxml:preceding 'eq) doc) ;#<procedure:...l/sxpath-ext.rkt:578:4>
> ((sxml:preceding(sxpath'(aaa xxx)))doc);#<procedure:...l/sxpath-ext.rkt:578:4>
> 
> 
> 
> 
> I'd like to get the other axes and accessors working but now that I've spent some time on this I also REALLY want to know what my blind spot is here.  Hope I didn't miss something glaringly obvious.
> 
> ____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users