spec: promises — delay/force/delay-force/make-promise/promise?

25 tests pass on OCaml (4357 total) and JS. Promise represented as
mutable dict {:_promise true :forced :thunk :value}; delay-force
adds :_iterative for chain-following semantics.

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

hosts/ocaml/bin/run_tests.ml

@@ -1141,6 +1141,26 @@ let make_test_env () =
       Sx_ref.cek_call consumer (List spread)
     | _ -> raise (Eval_error "call-with-values: expected 2 args"));
 
+  bind "promise?" (fun args ->
+    match args with
+    | [v] -> Bool (Sx_ref.is_promise v)
+    | _ -> Bool false);
+
+  bind "make-promise" (fun args ->
+    match args with
+    | [v] ->
+      let d = Hashtbl.create 4 in
+      Hashtbl.replace d "_promise" (Bool true);
+      Hashtbl.replace d "forced" (Bool true);
+      Hashtbl.replace d "value" v;
+      Dict d
+    | _ -> Nil);
+
+  bind "force" (fun args ->
+    match args with
+    | [p] -> Sx_ref.force_promise p
+    | _ -> Nil);
+
   env
 
 (* ====================================================================== *)

hosts/ocaml/lib/sx_ref.ml

@@ -1161,4 +1161,59 @@ let () = ignore (register_special_form (String "define-values")
     | [args; env] -> sf_define_values args env
     | _ -> Nil)))
 
+(* Phase 9: Promises — delay/force/delay-force/make-promise/promise? *)
+
+let make_promise_dict ?(iterative=false) thunk =
+  let d = Hashtbl.create 4 in
+  Hashtbl.replace d "_promise" (Bool true);
+  Hashtbl.replace d "forced" (Bool false);
+  Hashtbl.replace d "thunk" thunk;
+  Hashtbl.replace d "value" Nil;
+  if iterative then Hashtbl.replace d "_iterative" (Bool true);
+  Dict d
+
+let sf_delay args env_val =
+  let expr = match args with List (e :: _) -> e | _ -> Nil in
+  let thunk = make_lambda (List []) expr env_val in
+  make_promise_dict thunk
+
+let sf_delay_force args env_val =
+  let expr = match args with List (e :: _) -> e | _ -> Nil in
+  let thunk = make_lambda (List []) expr env_val in
+  make_promise_dict ~iterative:true thunk
+
+let is_promise v =
+  match v with
+  | Dict d -> (match Hashtbl.find_opt d "_promise" with Some (Bool true) -> true | _ -> false)
+  | _ -> false
+
+let rec force_promise p =
+  if not (is_promise p) then p
+  else match p with
+  | Dict d ->
+    (match Hashtbl.find_opt d "forced" with
+     | Some (Bool true) ->
+       (match Hashtbl.find_opt d "value" with Some v -> v | None -> Nil)
+     | _ ->
+       let thunk = (match Hashtbl.find_opt d "thunk" with Some t -> t | None -> Nil) in
+       let result = cek_call thunk (List []) in
+       let iterative = (match Hashtbl.find_opt d "_iterative" with Some (Bool true) -> true | _ -> false) in
+       let final_val = if iterative && is_promise result then force_promise result else result in
+       Hashtbl.replace d "forced" (Bool true);
+       Hashtbl.replace d "value" final_val;
+       final_val)
+  | _ -> p
+
+let () = ignore (register_special_form (String "delay")
+  (NativeFn ("delay", fun call_args ->
+    match call_args with
+    | [args; env] -> sf_delay args env
+    | _ -> Nil)))
+
+let () = ignore (register_special_form (String "delay-force")
+  (NativeFn ("delay-force", fun call_args ->
+    match call_args with
+    | [args; env] -> sf_delay_force args env
+    | _ -> Nil)))
+