Anwendung von Arrows in HXT

http://www.fh-wedel.de/~si/HXmlToolbox/http://www.haskell.org/haskellwiki/HXT/Eingabe:

<problem type="termination">
<trs> <rules> <rule> <lhs> 
   <funapp> <name>a</name> <arg> ...

Programm:

import Text.XML.HXT.Arrow
getProblem = atTag "problem" >>> proc x -> do
    ty <- getType <<< getAttrValue "type" -< x
    rs <- getTRS <<< getChild "trs" -< x
    ...
    returnA -< case st of ...