[Haskell-cafe] ghc --make Vs runhaskell

Madhu Babu madhub.bits at gmail.com
Wed Feb 4 03:23:42 UTC 2015

Hi !,

I have the following program from “Learn You a Haskell” (
http://learnyouahaskell.com/input-and-output#randomness ). When i run this
using runhaskell, code works perfectly fine. However, when i compile and
run the binary file, code behaves differently.

Basically, in the following code, we print a line first and the read the
line from stdin. This behavior works perfectly fine when using “runhaskell
guess.hs”. But when i say “./guess”, i had to type in a number directly (
i.e. first prompt is skipped ).

btw.. i am using mac yosomite command terminal.

Any help greatly appreciated.. Thanks a lot in advance..

import System.Random
import Control.Monad(when)
main = do
  ranGen <- getStdGen
  let (rand,_) = randomR (1,10) ranGen :: (Int,StdGen)
  putStr "Guess a number between 1 and 10 : "
  numStr <- getLine
  when(not $ null numStr) $ do
    let num = read numStr
    if rand == num
      then putStrLn "Yuhaa!! you are right baby!"
      else putStrLn $ "Sorry dude!! it was " ++ show rand
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20150203/28dfa686/attachment.html>

More information about the Haskell-Cafe mailing list