windows - Haskell: read input character from console immediately, not after newline

Question

I've tried this:

main = do
    hSetBuffering stdin NoBuffering 
    c <- getChar

but it waits until the enter is pressed, which is not what I want. I want to read the character immediately after user presses it.

I am using ghc v6.12.1 on Windows 7.

EDIT: workaround for me was moving from GHC to WinHugs, which supports this correctly.

Answer 1

Yes, it's a bug. Here's a workaround to save folks clicking and scrolling:

{-# LANGUAGE ForeignFunctionInterface #-}
import Data.Char
import Foreign.C.Types
getHiddenChar = fmap (chr.fromEnum) c_getch
foreign import ccall unsafe "conio.h getch"
  c_getch :: IO CInt

So you can replace calls to getChar with calls to getHiddenChar.

Note this is a workaround just for ghc/ghci on Windows. For example, winhugs doesn't have the bug and this code doesn't work in winhugs.