scheme: Phase 4 standard env + set! bugfix + 78 tests

lib/scheme/runtime.sx — full R7RS-base surface:

- Arithmetic: variadic +/-/*//, abs, min, max, modulo, quotient,
  remainder. Predicates zero?/positive?/negative?.
- Comparison: chained =/</>/<=/>=.
- Type predicates: number?/boolean?/symbol?/string?/char?/vector?/
  null?/pair?/procedure?/not.
- List: cons/car/cdr/list/length/reverse/append.
- Higher-order: map/filter/fold-left/fold-right/for-each/apply.
  These re-enter scheme-apply to invoke user-supplied procs.
- String: string-length/string=?/string-append/substring.
- Char: char=?.
- Vector: vector/vector-length/vector-ref/vector->list/list->vector/
  make-vector.
- Equality: eqv?/equal?/eq? (all = under the hood for now).

Built via small adapters: scm-unary, scm-binary, scm-fold (variadic
left-fold with identity + one-arity special), scm-chain (n-ary
chained comparison).

**Bugfix in eval.sx set! handler.** The :else branch had two
expressions `(dict-set! ...) val` — SX cond branches don't run
multiple expressions, they return nil silently (or evaluate only
the first, depending on shape). Wrapped in (begin ...) to force
sequential execution. This fix also unblocks 4 set!-dependent
tests in lib/scheme/tests/syntax.sx that were silently raising
during load (and thus not counted) — syntax test count jumps
from 45 → 49.

Classic programs verified:
- factorial 10 → 3628800
- fib 10 → 55
- recursive list reverse → working
- sum of squares via fold-left + map → 55

212 total Scheme tests: parse 62 + eval 23 + syntax 49 + runtime 78.
All green.

The env-as-value section in runtime tests demonstrates
scheme-standard-env IS a refl-env? — kit primitives operate on it
directly, confirming the third-consumer adoption with zero adapter.

