Hi Jonathan On Wed, 2008-01-09 at 21:32 -0800, Jonathan Cast wrote:
An actual coding question, abuse? We should be so lucky.
:) Your comments are much appreciated.
This function is fairly complicated, simply because of the number of separate definitions involved; I would be looking for opportunities to inline definitions here, so it's clearer what the definitions are. (Also, I would try to build a single, self-recursive function at the top level, put the call to procInfo there, and make everything else pure).
I rewrote insertInTree like below. Now it is the only function that has a StateT return type, and I also got rid of addProc, insertPid and insertParent :) insertInTree :: Pid -> StateT PsTree IO () insertInTree pid = do tree <- get if Map.member pid tree then return () else do info <- lift $ procInfo pid modify (Map.insert pid info) let ppid = parentPid info if ppid /= "0" then do insertInTree ppid modify (appendChild ppid pid) else return () I also rewrote createTree like this: createTree :: IO PsTree createTree = do entries <- getDirectoryContents "/proc" let procs = filter (=~ "^[0-9]+$") entries execStateT (mapM_ insertInTree procs) Map.empty Is that a bad way to do it? If haskell wasn't lazy this would be 3 O(n) operations, and I could write it using readDirStream to process all entries in one pass. I'm not sure if that's really necessary when laziness is present though. Thanks a lot for the other comments. I'll look into using a record for PsInfo now. Best, Andre