Library Agnostic Streaming in Haskell from http://www.haskellforall.com/2014/11/how-to-build-library-agnostic-streaming.html

Main.hs

{-# LANGUAGE OverloadedStrings #-}

module Main where

import           Control.Monad.IO.Class (MonadIO, liftIO)
import           Control.Monad (MonadPlus(mzero, mplus), msum)
import           Data.Monoid (Monoid(..), (<>))
import qualified Pipes
import qualified System.IO as IO

select :: MonadPlus m => [a] -> m a
-- select  []    = mzero
-- select (x:xs) = return x `mplus` select xs

select = foldr (\x m -> return x `mplus` m) mzero

select' :: MonadPlus m => [a] -> m a
select' = msum . map return

replicateM'' :: MonadPlus m => Int -> m a -> m a
replicateM'' n = msum . replicate n

example :: (MonadIO m, MonadPlus m) => m ()
example = do
  x <- select [1, 2, 3]
  liftIO (putStrLn ("x = " ++ show x))
  y <- select [4, 5, 6]
  liftIO (putStrLn ("y = " ++ show y))

replicateM' :: MonadPlus m => Int -> m a -> m a
replicateM' n m = do
  m' <- select (replicate n m)
  m'

-- or: replicateM' n = join . select . replicate n

stdinLn :: (MonadIO m, MonadPlus m) => m String
stdinLn = do
  eof <- liftIO IO.isEOF
  if eof
    then mzero
    else liftIO getLine `mplus` stdinLn

example1 :: (MonadIO m, MonadPlus m) => m ()
example1 = do
    liftIO getLine `mplus` liftIO getLine
    liftIO (putStrLn "Foo") `mplus` liftIO (putStrLn "Foo")

example2 :: (MonadIO m, Monoid (m String), Monoid (m ())) => m ()
example2 = do
    liftIO getLine <> liftIO getLine
    liftIO (putStrLn "Foo") <> liftIO (putStrLn "Foo")

echo :: (MonadIO m, MonadPlus m) => m ()
echo = do
  str <- stdinLn
  liftIO (putStrLn str)

mapM' :: Monad m => (a -> m b) -> m a -> m b
mapM' = (=<<)

forM' :: Monad m => m a -> (a -> m b) -> m b
forM' = (>>=)

example' :: (MonadIO m, MonadPlus m) => m ()
example' = mapM' (liftIO . print) (replicateM' 10 (liftIO getLine))

main :: IO ()
main = Pipes.runListT example'

package.yaml

name: scratch
version: 0.1.0.0

dependencies:
  - base >= 4.7 && < 5
  - pipes
  - text
  - split

executables:
  scratch:
    main: Main.hs

stack.yaml

resolver: lts-8.23
packages:
- .
extra-deps: []
flags: {}
extra-package-dbs: []