Using Megaparsec with state monad

megaparsec_state.hs

import Control.Monad.State
import Data.Void
import Text.Megaparsec          hiding (State)
import Text.Megaparsec.Char
import qualified Text.Megaparsec.Char.Lexer as L

type Parser = ParsecT Void String (State Int)

str :: String
str = "11,2,43"

main1 :: IO ()
main1 = case (runState (runParserT numbers "" str) (1::Int)) of
        (Left err, s) -> putStr (parseErrorPretty err)
        (Right xs, s) -> print $ (sum xs) + s

numbers :: Parser [Int]
numbers = do
  x <- get
  put (x+5) 
  integer `sepBy` char ','

integer = L.decimal