Hello,

Is it possible to get XSLT to transform XML that looks like this:
<foo>
    <bar leftparen="((" rightparen="" num="3" oper="*" />
    <bar leftparen="" rightparen=")" num="2" oper="-" />
    <bar leftparen="" rightparen=")" num="2" />
</foo>

into something that looks like this:
<foo>
   <paren>
     <paren>
       <bar num="3" oper="*"/>
       <bar num="2" oper="-"/>
     </paren>
     <bar num="2"/>
   </paren>
</foo>

"paren" elements are opened and closed based on the number of '(' in each element's leftparen and rightparen attributes.
Can anyone help?
Thanks,

Rob

It's certainly possible, but it's not easy, and I'm not going to write the code for you...

You might like to tackle an easier problem first: start with

<open-paren level="0"/>
<open-paren level="1"/>
<bar num="3" oper="*"/>
<bar num="2" oper="-"/>
<close-paren level="1">
<bar num="2"/>
<close-paren level="0">

You can tackle that with a recursive approach along the lines:

process-sequence($S):

* take the first element in S
* if it's not an open-paren, copy it, and apply the same rules to the sequence $S[position() != 1]
* if it is an open-paren, output a <paren> element, whose content is generated by calling process-sequence applied to all the elements up to (and excluding) the matching close-paren.

Once you've got that working, think about how to convert the input from the form you gave into the form above - I suspect that part is relatively easy.


Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

I knew it would require recursion and have tried that...however I must be doing something wrong as I can't get it to work, the C# transform doesn't appear to like the fact that I haven't closed the tag yet!
Also, I'm not sure what you mean by:

process-sequence($S):

Is that some sort of built in function? I can't find any reference to that anywhere.

No, process-sequence was just a name I invented for the algorithm so I could refer to it again. It might turn into a named template or XSLT 2.0 function in your actual code.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference