Concurrency and interactive input

[Walker Duhon]

Hello,             I am playing around with concurrency using ghc 5.02.2.  What I’d like to do is have a bunch of threads do something indefinitely, while one thread monitors stdin for user input (the user input affects the behavior of the other threads in some way).  From the documentation I had assumed that standard Haskell I/O functions (like getline) would not block other running threads, but this doesn’t seem to be the case as illustrated here:   conTry3 = forkIO (loop 'a') >> quitYet           where             loop ch = hPutChar stdout ch >> loop ch             quitYet = do                 x <- getLine                 if x == "quit" then return ()                                else quitYet   Output: (stuff in between {} is a comment, and not part of the output) rere ttt fff dfsd fgfg fgfg aaaaaaaaaaaaaaaaaa { and on and on } dfdf dfd fdfd fgfg   fgf aaaaaaaaaaaaaaaa { and on and on } quit aaaaaaa { and on and on } {program ends}   The behavior I wanted was for ‘a’ to be printed (almost) continuously, echo the relatively infrequent input, and quit upon receiving “quit”.             I am aware (through a web search) that there was a mail thread addressing a similar issue a while back (1999) entitled:                            I thought concurrent haskell was _preemptive_!             That thread made it seem like the issue would be cleared up soon.   In any case, I would still like to be able to have an interactive input thread that doesn’t block everything in my program. Is there any way to do this?   Thanks in advance,             Walker