On Fri, Feb 5, 2010 at 10:41 AM, Andrew Coppin
Tim Attwood wrote:
Last time I tried something like this [on Windows], it didn't seem to work. I wanted to trap arrow keys and so forth, but they seem to be being used for input history. (I.e., pressing the up-arrow produces previously-entered lines of text, and none of this appears to be reaching the Haskell program itself.) Has this changed since I tried it last year?
Doesn't work in windows, at least up till 6.10.1. There's a work-around though.
{-# LANGUAGE ForeignFunctionInterface #-}
import Data.Char import Control.Monad (liftM, forever) import Foreign.C.Types
getHiddenChar = liftM (chr.fromEnum) c_getch foreign import ccall unsafe "conio.h getch" c_getch :: IO CInt
main = do forever $ do c <- getHiddenChar putStrLn $ show (fromEnum c)
Thanks for the info.
Does anyone know how this is related to the "haskeline" package on Hackage?
The haskeline package provides a readline-like library for reading in a line of input with arrow keys, tab completion, etc. It works on both Windows and unix platforms. Documentation and a full list of features can be found at http://trac.haskell.org/haskeline/ . On Windows, haskeline gets all user input by calling Win32 API functions such as ReadConsoleInputW: http://msdn.microsoft.com/en-us/library/ms684961%28VS.85%29.aspx That function returns an INPUT_RECORD struct with information about key press events (among others); those includes simple characters, arrow keys, page up/down, etc. AFAIK that's the only way to get at such events in the Windows console; there's no effective analogue to the unix setting, where e.g. pressing the up key causes stdin to receive the ANSI key sequence "\ESC[A". The source code of haskeline has examples of how to import and use those API functions: http://code.haskell.org/haskeline/System/Console/Haskeline/Backend/Win32.hsc Best, -Judah