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POHXT: Select a node by position with HXT in Haskell?
 

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    <p>I’m trying to parse some XML files with Haskell. For this job I’m using <a href="http://www.haskell.org/haskellwiki/HXT" rel="nofollow">HXT</a> to get some knowledge about arrows in real world applications. So I’m quite new to the arrow topics.</p> <p>In XPath (and <a href="http://hackage.haskell.org/packages/archive/HaXml/1.24/doc/html/Text-XML-HaXml-Combinators.html#v%3aposition" rel="nofollow">HaXml</a>) it’s possible to select a node by position, let’s say: <code>/root/a[2]/b</code></p> <p>I can’t figure out how to do something like that with HXT, even after reading the documentation again and again.</p> <p>Here is some sample code I’m working with:</p> <pre><code>module Main where import Text.XML.HXT.Core testXml :: String testXml = unlines [ "&lt;?xml version=\"1.0\"?&gt;" , "&lt;root&gt;" , " &lt;a&gt;" , " &lt;b&gt;first element&lt;/b&gt;" , " &lt;b&gt;second element&lt;/b&gt;" , " &lt;/a&gt;" , " &lt;a&gt;" , " &lt;b&gt;third element&lt;/b&gt;" , " &lt;/a&gt;" , " &lt;a&gt;" , " &lt;b&gt;fourth element&lt;/b&gt;" , " &lt;b&gt;enough...&lt;/b&gt;" , " &lt;/a&gt;" , "&lt;/root&gt;" ] selector :: ArrowXml a =&gt; a XmlTree String selector = getChildren /&gt; isElem &gt;&gt;&gt; hasName "a" -- how to select second &lt;a&gt;? /&gt; isElem &gt;&gt;&gt; hasName "b" /&gt; getText main :: IO () main = do let doc = readString [] testXml nodes &lt;- runX $ doc &gt;&gt;&gt; selector mapM_ putStrLn nodes </code></pre> <p>The desired output would be:</p> <pre><code>third element </code></pre> <p>Thanks in advance!</p>
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