HandsomeSoup: Getting basic example to work

Question

I am trying to get the basic example from http://egonschiele.github.io/HandsomeSoup/ to work:

main = do
    doc <- fromUrl "http://www.google.com/search?q=egon+schiele"
    links <- runX $ doc >>> css "h3.r a" ! "href"
    mapM_ putStrLn links

I have tried to reproduce the example like so:

module Main (main) where
import Text.HandsomeSoup
import Text.XML.HXT.Core
import Control.Monad

main = do
    doc <- fromUrl "http://www.google.com/search?q=egon+schiele"
    links <- runX $ doc >>> css "h3.r a" ! "href"
    mapM_ putStrLn links        

But, I am getting the following error:

$ runhaskell Main.hs

Main.hs:8:21:
    Couldn't match expected type `IOSLA (XIOState ()) XmlTree b0'
                with actual type `hxt-9.3.0.1:Data.Tree.NTree.TypeDefs.NTree
                                    hxt-9.3.0.1:Text.XML.HXT.DOM.TypeDefs.XNode'
    In the first argument of `(>>>)', namely `doc'
    In the second argument of `($)', namely
      `doc >>> css "h3.r a" ! "href"'
    In a stmt of a 'do' block:
      links <- runX $ doc >>> css "h3.r a" ! "href"

But I really can't seem to figure out what's going on.

Answer 1

Function fromUrl has type fromUrl :: String -> IOSArrow XmlTree (NTree XNode). So IOSArrow XmlTree (NTree XNode) is not clear IO-action.

Simplest way fix it - use let statement instead:

import Text.HandsomeSoup
import Text.XML.HXT.Core

main :: IO ()
main = do
  let doc = fromUrl "http://www.google.com/search?q=egon+schiele"
  links <- runX $ doc >>> css "h3.r a" ! "href"
  mapM_ putStrLn links