stateInNonDet.hs

#!/usr/bin/env -S cabal run -v1
{- cabal:
build-depends: base, heftia-effects ^>= 0.7
ghc-options: -Wall
-}
{-# LANGUAGE GHC2021 #-}
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}

import Control.Monad.Hefty
import Control.Monad.Hefty.NonDet
import Control.Monad.Hefty.State

testProgram :: (State String :> es, Choose :> es) => Eff es Int
testProgram = do
    () <- pure () `branch` pure ()
    s <- get
    put "modified"
    pure $ length s

main :: IO ()
main = runEff do
    _ <- runNonDet @[] do
        x <- runState "unmodified" testProgram
        liftIO $ print x
    pure ()

-- > main
-- ("modified",10)
-- ("modified",10)