your pattern match of (s:sx) seems to be the cause of the delay try --Process the input mProcess :: String -> State String mProcess sx = do b <- isOn if ( head sx == 't' ) then toggle else return () appOut (tuUpper b (head sx)) (mProcess (tail sx)) instead -----Original Message----- From: Tom Bevan [mailto:tom@regex.com.au] Sent: 14 January 2002 05:58 To: Haskell Cafe List Subject: Help using a state monad Hi all, I'm trying to get a feel for how monads might be used in a Haskell program and develop an approach that would be useful for larger projects. I have tried to model in miniture a programme which takes input from 'standard in' and processes it against an internal state and then returns the processed result to 'standard out'. My problem is that, becuase of the way I have constructed the programme 'standard out' lags behind by one character. I'm hoping that someone might have a better design they could share with me. Tom.