sample StateT

statetExample.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Example () where

import Control.Monad
import Control.Monad.IO.Class
import Control.Monad.State.Strict


type MyAppState = Int -- Your state implementation here.

newtype MyApp a = MyApp { runMyApp ::  StateT MyAppState IO a }
    deriving (Functor, Applicative, Monad, MonadState MyAppState, MonadIO)
    

initAppState :: MyAppState
initAppState = 0 -- dummy placeholder for empty state, needs implementation

goApp :: MyApp n -> IO n
goApp init' = evalStateT (runMyApp init') initAppState


doStateStuff :: MyApp ()
doStateStuff = do
    liftIO . putStrLn $ "Hit Some button to increment your state counter"
    _ <- liftIO getChar
    modify (+1)
    n <- get
    liftIO . putStrLn $ "Your State counter is: "++(show n)
    doStateStuff

main :: IO ()
main = goApp doStateStuff