A list monad transformer / a monadic list.

Monadic list example: A program which reads numbers from the user and accumulates them.

 import Control.Monad (join)
 import Control.Monad.ListT (ListT)
 import Control.Monad.Trans (lift)
 import Data.List.Class (execute, repeat, scanl, takeWhile, mapL)
 import Prelude hiding (repeat, scanl, takeWhile)
 
 main =
     execute . mapL print .
     scanl (+) 0 .
     fmap (fst . head) .
     takeWhile (not . null) .
     fmap reads $ do
       repeat ()
       lift getLine :: ListT IO String