lib/scheme/eval.sx

@@ -0,0 +1,431 @@
+;; lib/scheme/eval.sx — R7RS-small evaluator (Phase 2 skeleton).
+;;
+;; The evaluator walks parsed AST applying R7RS semantics:
+;;   - numbers, booleans, characters, vectors, strings self-evaluate
+;;   - symbols look up in the lexical env
+;;   - lists with a syntactic-operator head dispatch to native handler
+;;   - lists with an applicative head: eval head + args, then call
+;;
+;; Phase 2 covers literals, symbol lookup, and `quote`. The full
+;; suite of syntactic operators (if/lambda/define/let/...) lands in
+;; Phase 3.
+;;
+;; Environment representation
+;; --------------------------
+;; Scheme is the THIRD CONSUMER for `lib/guest/reflective/env.sx`.
+;; It uses the canonical mutable wire shape `{:refl-tag :env
+;; :bindings DICT :parent ENV-OR-NIL}` directly — no adapter cfg —
+;; because Scheme's lexical-scope semantics match the kit's defaults
+;; exactly. Compare with Tcl (functional updates, level field) and
+;; Smalltalk (rich frame metadata) which DID need cfg adapters.
+;;
+;; Public API
+;;   (scheme-eval EXPR ENV)         — primary entry
+;;   (scheme-make-env)              — fresh top-level env
+;;   (scheme-extend-env P)          — child env
+;;   (scheme-env-bind! E N V)
+;;   (scheme-env-lookup E N)
+;;
+;; Consumes: lib/guest/reflective/env.sx; lib/scheme/parser.sx
+;;   (scheme-string?, scheme-char?, scheme-vector?).
+
+;; Thin wrappers over the kit. Scheme uses the canonical shape with
+;; no cfg, so these are direct aliases.
+(define scheme-make-env refl-make-env)
+(define scheme-extend-env refl-extend-env)
+(define scheme-env? refl-env?)
+(define scheme-env-bind! refl-env-bind!)
+(define scheme-env-has? refl-env-has?)
+(define scheme-env-lookup refl-env-lookup)
+
+;; ── self-evaluating values ───────────────────────────────────────
+
+(define
+  scheme-self-eval?
+  (fn
+    (v)
+    (or
+      (number? v)
+      (boolean? v)
+      (nil? v)
+      (scheme-string? v)
+      (scheme-char? v)
+      (scheme-vector? v))))
+
+;; ── syntactic-operator table ─────────────────────────────────────
+;; Each operator is a fn (args env) that returns the result of the
+;; special form. Phase 2 only handles `quote`; Phase 3 fills out the
+;; rest. The table-driven dispatch keeps the eval body small and
+;; makes new operators easy to add.
+
+(define scheme-syntactic-ops {})
+
+(define
+  scheme-define-op!
+  (fn (name handler) (dict-set! scheme-syntactic-ops name handler)))
+
+(define
+  scheme-syntactic-op?
+  (fn (name) (dict-has? scheme-syntactic-ops name)))
+
+;; quote — return arg unevaluated.
+(scheme-define-op!
+  "quote"
+  (fn
+    (args env)
+    (cond
+      ((not (= (length args) 1))
+        (error "quote: expects exactly 1 argument"))
+      (:else (first args)))))
+
+;; if — (if TEST CONSEQUENT) or (if TEST CONSEQUENT ALTERNATE).
+;; Scheme truthiness: only #f is false; everything else (incl. nil/empty
+;; list) is truthy. Match SX's `if` semantics where possible.
+(scheme-define-op! "if"
+  (fn (args env)
+    (cond
+      ((< (length args) 2)
+        (error "if: expects (test then [else])"))
+      (:else
+        (let ((test-val (scheme-eval (first args) env)))
+          (cond
+            ((not (= test-val false))
+              (scheme-eval (nth args 1) env))
+            ((>= (length args) 3)
+              (scheme-eval (nth args 2) env))
+            (:else nil)))))))
+
+;; set! — mutate an existing binding by walking the env chain.
+(scheme-define-op! "set!"
+  (fn (args env)
+    (cond
+      ((not (= (length args) 2))
+        (error "set!: expects (set! name expr)"))
+      ((not (string? (first args)))
+        (error "set!: name must be a symbol"))
+      (:else
+        (let ((name (first args))
+              (val (scheme-eval (nth args 1) env)))
+          (let ((src (refl-env-find-frame env name)))
+            (cond
+              ((nil? src)
+                (error (str "set!: unbound variable: " name)))
+              (:else
+                (begin
+                  (dict-set! (get src :bindings) name val)
+                  val)))))))))
+
+;; define — top-level or internal binding. (define name expr) or
+;; (define (name . formals) body...) the latter being lambda sugar.
+(scheme-define-op! "define"
+  (fn (args env)
+    (cond
+      ((< (length args) 2)
+        (error "define: expects (define name expr) or (define (name . formals) body)"))
+      ((string? (first args))
+        ;; (define name expr)
+        (let ((val (scheme-eval (nth args 1) env)))
+          (scheme-env-bind! env (first args) val)
+          val))
+      ((list? (first args))
+        ;; (define (name . formals) body...) — sugar
+        (let ((header (first args))
+              (body (rest args)))
+          (cond
+            ((= (length header) 0)
+              (error "define: malformed function header"))
+            (:else
+              (let ((name (first header))
+                    (formals (rest header)))
+                (let ((closure (scheme-make-closure formals nil body env)))
+                  (scheme-env-bind! env name closure)
+                  closure))))))
+      (:else (error "define: malformed form")))))
+
+;; begin — evaluate each expression in sequence, return the last.
+(scheme-define-op! "begin"
+  (fn (args env)
+    (cond
+      ((or (nil? args) (= (length args) 0)) nil)
+      (:else (scheme-eval-body args env)))))
+
+(define scheme-eval-body
+  (fn (forms env)
+    (cond
+      ((= (length forms) 1) (scheme-eval (first forms) env))
+      (:else
+        (begin
+          (scheme-eval (first forms) env)
+          (scheme-eval-body (rest forms) env))))))
+
