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I did some html parsing with hxt a few weeks ago and thought, that <a href="http://www.w3schools.com/xpath/xpath_syntax.asp" rel="nofollow">xpath</a> comes in quite handy. Unfortunately, I didn't come up with a perfect solution for your problem, but it might be a start for a new try. <pre><code>import Text.XML.HXT.Core import Text.XML.HXT.XPath.Arrows type XmlTreeValue a = a XmlTree String type ParsedXmlTree a = a XmlTree XmlTree type IOXmlTree = IOSArrow XmlTree XmlTree -- parses a given .html file parseHtml :: FilePath -> IOStateArrow s b XmlTree parseHtml path = readDocument [withParseHTML yes, withWarnings no] path -- "" for stdout saveHtml :: IOXmlTree saveHtml = writeDocument [withIndent yes] "" extract :: IOXmlTree extract = processChildren (process `when` isElem) -- main processing functon processHtml :: FilePath -> IO () processHtml src = runX (parseHtml src >>> extract >>> saveHtml) >> return () -- process the html structure process :: ArrowXml cat => ParsedXmlTree cat process = -- create tag <structure> for the expression given next selem "structure" -- navigate to <html><body><table><tr>... [(getXPathTrees "/html/body/table/tr") -- then combine the results >>> (getTheName <+> getWhere)] -- selects text at path <td><a...> </a></td> and creates <name>-Tag -- (// means that all <td>-tags are analysed, -- but I'm not quite sure why this is relevant here) getTheName :: ArrowXml cat => ParsedXmlTree cat getTheName = selem "name" [getXPathTrees "//td/font/a/text()"] -- selects text at path <td><a...> </a></td> -- (where the forth font-tag is taken) and creates <where>-Tag getWhere :: ArrowXml cat => ParsedXmlTree cat getWhere = selem "where" [getXPathTrees "//td/font[4]/text()"] </code></pre> The result looks like this: <pre><code>*Main> processHtml "test.html" <?xml version="1.0" encoding="UTF-8"?> <structure> <name>ABC</name> <where/> <name/> <where>Here</where> <name>EFG</name> <where/> <name/> <where>There</where> <name>HIJ</name> <where/> <name/> <where>Far away</where> </structure> </code></pre> Like I said, not quite perfect, but hopefully a start. EDIT: Maybe this looks more like your approach. Still, instead of dropping the elements you don't care about, we first choose all elements that fit and filter the results. I think it's quite fascinating that there's no generic approach for such a problem. Because, somehow, the font[4]-selection does not work with my other approach - but maybe I'm just not a good xpath user. <pre><code>processHtml :: FilePath -> IO [(String,String)] processHtml src = do names <- runX (parseHtml src >>> process1) fontTags <- runX (parseHtml src >>> process2) let wheres = filterAfterWhere fontTags let result = zip names wheres return result where filterAfterWhere [] = [] filterAfterWhere xs = case dropWhile (/= "Where:") xs of [] -> [] [x] -> [x] _:y:ys -> y : filterAfterWhere ys process1 :: ArrowXml cat => XmlTreeValue cat process1 = textNodeToText getTheName process2 :: ArrowXml cat => XmlTreeValue cat process2 = textNodeToText getWhere getTheName :: ArrowXml cat => ParsedXmlTree cat getTheName = getXPathTrees "//td/font/a/text()" getWhere :: ArrowXml cat => ParsedXmlTree cat getWhere = getXPathTrees "//td/font/text()" -- neet function to select a value within a XmlTree as String textNodeToText :: ArrowXml cat => ParsedXmlTree cat -> XmlTreeValue cat textNodeToText selector = selector `when` isElem >>> getText </code></pre> This way, you get the result you showed in your question: <pre><code>*Main> processHtml "test.html" [("ABC","Here"),("EFG","There"),("HIJ","Far away")] </code></pre> Edit2: Fun fact: it seems like the hxt-xpath library does not work quite right for such an index-selection. <a href="http://www.freeformatter.com/xpath-tester.html#ad-output" rel="nofollow">An online XPath-evaluator</a> shows the right behaviour for <code>//td/font[4]/text()</code>.
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1. COI actually did not know the XPath extensions, tks! I seemed to have no problem with using the [] predicate... even the position() one is supported. What is not supported is the "following" and "preceding" axes, which would be quite useful. I had also tried using CSS2 selectors on the Text.HandsomeSoup package for a similar effect, but they are mostly not implemented. Your second solution, while correct, is not quite what I wanted: it implies a double transversal of the HTML tree, as @shang noticed,a solution I personally prefer. I still upvoted you since your solution is more elegant than mine
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