[Haskell-beginners] Help me make sense of this error

8 Feb 2011


      Here's the three main functions involved. Let me know if I am missing
pertinent information.

I'm having difficulty unraveling this error message. Help?
...
obtainCookies :: Curl -> String -> IO ()
obtainCookies curl responseBody = do
                return $ last $ liftM $
                   mapM (flip (curlResp2 curl) resourceOpts)
                    screenScraping responseBody
...
screenScraping :: String -> [URLString]
screenScraping responseBody =
               let collectedStrings = processHTML responseBody
                   collectedIDLists = createIDList collectedStrings
                   in constructedResourceURIs urlBase collectedIDLists
...
constructedResourceURIs :: String -> [String] -> [URLString]
constructedResourceURIs url resourceIDs =
                        let frontURI = url ++ "/launchWebForward.do?"
                            midURI = map (frontURI ++) resourceIDs
                        in map (++ "&policy=0&returnTo=%2FshowWebForwards.do") midURI
HtmlParsing.lhs:81:22:
    Couldn't match expected type `[URLString]'
           against inferred type `String -> [URLString]'
    In the second argument of `mapM', namely `screenScraping'
    In the second argument of `($)', namely
        `mapM
           (flip (curlResp2 curl) resourceOpts) screenScraping responseBody'
    In the second argument of `($)', namely
        `liftM
       $ mapM
           (flip (curlResp2 curl) resourceOpts) screenScraping responseBody'

[Haskell-beginners] Help me make sense of this error

Michael Litchard