tcl: Phase 4 env-as-value — current-env/eval-in-env/env-lookup/env-extend (+5 tests, 342/342 total)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hosts/ocaml/lib/sx_primitives.ml

@@ -2010,4 +2010,36 @@ let () =
         end
       done;
       String (Buffer.contents buf)
-    | _ -> raise (Eval_error "clock-format: (seconds [format])"))
+    | _ -> raise (Eval_error "clock-format: (seconds [format])"));
+
+  (* === Env-as-value (Phase 4) === *)
+
+  (* env-lookup: (env key) → value or nil.  Works on Env, Dict, or Nil. *)
+  register "env-lookup" (fun args ->
+    let unwrap = function
+      | Env e -> e
+      | Nil -> make_env ()
+      | _ -> raise (Eval_error "env-lookup: first arg must be an environment") in
+    match args with
+    | [env_val; key] ->
+      let e = unwrap env_val in
+      let k = value_to_string key in
+      if env_has e k then env_get e k else Nil
+    | _ -> raise (Eval_error "env-lookup: (env key)"));
+
+  (* env-extend: (env [key val ...]) → new child env with optional bindings. *)
+  register "env-extend" (fun args ->
+    match args with
+    | [] -> raise (Eval_error "env-extend: requires at least one arg")
+    | env_val :: pairs ->
+      let parent_env = match env_val with
+        | Env e -> e
+        | Nil -> make_env ()
+        | _ -> raise (Eval_error "env-extend: first arg must be an environment") in
+      let child = env_extend parent_env in
+      let rec add_bindings = function
+        | [] -> ()
+        | k :: v :: rest -> ignore (env_bind child (value_to_string k) v); add_bindings rest
+        | [_] -> raise (Eval_error "env-extend: odd number of key-val pairs") in
+      add_bindings pairs;
+      Env child)

hosts/ocaml/lib/sx_runtime.ml

@@ -529,3 +529,4 @@ let jit_try_call f args =
       (match hook f arg_list with Some result -> incr _jit_hit; result | None -> incr _jit_miss; _jit_skip_sentinel)
     | _ -> incr _jit_skip; _jit_skip_sentinel
 
+