[Haskell-beginners] remove XML tags using Text.Regex.Posix

[aditya siram]

This is how I did it using the HXT library :

Prelude Text.XML.HXT.Parser.XmlParsec Text.XML.HXT.Arrow.XmlIOStateArrow
Text.XML.HXT.Arrow> runX (readString [] "<tag>123</tag>" >>> getXPathTrees
"tag" >>> getChildren >>> getText)
["123"]

Everything after "Prelude" upto the first ">" is what you have to import to
make this work.
-"readString" converts the input string into a internal representation of an
XML tree
-"getXPathTrees" sets the path to all <tag>'s,
-"getChildren" narrows it down to the data between <tag> and </tag>,
-"getText" extracts all the data between those tags,
-"runX" fires up the whole process and returns the results as a list in the
IO Monad.

hth,
deech

On Tue, Sep 29, 2009 at 2:25 PM, Robert Ziemba <rziemba at gmail.com> wrote:

> I have been working with the regular expression package (Text.Regex.Posix).
>  My hope was to find a simple way to remove a pair of XML tags from a short
> string.
>
> I have something like this "<tag>Data</tag>" and would like to extract
> 'Data'.  There is only one tag pair, no nesting, and I know exactly what the
> tag is.
>
> My first attempt was this:
>
>   "<tag>123</tag>" =~ "[^<tag>].+[^</tag>]"::String
>
> result:  "123"
>
> Upon further experimenting I realized that it only works with more than 2
> digits in 'Data'.  I occured to me that my thinking on how this regular
> expression works was not correct - but I don't understand why it works at
> all for 3 or more digits.
>
> Can anyone help me understand this result and perhaps suggest another
> strategy?  Thank you.
>
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