Hi all, The code below defines a ReadP parser which can parse either a keyword "wrapper" or an arbitrary identifier. I was hoping that it would give the output (CWrapper1,"") (CWrapper2,"") (CFunction "wrapper","") but it actually gives (CWrapper2,"") (CFunction "wrapper","") (CWrapper1,"") i.e. completed parses are returned before the parse that needs to "look" at the remaining input. I can see the logic behind the current behaviour, but in this case at least it's quite inconvenient. What do you think? Did I miss a better way to solve the problem? Should the behaviour be changed? If so, is changing it easy? import Data.Char import Control.Applicative ((<$>)) import Text.ParserCombinators.ReadP as ReadP main :: IO () main = mapM_ print test test :: [(CImportSpec, String)] test = readP_to_S parse "wrapper" where parse = do r <- choice [ token "wrapper" >> return CWrapper1, string "wrapper" >> return CWrapper2, CFunction <$> many1 (satisfy isAlpha) ] eof return r token str = do _ <- string str toks <- look case toks of c : _ | isAlpha c -> pfail _ -> return () data CImportSpec = CFunction String | CWrapper1 | CWrapper2 deriving Show Thanks Ian