app/Gyehoek/GenSym.hs

@@ -0,0 +1,34 @@
+{-# 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