[Haskell-beginners] error handling approaches

11 Sep 2011

      Here's the gist of the code I am looking to incorporate error handling into
...
worldHandler :: ProcessState -> JobCount -> IO ()
worldHandler world jCount = do
   putStrLn "Entered worldHandler"
   jcount <- takeMVar jCount
   if jcount > 0
      then incrementThenDone jcount
      else doJobProcessing jcount
      where incrementThenDone jcount = do
                putMVar jCount (jcount+1)
...
doJobProcessing jcount = do
                putMVar jCount (jcount+1)
                preProcess world
                initiateJob world
                makeChart world
Here's main
...
main :: IO ()
main = do
    world <- (newEmptyMVar :: IO ProcessState)
    jCount <- (newMVar 0 :: IO JobCount)
    installHandler userDefinedSignal1 (Catch $ worldHandler world jCount) Nothing
    forever (threadDelay 10000)
the functions preProcess, initiateJob, and makeChart is where I need
be concerned with errors. The idea is that if any of those functions
fail, I decrement jCount. call logError, and continue waiting for the
next signal.
each of these functions will be starting another process,
readProcessWithExitCode looks like what I want. I will then use the
exit code to determine success or failure.

General ideas about how to approach this, and any questions that come
to mind would be appreciated.

[Haskell-beginners] error handling approaches

Michael Litchard