Reorganized basically everything, making way for the compiler

interpreter/env.ml

@@ -0,0 +1,38 @@
+open Ast
+(* the type `environment` is defined in Ast *)
+
+let default_env: environment = [Hashtbl.create 1024];;
+
+let copy (env : environment) : environment =
+  List.map Hashtbl.copy env
+
+let make_env () = copy default_env
+
+let new_lexical (env : environment) : environment = 
+  let h = Hashtbl.create 16 in
+  h :: env
+
+let set_local (env : environment) (s : string) (v : lisp_val) : unit =
+  match env with
+  | [] -> ()
+  | e1 :: _ -> Hashtbl.replace e1 s v
+
+let rec update (env : environment) 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 : environment) s v =
+  Hashtbl.replace (get_root env) s v
+
+let set_default s v =
+  set_global default_env s v