Hi I am trying to use HXT (8.3.2) for parsing XML. I think an example will clarify what I want to do. I want to parse XML like this:
<object class="ex1">
<foo/>
<foo>
<object class="ex2"/>
<object class="ex3"/>
</foo>
<object class="ex4"/>
</object>
and want to turn it into the following Haskell data structure:
data Widget = Widget
{ cls :: String
, children :: [Widget]
}
The XML above should be turned into:
Widget "ex1" [Widget "ex2" [], Widget "ex3" [], Widget "ex4" []]
That is, I want everything but the object-tags stripped out. And I want
to keep the hierarchy of the object-tags.
I thus wrote the following program:
{-# LANGUAGE Arrows, NoMonomorphismRestriction #-}
module Main where
import Text.XML.HXT.Arrow
data Widget = Widget
{ cls :: String
, children :: [Widget]
}
deriving Show
main = (runX (readDocument [(a_validate,v_0)] "test.xrc"
>>> getObject))
>>= print
getObject =
deep (isElem >>> hasName "object") >>>
proc x -> do
cls <- getAttrValue "class" -< x
cs <- listA getObject <<< getChildren -< x -- recursive call here
returnA -< Widget cls cs
But it do not work as intended. In stead I get the following output:
[Widget {cls = "ex1", children = []},Widget {cls = "ex1", children =
[]},Widget {cls = "ex1", children = []},Widget {cls = "ex1", children =
[]},Widget {cls = "ex1", children = []},Widget {cls = "ex1", children =
[]},Widget {cls = "ex1", children = []}]
Hopefully somebody can point me in the right direction.
Greetings,
Mads Lindstrøm
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