{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE TypeFamilies #-}
module Gyehoek.GenSym where

import Numeric.Natural
import Effectful.State.Dynamic
import Effectful.Dispatch.Dynamic
import Effectful
import Language.QBE as QBE
import Data.String (IsString(fromString))
import Data.Text (Text)


class Gen a where
  gen :: Natural -> a

data GenSym :: Effect where
  GenSym :: Gen a => GenSym m a

type instance DispatchOf GenSym = Dynamic

gensym :: forall a es. (Gen a, GenSym :> es) => Eff es a
gensym = send GenSym

runGenSym :: Eff (GenSym : es) a -> Eff es a
runGenSym = reinterpret (evalStateLocal (0 :: Natural)) \_ GenSym ->
  state \n -> (gen n, succ n)
  -- state \n -> (Ident . fromString $ '.' : show n, succ n)

instance Gen (QBE.Ident s) where
  gen = Ident . fromString . ('.':) . show

instance Gen Text where
  gen = fromString . ('x':) . show