Hello Everyone I am trying to learn parsec. I wrote this code to solve the problem ( http://www.spoj.com/problems/MAIN12C/ ) but getting time limit exceed so how can I improve this code ? In case of indentation, I have pasted the code at ideone ( http://ideone.com/AmxvZq ). import Data.List import qualified Text.Parsec.ByteString as PB import Text.Parsec.Prim import Text.Parsec.Char import Text.Parsec.Combinator import qualified Data.ByteString.Char8 as BS import Control.Applicative hiding ( ( <|> ) , many ) validChars :: PB.Parser Char validChars = alphaNum <|> oneOf "._" dontCare :: PB.Parser Char dontCare = oneOf "~!@#$%^&*()<>?,." {-- emailAddress :: PB.Parser String emailAddress = do _ <- many dontCare fi <- alphaNum se <- validChars th <- validChars fo <- validChars ft <- validChars restAddr <- many validChars let addr = fi : se : th : fo : ft : restAddr char '@' dom <- many1 alphaNum rest <- try ( string ".com" <|> string ".org" <|> string ".edu" ) <|> try ( string ".co.in" ) _ <- many dontCare return $ addr ++ ( '@': dom ++ rest ) --} emailAddress :: PB.Parser String emailAddress = conCatfun <$> ( many dontCare *> alphaNum ) <*> validChars <*> validChars <*> validChars <*> validChars <*> many alphaNum <*> ( char '@' *> many1 alphaNum ) <*> ( try ( string ".com" <|> string ".org" <|> string ".edu" ) <|> try ( string ".co.in" ) <* many dontCare ) where conCatfun a b c d e f dom rest = ( a : b : c : d : e : f ) ++ ( '@' : dom ++ rest ) collectEmail :: BS.ByteString -> String collectEmail email = case parse emailAddress "" email of Right addr -> addr Left err -> "" process :: ( Int , [ String ] ) -> BS.ByteString process ( k , xs ) = ( BS.pack "Case " ) `BS.append` ( BS.pack . show $ k ) `BS.append` ( BS.pack ": " ) `BS.append` ( BS.pack . show $ k ) `BS.append` ( BS.pack "\n" ) `BS.append` ( BS.pack ( unlines . filter ( not . null ) $ xs ) ) main = BS.interact $ BS.concat . map process . zip [ 1.. ] . map ( map collectEmail . BS.words ) . tail . BS.lines Regards Mukesh Tiwari