[Haskell] Simple question about IO in hugs and ghc

Sun, 26 Sep 2004 04:42:01 -0700

Hi,
 
When I run my main function I get an error:
 
The prompt does not wait for user input and thus my parser fails with an empty head.
 
Is there a switch to not echo to the console?  Is this the problem?  It happens in both Hugs and GHC
 
main :: IO ()
main = do
       putStr "sentence? "
       input <- getLine
       case input of
            "quit" -> putStr "bye.\n"
            _      -> do
                           let res = get_result $ proof $ do_proof $ getInput input
                                in if res == Nothing
                                   then putStr ("-> Nothing\n")
                                   else putStr ("-> " ++ (show $ unJust res) ++ "\n")
                                   main
----
 
Sample output:
START>
$ mmccg.exe
 
sentence?
Fail:  Prelude.head: empty list
<END
 
 
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