R7RS core: call/cc, raise/guard, multi-arity map, cond =>, do iteration

Phase 1 engine step 4 — R7RS compatibility primitives for the CEK evaluator.

call/cc: undelimited continuation capture with separate CallccContinuation
type (distinct from delimited shift/reset continuations). Escape semantics —
invoking k replaces the current continuation entirely.

raise/raise-continuable: proper CEK arg evaluation via raise-eval frame.
Non-continuable raise uses raise-guard frame that errors on handler return.
host-error primitive for safe unhandled exception fallback.

Multi-arity map: (map fn list1 list2 ...) zips multiple lists. Single-list
path unchanged for performance. New multi-map frame type.

cond =>: arrow clause syntax (cond (test => fn)) calls fn with test value.
New cond-arrow frame type.

R7RS do: shape-detecting dispatch — (do ((var init step) ...) (test result) body)
desugars to named let. Existing (do expr1 expr2) sequential form preserved.

integer? primitive, host-error alias. Transpiler fixes: match/case routing,
wildcard _ support, nested match arm handling.

2522/2524 OCaml tests pass (2 pre-existing scope failures from transpiler
match codegen, not related to these changes).

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

hosts/ocaml/browser/sx_browser.ml

@@ -100,7 +100,7 @@ let rec value_to_js (v : value) : Js.Unsafe.any =
          Js.Unsafe.set obj (Js.string k) (value_to_js v)) d;
        Js.Unsafe.inject obj)
   (* Callable values: wrap as JS functions with __sx_handle *)
-  | Lambda _ | NativeFn _ | Continuation _ | VmClosure _ ->
+  | Lambda _ | NativeFn _ | Continuation _ | CallccContinuation _ | VmClosure _ ->
     let handle = alloc_handle v in
     let inner = Js.wrap_callback (fun args_js ->
       try

hosts/ocaml/lib/sx_primitives.ml

@@ -218,6 +218,8 @@ let () =
     match args with [a] -> Bool (is_nil a) | _ -> raise (Eval_error "nil?: 1 arg"));
   register "number?" (fun args ->
     match args with [Number _] -> Bool true | [_] -> Bool false | _ -> raise (Eval_error "number?: 1 arg"));
+  register "integer?" (fun args ->
+    match args with [Number f] -> Bool (Float.is_integer f) | [_] -> Bool false | _ -> raise (Eval_error "integer?: 1 arg"));
   register "string?" (fun args ->
     match args with [String _] -> Bool true | [_] -> Bool false | _ -> raise (Eval_error "string?: 1 arg"));
   register "boolean?" (fun args ->
@@ -708,6 +710,10 @@ let () =
     match args with [String msg] -> raise (Eval_error msg)
     | [a] -> raise (Eval_error (to_string a))
     | _ -> raise (Eval_error "error: 1 arg"));
+  register "host-error" (fun args ->
+    match args with [String msg] -> raise (Eval_error msg)
+    | [a] -> raise (Eval_error (to_string a))
+    | _ -> raise (Eval_error "host-error: 1 arg"));
   register "try-catch" (fun args ->
     match args with
     | [try_fn; catch_fn] ->

hosts/ocaml/lib/sx_runtime.ml

@@ -50,6 +50,8 @@ let sx_call f args =
     Thunk (l.l_body, local)
   | Continuation (k, _) ->
     k (match args with x :: _ -> x | [] -> Nil)
+  | CallccContinuation _ ->
+    raise (Eval_error "callcc continuations must be invoked through the CEK machine")
   | _ ->
     let nargs = List.length args in
     let args_preview = if nargs = 0 then "" else
@@ -103,6 +105,7 @@ let get_val container key =
      | "update-fn" -> f.cf_extra | "head-name" -> f.cf_extra
      | "emitted" -> f.cf_extra2 | "effect-list" -> f.cf_extra2
      | "first-render" -> f.cf_extra2 | "file" -> f.cf_env
+     | "extra" -> f.cf_extra | "extra2" -> f.cf_extra2
      | _ -> Nil)
   | Dict d, String k -> dict_get d k
   | Dict d, Keyword k -> dict_get d k
@@ -323,7 +326,20 @@ let continuation_data v = match v with
   | Continuation (_, None) -> Dict (Hashtbl.create 0)
   | _ -> raise (Eval_error "not a continuation")
 
+(* Callcc (undelimited) continuation support *)
+let callcc_continuation_p v = match v with CallccContinuation _ -> Bool true | _ -> Bool false
+
+let make_callcc_continuation captured =
+  CallccContinuation (sx_to_list captured)
+
+let callcc_continuation_data v = match v with
+  | CallccContinuation frames -> List frames
+  | _ -> raise (Eval_error "not a callcc continuation")
+
 (* Dynamic wind — simplified for OCaml (no async) *)
+let host_error msg =
+  raise (Eval_error (value_to_str msg))
+
 let dynamic_wind_call before body after _env =
   ignore (sx_call before []);
   let result = sx_call body [] in

hosts/ocaml/lib/sx_types.ml

@@ -56,6 +56,7 @@ and value =
   | Macro  of macro
   | Thunk  of value * env
   | Continuation of (value -> value) * dict option
+  | CallccContinuation of value list  (** Undelimited continuation — captured kont frames *)
   | NativeFn of string * (value list -> value)
   | Signal of signal
   | RawHTML of string
@@ -336,6 +337,7 @@ let type_of = function
   | Macro _        -> "macro"
   | Thunk _        -> "thunk"
   | Continuation (_, _) -> "continuation"
+  | CallccContinuation _ -> "continuation"
   | NativeFn _     -> "function"
   | Signal _       -> "signal"
   | RawHTML _      -> "raw-html"
@@ -358,7 +360,7 @@ let is_signal = function
   | _ -> false
 
 let is_callable = function
-  | Lambda _ | NativeFn _ | Continuation (_, _) | VmClosure _ -> true
+  | Lambda _ | NativeFn _ | Continuation (_, _) | CallccContinuation _ | VmClosure _ -> true
   | _ -> false
 
 
@@ -529,6 +531,7 @@ let rec inspect = function
     Printf.sprintf "<%s(%s)>" tag (String.concat ", " m.m_params)
   | Thunk _ -> "<thunk>"
   | Continuation (_, _) -> "<continuation>"
+  | CallccContinuation _ -> "<callcc-continuation>"
   | NativeFn (name, _) -> Printf.sprintf "<native:%s>" name
   | Signal _ -> "<signal>"
   | RawHTML s -> Printf.sprintf "\"<raw-html:%d>\"" (String.length s)