[Haskell-cafe] cgi liftM liftIO

2008-06-13 Thread 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?
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Re: [Haskell-cafe] cgi liftM liftIO

2008-06-13 Thread Adrian Neumann 
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?
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Re: [Haskell-cafe] cgi liftM liftIO

2008-06-13 Thread Gwern Branwen 
On 2008.06.14 08:05:48 +0200, Adrian Neumann <[EMAIL PROTECTED]> scribbled 4.0K 
characters:
> 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.)

IIRC, MediaWiki search will not search for anything shorter than 4 characters 
(as an optimization, I think). This is admittedly annoying when you are 
searching not for 'the' but 'IRC' or 'CGI'...

--
gwern
William Gap subversives Lexis-Nexis SADMS Blowpipe GRU Posse ISCS mailbomb


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