Reorganized environment-related functions.

lib/env.ml

@@ -0,0 +1,34 @@
+open Ast
+(* the type `environment` is defined in Ast *)
+
+
+let new_lexical env = 
+  let h = Hashtbl.create 16 in
+  h :: env
+
+let set_local env s v =
+  match env with
+  | [] -> ()
+  | e1 :: _ -> Hashtbl.replace e1 s v
+
+let rec update env s v =
+  match env with
+  | [] -> ()
+  | e1 :: erest ->
+     match Hashtbl.find_opt e1 s with
+     | None -> update erest s v
+     | Some _ -> Hashtbl.replace e1 s v
+
+let rec get_root (env : environment) =
+  match env with
+  | [] -> raise (Invalid_argument "Empty environment passed to env_root!")
+  | e :: [] -> e
+  | _ :: t -> get_root t
+
+let set_global env s v =
+  Hashtbl.replace (get_root env) s v
+
+let copy env =
+  List.map Hashtbl.copy env
+
+