Re: [Haskell-cafe] Re: Unexpected results with simple IO

What version of GHC are you using? Your code works for me in rxvt in Cygwin, with GHC 6.4.1. But I remember having that same problem earlier (in some earlier GHC version, so it may be fixed by now). The solution was to run hFlush after each putStr, like so: import System.IO (hFlush, stdout) do putStr "..." hHlush stdout ... If I remember correctly, the problem only occurred in GHCi and Hugs -- not when compiling the code. / Emil Maurício skrev:

You're right... I was running the example in rxvt, in cygwin. Now I tried in Windows command shell and it works.

Thanks, Maurício

Cale Gibbard wrote:

...

That doesn't happen for me at all, it works just fine. Maybe it's something wrong with your terminal? You could possibly try playing with the buffering settings on stdout, using hSetBuffering in System.IO.

- Cale

On 17/02/06, Maurício wrote:

...

Dear Haskell users,

I have a problem using IO. The small test program below asks the user to guess from a list of random numbers between 1 and 10. Everything works well excepts for one problem: all the messages ("Guess a number...", "Right..." and "Wrong...") are printed after the program finishes, i.e., I have to use it blind. I'm afraid I misunderstand something important about lazyness or monads... What am I doing wrong?

Thanks, Maurício

module Main where import Random

main = do r_gen <- getStdGen --random generator let r_list = (randomRs (1,10) r_gen) --random list guess_loop (r_list)

guess_loop (r:r_others) = do putStrLn "Guess a number between 1 and 10:" n <- readLn if n==r then do putStrLn "Right! :)" return () else do putStrLn "Wrong... :(" guess_loop r_others

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