[plt-scheme] Re: getting data out of xexpr's (xml)

From: Dave Gurnell (d.j.gurnell at gmail.com)
Date: Tue Jan 8 09:22:48 EST 2008

My two cents on XML matching:

I tend to find match and plt-match to be a little restrictive for XML  
pattern matching. The classic example of this is attributes on  
elements, which can arrive in any order. For example:

     '(a (@ [href "http://www.example.com"]
            [target "_new"])
         "Example web site")

is equivalent to:

     '(a (@ [target "_new"]
            [href "http://www.example.com"])
         "Example web site")

but you have to match against it with two clauses like this:

     (match link
       [`(a (@ [target ,target] [href ,href]) ,text)
       [`(a (@ [href ,href] [target ,target]) ,text)

or using nested matches, one for the elements and one for the  

Perhaps there's an order-independent list pattern in plt-match that I  
don't know about? If not, the XML matching library is probably better  
for this kind of thing. However, xml-match it has its own limitations  
too (I can't remember these off the top of my head: I just remember  
that writing delicious.plt wasn't as straightforward as I might have  

I haven't tried SXPath yet.


-- Dave
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