How do i replace Nodes in HXT?

Question

Given a sample xml file:

<root>
  <tag attr="value">Content</tag>
  <tag attr="value2">Content</tag>
</root>

how do i replace every tag with a different tag so i get a different file:

<root>
  <tag2 attr2="value"/>
  <tag2 attr2="value2"/>
</root>

The documentation [1] seems to use Filters, is there a way to accomplish this with arrows alone?

---

Update

i am now at the point where i can replace a node like this:

runX $ readDocument [] "in.xml" 
       >>> processTopDown( 
               (eelem "tag2" += sattr "attr2" "XXX" ) 
               `when` (isElem >>> hasName "tag") ) 
       >>> writeDocument [] "test.xml"

but i have no idea on how to get the attribute right.

---

[1] http://www.haskell.org/haskellwiki/HXT#Transform_external_references_into_absolute_reference

Dicarlo

Answer 1

Try setElemName, processAttrl, and changeAttrName from Text.XML.HXT.XmlArrow:

runX $ readDocument [] "in.xml" >>> transform >>> writeDocument [] "test.xml"
  where
    transform = processTopDown $
      ( setElemName (mkName "tag2") >>>
        processAttrl (changeAttrName $ mkName . attrMap . localPart)
      ) `when` (isElem >>> hasName "tag")
    attrMap "attr" = "attr2"
    attrMap a = a

This works for me with your sample document.

Nursling

It seems that this doesn't remove the Content part of the tag. Additionally (and that's not in the question) i'd need to remove all other attributes. OTOH maybe you can point me to some decent documentation? I'm kind of lost dealing with HXT. – Dicarlo

Thanks again ... i wrote a solution based on this answer. – Dicarlo

@Florian: You can use something like changeText (const "") to clear the text content, and changeAttrl to delete the other attributes. Not sure I can point to any decent HXT tutorials, but I've found the Hackage documentation (particularly Control.Arrow.ArrowList and Text.XML.HXT.Arrow.XmlArrow) very helpful. – Nursling

i now use processChildren none which seems to remove everything below the current node. The process* functions are pretty useful :) – Dicarlo