I think you need to put liftIO in front of the IO actions you want to do inside the CGI Monad. Like in this example

http://www.haskell.org/haskellwiki/ Practical_web_programming_in_Haskell#File_uploads

(Why did I need to use google to find that? The wiki search in awful. Searching for CGI returns nothing, whereas with google the above is the first hit.) Am 13.06.2008 um 15:41 schrieb Cetin Sert:

Hi,

Could someone please care to explain what I am doing wrong below in cgiMain2 and how can I fix it?

./Main.hs:25:15: No instance for (MonadCGI IO) arising from a use of `output' at ./Main.hs:25:15-20 Possible fix: add an instance declaration for (MonadCGI IO) In the first argument of `($)', namely `output' In the expression: output $ renderHtml $ page "import" fileForm In the definition of `upload': upload = output $ renderHtml $ page "import" fileForm

./Main.hs:57:29: Couldn't match expected type `CGI CGIResult' against inferred type `IO CGIResult' In the first argument of `handleErrors', namely `cgiMain2' In the second argument of `($)', namely `handleErrors cgiMain2' In the expression: runCGI $ handleErrors cgiMain2

import IO import Network.CGI import Text.XHtml

import qualified Data.ByteString.Lazy as BS

import Control.Monad (liftM) import Data.Maybe (fromJust)

import Interact

fileForm = form ! [method "post", enctype "multipart/form-data"] << [afile "file", submit "" "Upload"]

page t b = header << thetitle << t +++ body << b

cgiMain1 = do getInputFPS "file" ↠ λms → maybe upload contents ms ↠ return where upload = output $ renderHtml $ page "import" fileForm contents = outputFPS

cgiMain2 = do getInputFPS "file" ↠ λms → maybe upload contents ms ↠ return where upload = output $ renderHtml $ page "import" fileForm contents = λs → do (i,o,h,_) ← runUnzip BS.hPutStr i s c ← BS.hGetContents o outputFPS c

{- (i,o,h,_) ← runUnzip BS.hPutStr i s BS.hGetContents o ↠ outputFPS -}

{- liftM :: (Monad m) => (a1 -> r) -> m a1 -> m r liftIO :: (MonadIO m) => IO a -> m a

saveFile n = do cont <- liftM fromJust $ getInputFPS "file" let f = uploadDir ++ "/" ++ basename n liftIO $ BS.writeFile f cont return $ paragraph << ("Saved as " +++ anchor ! [href f] << f +++ ".") -}

runUnzip = runInteractiveCommand "unzip -l /dev/stdin"

main = runCGI $ handleErrors cgiMain2

Best Regards, Cetin Sert

P/s: what are lifts o_O? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe