IoKnot?

IoKnot.hs

module IoKnot where

import System.IO

-- this is how you could make your version *working* (well not really, the mapM is really strange)
f :: [String] -> IO [String]
f = mapM $ \x -> putStr x >> putStr ": " >> hFlush stdout >> getLine

g :: [String] -> IO ()
g x = do
  x' <- f ("start":x)
  g x'

-- but this is what I think you really want to do
dialog :: String -> IO ()
dialog prompt = do
  putStr prompt
  putStr ": "
  hFlush stdout
  next <- getLine
  dialog next

main :: IO ()
main = do
  -- yours: g []
  -- what I think:
  dialog "start"