[Haskell-cafe] Re: XML transformation difficulties

[Greg Fitzgerald]

Assuming my last post was too hideous for anyone to take the time to attempt
to comprehend, let me try to simplify:
How can I extract the input of an arrow so that I can use it as a parameter
of a normal function?

How do I implement 'f' such that it can call 'g'?
f :: (ArrowXml a) => XmlTree -> a String XmlTree
g :: (ArrowXml a) => String -> a XmlTree XmlTree

Thanks,
Greg


On 7/14/06, Greg Fitzgerald <garious at gmail.com> wrote:
>
> Adding some code to go along with my last post:
>
> main = do
>    [tree]         <- runX (readDocument [(a_validate, "0")] " text.xml")
>    [fooDoc ] <- runX (constA tree >>> processChildren isFoo)
>    [expanded]     <- runX (constA tree >>> processTopDown (expandNode
> fooDoc `when` hasName "bar"))
>    [status]       <- runX (constA expanded >>> writeDocument [] "-" >>>
> getErrStatus)
>    (putStrLn . show) status
> where
>    expandNode :: (ArrowXml a) => XmlTree -> a XmlTree XmlTree
>    expandNode :: (ArrowXml a) => XmlTree -> a XmlTree XmlTree
>    expandNode foos = this    -- what here???
>    isFoo = deep (hasName "foo")
>
> The issue is that in 'expandNode', I have an XmlTree (foos) and an arrow
> whose input is the node to be replaced (also an XmlTree), but I need a
> String and an arrow whose input is the XmlTree (foos):
>
> expandNode' :: (ArrowXml a) => String -> a XmlTree XmlTree
> expandNode' name = processChildren (hasAttrValue "name" name)
>
> Somewhat related, if the output of an arrow is a string, can I get access
> to that string without using 'runX':
> getAttrValue<http://www.fh-wedel.de/%7Esi/HXmlToolbox/hdoc_arrow/Text-XML-HXT-Arrow-XmlArrow.html#v%3AgetAttrValue>:: String -> a
> XmlTree<http://www.fh-wedel.de/%7Esi/HXmlToolbox/hdoc_arrow/Text-XML-HXT-DOM-TypeDefs.html#t%3AXmlTree>String
>
> Are Arrows the wrong tool for this job?
>
> Thanks,
> Greg
>
>
>
>
>
> On 7/14/06, Greg Fitzgerald < garious at gmail.com> wrote:
> >
> > I'm trying to think of a way to translate this input, to the output
> below:
> >
> > Input:
> > <test>
> >    <foo name="a">
> >        <wahoo>A</wahoo>
> >     </foo>
> >    <foo name="b">
> >       <wahoo>B</wahoo>
> >    </foo>
> >    <foo name="c">
> >        <wahoo>C</wahoo>
> >     </foo>
> >    <group>
> >       <bar ref="b"/>
> >       <bar ref="a"/>
> >    </group>
> > </test>
> >
> > Output:
> > <test>
> >    <group>
> >        <wahoo>B</wahoo>
> >        <wahoo>A</wahoo>
> >    </group>
> > </test>
> >
> > That is, anywhere there is a 'bar', replace it with the contents of the
> 'foo' it references.  I'm having a difficult time representing this with
> HXT's Arrow API because the value of the 'ref' attribute is the output of an
> arrow, but I need it to be just a plain string so that I could use it as an
> input parameter to the 'hasAttrValue' function.  A similar problem, using
> 'processTopDown', once I traverse to a 'bar' node, I need to then traverse
> the root again to find the 'foo', but I'm in the context of the 'bar' node,
> not the root.
> >
> > My ears are open to solutions with HaXML or Scrap Your XML-plate, or
> anything else.
> >
> > Thanks,
> >
> > Greg
> >
> >
>
>
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