Simple State + IO

Main.hs

module Main where

import           Control.Monad.Trans.State.Lazy
import           Control.Monad.IO.Class (liftIO)

nextIntAndPrint :: StateT Int IO Int
nextIntAndPrint = do
  currentValue <- get
  let newValue = succ currentValue
  put newValue
  liftIO $ print newValue
  return newValue

intSeq :: Num s => Monad m => StateT s m a -> m s
intSeq = flip execStateT 0

main :: IO ()
main = do
  intSeq $ do
    nextIntAndPrint
    nextIntAndPrint
    nextIntAndPrint
  intSeq $ do
    nextIntAndPrint
  return ()