Unify scope mechanism: one world (hashtable stacks everywhere)

Replace continuation-based scope frames with hashtable stacks for all
scope operations. The CEK evaluator's scope/provide/context/emit!/emitted
now use scope-push!/pop!/peek/emit! primitives (registered in
sx_primitives table) instead of walking continuation frames.

This eliminates the two-world problem where the aser used hashtable
stacks (scope-push!/pop!) but eval-expr used continuation frames
(ScopeFrame/ScopeAccFrame). Now both paths share the same mechanism.

Benefits:
- scope/context works inside eval-expr calls (e.g. (str ... (context x)))
- O(1) scope lookup vs O(n) continuation walking
- Simpler — no ScopeFrame/ScopeAccFrame/ProvideFrame creation/dispatch
- VM-compiled code and CEK code both see the same scope state

Also registers scope-push!/pop!/peek/emit!/collect!/collected/
clear-collected! as real primitives (sx_primitives table) so the
transpiled evaluator can call them directly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/bin/sx_server.ml

@@ -129,6 +129,20 @@ let io_counter = ref 0
     scope-push!/pop!) and step-sf-context (via get-primitive "scope-peek"). *)
 let _scope_stacks : (string, value list) Hashtbl.t = Hashtbl.create 8
 
+let () = Sx_primitives.register "scope-push!" (fun args ->
+  match args with
+  | [String name; value] ->
+    let stack = try Hashtbl.find _scope_stacks name with Not_found -> [] in
+    Hashtbl.replace _scope_stacks name (value :: stack); Nil
+  | _ -> Nil)
+
+let () = Sx_primitives.register "scope-pop!" (fun args ->
+  match args with
+  | [String name] ->
+    let stack = try Hashtbl.find _scope_stacks name with Not_found -> [] in
+    (match stack with _ :: rest -> Hashtbl.replace _scope_stacks name rest | [] -> ()); Nil
+  | _ -> Nil)
+
 let () = Sx_primitives.register "scope-peek" (fun args ->
   match args with
   | [String name] ->
@@ -160,6 +174,22 @@ let () = Sx_primitives.register "collected" (fun args ->
     (match stack with List items :: _ -> List items | _ -> List [])
   | _ -> List [])
 
+let () = Sx_primitives.register "scope-emit!" (fun args ->
+  match args with
+  | [String name; value] ->
+    let stack = try Hashtbl.find _scope_stacks name with Not_found -> [] in
+    (match stack with
+     | List items :: rest ->
+       Hashtbl.replace _scope_stacks name (List (items @ [value]) :: rest)
+     | Nil :: rest ->
+       Hashtbl.replace _scope_stacks name (List [value] :: rest)
+     | [] ->
+       (* Lazy root scope *)
+       Hashtbl.replace _scope_stacks name [List [value]]
+     | _ :: _ -> ());
+    Nil
+  | _ -> Nil)
+
 let () = Sx_primitives.register "clear-collected!" (fun args ->
   match args with
   | [String name] ->

hosts/ocaml/lib/sx_ref.ml

@@ -395,23 +395,23 @@ and step_sf_lambda args env kont =
 
 (* step-sf-scope *)
 and step_sf_scope args env kont =
-  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let rest_args = (prim_call "slice" [args; (Number 1.0)]) in let val' = ref (Nil) in let body = ref (Nil) in (let () = ignore ((if sx_truthy ((let _and = (prim_call ">=" [(len (rest_args)); (Number 2.0)]) in if not (sx_truthy _and) then _and else (let _and = (prim_call "=" [(type_of ((first (rest_args)))); (String "keyword")]) in if not (sx_truthy _and) then _and else (prim_call "=" [(keyword_name ((first (rest_args)))); (String "value")])))) then (let () = ignore ((val' := (trampoline ((eval_expr ((nth (rest_args) ((Number 1.0)))) (env)))); Nil)) in (body := (prim_call "slice" [rest_args; (Number 2.0)]); Nil)) else (body := rest_args; Nil))) in (if sx_truthy ((empty_p (!body))) then (make_cek_value (Nil) (env) (kont)) else (if sx_truthy ((prim_call "=" [(len (!body)); (Number 1.0)])) then (make_cek_state ((first (!body))) (env) ((kont_push ((make_scope_acc_frame (name) (!val') ((List [])) (env))) (kont)))) else (make_cek_state ((first (!body))) (env) ((kont_push ((make_scope_acc_frame (name) (!val') ((rest (!body))) (env))) (kont))))))))
+  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let rest_args = (prim_call "slice" [args; (Number 1.0)]) in let val' = ref (Nil) in let body = ref (Nil) in (let () = ignore ((if sx_truthy ((let _and = (prim_call ">=" [(len (rest_args)); (Number 2.0)]) in if not (sx_truthy _and) then _and else (let _and = (prim_call "=" [(type_of ((first (rest_args)))); (String "keyword")]) in if not (sx_truthy _and) then _and else (prim_call "=" [(keyword_name ((first (rest_args)))); (String "value")])))) then (let () = ignore ((val' := (trampoline ((eval_expr ((nth (rest_args) ((Number 1.0)))) (env)))); Nil)) in (body := (prim_call "slice" [rest_args; (Number 2.0)]); Nil)) else (body := rest_args; Nil))) in (let () = ignore ((scope_push (name) (!val'))) in (let result' = ref (Nil) in (let () = ignore ((List.iter (fun expr -> ignore ((result' := (trampoline ((eval_expr (expr) (env)))); Nil))) (sx_to_list !body); Nil)) in (let () = ignore ((scope_pop (name))) in (make_cek_value (!result') (env) (kont))))))))
 
