Here's your program, but a little slimmer. I think size counts for something in the shootout. Still runs at the same speed though :-( The program seems to spend about 50% reading the files, 22% building the hash table (7% chopping input into lines, 11% inserting into table), 25% spellchecking (11% chopping input into lines, 12% hash lookup). So until String IO gets a bit faster, you're stuck. You could look into using Peter Simons' BlockIO, and operating over bytes rather than chars. But then you'd have to include that in the submitted code, because it's not part of the standard libraries. ---------------------------------------------------- module Main where import Data.HashTable import System.IO buildHash input = do table <- new (==) hashString sequence_ [ insert table w True | w <- lines input ] return table check :: HashTable String Bool -> String -> IO () check table w = do r <- Data.HashTable.lookup table w maybe (putStrLn w) (const $ return ()) r spellcheck table input = sequence_ [ check table w | w <- lines input ] main = do table <- (readFile "Usr.Dict.Words" >>= buildHash) hGetContents stdin >>= spellcheck table ----------------------------------------- ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************