Reorganized basically everything, making way for the compiler

interpreter/eval.ml

@@ -0,0 +1,76 @@
+open Ast;;
+
+
+(* the type annotations are unnecessary, but help constrain us from a
+potentially more general function here *)
+let rec eval_sym (env: environment) (s: string) =
+  match env with
+  | [] -> raise (Invalid_argument (Printf.sprintf "eval_sym: symbol %s has no value in current scope" s))
+  | e :: rest ->
+    match Hashtbl.find_opt e s with
+    | None -> eval_sym rest s
+    | Some v -> v
+
+let rec eval_one env = function
+  | LSymbol s -> eval_sym env s
+  | LCons (func, args) -> eval_call env (eval_one env func) args
+  | LQuoted v -> v
+  | v -> v (* All other forms are self-evaluating *)
+
+(* Evaluate a list of values, without evaluating the resulting
+function or macro call. Since macros and functions inherently
+look similar, they share a lot of code, which is extracted here *)
+and eval_list env l =
+  match l with
+  | LNil -> LNil
+  | LCons (a, b) -> LCons (eval_one env a, eval_list env b)
+  | _ -> raise (Invalid_argument "eval_list: cannot process non-list")
+
+and eval_body env body =
+  match body with
+  | LNil -> LNil
+  | LCons (form, LNil) -> eval_one env form
+  | LCons (form, next) -> ignore (eval_one env form); eval_body env next
+  | _ -> LNil
+
+and bind_args env = function
+  | (LNil, LNil) -> ()
+  | (LSymbol s, v) -> Env.set_local env s v
+  | (LCons (LSymbol hl, tl), LCons (ha, ta)) -> Env.set_local env hl ha; bind_args env (tl, ta)
+  | _ -> invalid_arg "cannot bind argument list for function"
+
+and eval_apply args = function
+  | LLambda (e, l, b)
+  | LFunction (_, e, l, b) ->
+    let lexical_env = Env.new_lexical e in
+    bind_args lexical_env (l, args);
+    eval_body lexical_env b
+  | LUnnamedMacro (e, l, b)
+  | LMacro (_, e, l, b) ->
+    let lexical_env = Env.new_lexical e in
+    bind_args lexical_env (l, args);
+    eval_body lexical_env b
+  | v ->
+    invalid_arg ("Non-macro non-function value passed to eval_apply "
+        ^ dbg_print_one v)
+
+and eval_call env func args =
+  match func with
+  | LBuiltinSpecial (_, f) -> f env args
+  | LBuiltinFunction (_, f) -> f env (eval_list env args)
+  (* The function calls don't happen in the calling environment,
+     so it makes no sense to pass env to a call. *)
+  | LLambda _
+  | LFunction _ -> eval_apply (eval_list env args) func
+  (* Macros are the same, they just return code that *will* be evaluated
+  in the calling environment *)
+  | LUnnamedMacro _
+  | LMacro _ -> eval_one env (eval_apply args func)
+  | v -> raise (Invalid_argument 
+                  (Printf.sprintf "eval_apply: cannot call non-function object %s" (dbg_print_one v)))
+
+let eval_all env vs =
+  let ev v = eval_one env v in
+  List.map ev vs;;
+
+