module Main where

import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Trans (lift)
import Data.Conduit (ConduitT, runConduit, yield, (.|))
import qualified Data.Conduit.List as CL

repIO :: (Monad m, MonadIO m) => IO () -> ConduitT () () m ()
repIO io = do
x <- liftIO io
yield x >> repIO io

repM :: Monad m => m o -> ConduitT i o m r
repM m = do
x <- lift m
yield x >> repM m

main :: IO ()
main = do
x1 <- runConduit $ repIO (getLine >>= print) .| CL.take 3
print x1 -- [(),(),()]
x2 <- runConduit $ repM (getLine >>= print) .| CL.take 3
print x2 -- [(),(),()]
let x3 = runConduit $ repM [1,2] .| CL.take 3
print x3 -- [[1,1,1],[1,1,2],[1,2,1],[1,2,2],[2,1,1],[2,1,2],[2,2,1],[2,2,2]]
let x4 = runConduit $ repM [] .| CL.take 3
print (x4 :: [[Int]]) -- []
let x5 = runConduit $ repM (Just 1) .| CL.take 3
print x5 -- Just [1,1,1]
let x6 = runConduit $ repM Nothing .| CL.take 3
print (x6 :: Maybe [Int]) -- Nothing