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

17 Feb 2006


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

Cale Gibbard