 (* step-sf-provide *)
 and step_sf_provide args env kont =
-  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let val' = (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) in let body = (prim_call "slice" [args; (Number 2.0)]) in (if sx_truthy ((empty_p (body))) then (make_cek_value (Nil) (env) (kont)) else (if sx_truthy ((prim_call "=" [(len (body)); (Number 1.0)])) then (make_cek_state ((first (body))) (env) ((kont_push ((make_provide_frame (name) (val') ((List [])) (env))) (kont)))) else (make_cek_state ((first (body))) (env) ((kont_push ((make_provide_frame (name) (val') ((rest (body))) (env))) (kont)))))))
+  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let val' = (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) in let body = (prim_call "slice" [args; (Number 2.0)]) in (let () = ignore ((scope_push (name) (val'))) in (let result' = ref (Nil) in (let () = ignore ((List.iter (fun expr -> ignore ((result' := (trampoline ((eval_expr (expr) (env)))); Nil))) (sx_to_list body); Nil)) in (let () = ignore ((scope_pop (name))) in (make_cek_value (!result') (env) (kont)))))))
 
 (* step-sf-context *)
 and step_sf_context args env kont =
-  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let default_val = (if sx_truthy ((prim_call ">=" [(len (args)); (Number 2.0)])) then (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) else Nil) in (let stack_val = (if sx_truthy ((is_primitive ((String "scope-peek")))) then (cek_call ((get_primitive ((String "scope-peek")))) (List [name])) else Nil) in (if sx_truthy ((Bool (not (sx_truthy ((is_nil (stack_val))))))) then (make_cek_value (stack_val) (env) (kont)) else (let frame = (kont_find_provide (kont) (name)) in (if sx_truthy (frame) then (make_cek_value ((get (frame) ((String "value")))) (env) (kont)) else (if sx_truthy ((prim_call ">=" [(len (args)); (Number 2.0)])) then (make_cek_value (default_val) (env) (kont)) else (raise (Eval_error (value_to_str (String (sx_str [(String "No provider for: "); name])))))))))))
+  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let default_val = (if sx_truthy ((prim_call ">=" [(len (args)); (Number 2.0)])) then (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) else Nil) in let val' = (scope_peek (name)) in (make_cek_value ((if sx_truthy ((is_nil (val'))) then default_val else val')) (env) (kont)))
 
 (* step-sf-emit *)
 and step_sf_emit args env kont =
-  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let val' = (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) in let frame = (kont_find_scope_acc (kont) (name)) in (if sx_truthy (frame) then (let () = ignore ((sx_append_b (get (frame) ((String "emitted"))) val')) in (make_cek_value (Nil) (env) (kont))) else (raise (Eval_error (value_to_str (String (sx_str [(String "No scope for emit!: "); name])))))))
+  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let val' = (trampoline ((eval_expr ((nth (args) ((Number 1.0)))) (env)))) in (let () = ignore ((scope_emit (name) (val'))) in (make_cek_value (Nil) (env) (kont))))
 
 (* step-sf-emitted *)
 and step_sf_emitted args env kont =
-  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let frame = (kont_find_scope_acc (kont) (name)) in (if sx_truthy (frame) then (make_cek_value ((get (frame) ((String "emitted")))) (env) (kont)) else (raise (Eval_error (value_to_str (String (sx_str [(String "No scope for emitted: "); name])))))))
+  (let name = (trampoline ((eval_expr ((first (args))) (env)))) in let val' = (scope_peek (name)) in (make_cek_value ((if sx_truthy ((is_nil (val'))) then (List []) else val')) (env) (kont)))
 
 (* step-sf-reset *)
 and step_sf_reset args env kont =

hosts/ocaml/lib/sx_runtime.ml

@@ -315,11 +315,13 @@ let dynamic_wind_call before body after _env =
   ignore (sx_call after []);
   result
 
-(* Scope stack stubs — delegated to primitives when available *)
-let scope_push name value = prim_call "collect!" [name; value]
-let scope_pop _name = Nil
-let provide_push name value = ignore name; ignore value; Nil
-let provide_pop _name = Nil
+(* Scope stack — all delegated to primitives registered in sx_server.ml *)
+let scope_push name value = prim_call "scope-push!" [name; value]
+let scope_pop name = prim_call "scope-pop!" [name]
+let scope_peek name = prim_call "scope-peek" [name]
+let scope_emit name value = prim_call "scope-emit!" [name; value]
+let provide_push name value = prim_call "scope-push!" [name; value]
+let provide_pop name = prim_call "scope-pop!" [name]
 
 (* Custom special forms registry — mutable dict *)
 let custom_special_forms = Dict (Hashtbl.create 4)

hosts/ocaml/transpiler.sx

@@ -120,6 +120,8 @@
   "emitted" "sx_emitted"
   "scope-push!" "scope_push"
   "scope-pop!" "scope_pop"
+  "scope-peek" "scope_peek"
+  "scope-emit!" "scope_emit"
   "provide-push!" "provide_push"
   "provide-pop!" "provide_pop"
   "sx-serialize" "sx_serialize"