+;; lambda — (lambda formals body...) where formals is one of:
+;;   ()             — no args
+;;   (a b c)        — fixed-arity
+;;   name           — bare symbol; binds all args as a list
+;; Dotted-pair tail (a b . rest) deferred until parser support lands.
+(scheme-define-op! "lambda"
+  (fn (args env)
+    (cond
+      ((< (length args) 2)
+        (error "lambda: expects (lambda formals body...)"))
+      (:else
+        (let ((formals (first args))
+              (body (rest args)))
+          (cond
+            ;; bare symbol: collect-all-args
+            ((string? formals)
+              (scheme-make-closure (list) formals body env))
+            ;; flat list: each must be a symbol
+            ((list? formals)
+              (cond
+                ((not (scm-formals-ok? formals))
+                  (error "lambda: formals must be symbols"))
+                (:else
+                  (scheme-make-closure formals nil body env))))
+            (:else (error "lambda: invalid formals"))))))))
+
+(define scm-formals-ok?
+  (fn (formals)
+    (cond
+      ((or (nil? formals) (= (length formals) 0)) true)
+      ((string? (first formals)) (scm-formals-ok? (rest formals)))
+      (:else false))))
+
+(define scheme-make-closure
+  (fn (params rest-name body env)
+    {:scm-tag :closure
+     :params params
+     :rest rest-name
+     :body body
+     :env env}))
+
+;; ── let / let* — bindings in a fresh child env ───────────────────
+
+(define scm-bind-let-vals!
+  (fn (local bindings dyn-env)
+    (cond
+      ((or (nil? bindings) (= (length bindings) 0)) nil)
+      (:else
+        (let ((b (first bindings)))
+          (cond
+            ((not (and (list? b) (= (length b) 2)))
+              (error "let: each binding must be (name expr)"))
+            ((not (string? (first b)))
+              (error "let: binding name must be a symbol"))
+            (:else
+              (begin
+                (scheme-env-bind! local (first b)
+                                  (scheme-eval (nth b 1) dyn-env))
+                (scm-bind-let-vals! local (rest bindings) dyn-env)))))))))
+
+(scheme-define-op! "let"
+  (fn (args env)
+    (cond
+      ((< (length args) 2)
+        (error "let: expects (bindings body...)"))
+      ((not (list? (first args)))
+        (error "let: bindings must be a list"))
+      (:else
+        (let ((local (scheme-extend-env env)))
+          (scm-bind-let-vals! local (first args) env)
+          (scheme-eval-body (rest args) local))))))
+
+;; let* — sequential let; each binding sees earlier ones.
+(define scm-let*-step
+  (fn (bindings env body)
+    (cond
+      ((or (nil? bindings) (= (length bindings) 0))
+        (scheme-eval-body body env))
+      (:else
+        (let ((b (first bindings)))
+          (cond
+            ((not (and (list? b) (= (length b) 2)))
+              (error "let*: each binding must be (name expr)"))
+            (:else
+              (let ((child (scheme-extend-env env)))
+                (scheme-env-bind! child (first b)
+                                  (scheme-eval (nth b 1) env))
+                (scm-let*-step (rest bindings) child body)))))))))
+
+(scheme-define-op! "let*"
+  (fn (args env)
+    (cond
+      ((< (length args) 2)
+        (error "let*: expects (bindings body...)"))
+      ((not (list? (first args)))
+        (error "let*: bindings must be a list"))
+      (:else (scm-let*-step (first args) env (rest args))))))
+
+;; ── cond / when / unless ─────────────────────────────────────────
+
+(define scm-cond-clauses
+  (fn (clauses env)
+    (cond
+      ((or (nil? clauses) (= (length clauses) 0)) nil)
+      (:else
+        (let ((clause (first clauses)))
+          (cond
+            ((not (list? clause))
+              (error "cond: each clause must be a list"))
+            ((= (length clause) 0)
+              (error "cond: empty clause"))
+            ((and (string? (first clause)) (= (first clause) "else"))
+              (scheme-eval-body (rest clause) env))
+            (:else
+              (let ((test-val (scheme-eval (first clause) env)))
+                (cond
+                  ((not (= test-val false))
+                    (cond
+                      ((= (length clause) 1) test-val)
+                      (:else (scheme-eval-body (rest clause) env))))
+                  (:else (scm-cond-clauses (rest clauses) env)))))))))))
+
+(scheme-define-op! "cond"
+  (fn (args env) (scm-cond-clauses args env)))
+
+(scheme-define-op! "when"
+  (fn (args env)
+    (cond
+      ((< (length args) 1) (error "when: expects (when test body...)"))
+      (:else
+        (let ((v (scheme-eval (first args) env)))
+          (cond
+            ((= v false) nil)
+            (:else (scheme-eval-body (rest args) env))))))))
+
+(scheme-define-op! "unless"
+  (fn (args env)
+    (cond
+      ((< (length args) 1)
+        (error "unless: expects (unless test body...)"))
+      (:else
+        (let ((v (scheme-eval (first args) env)))
+          (cond
+            ((= v false) (scheme-eval-body (rest args) env))
+            (:else nil)))))))
+
+;; ── and / or — short-circuit boolean operators ──────────────────
+
+(define scm-and-step
+  (fn (args env)
+    (cond
+      ((or (nil? args) (= (length args) 0)) true)
+      ((= (length args) 1) (scheme-eval (first args) env))
+      (:else
+        (let ((v (scheme-eval (first args) env)))
+          (cond
+            ((= v false) false)
+            (:else (scm-and-step (rest args) env))))))))
+
+(scheme-define-op! "and"
+  (fn (args env) (scm-and-step args env)))
+
+(define scm-or-step
+  (fn (args env)
+    (cond
+      ((or (nil? args) (= (length args) 0)) false)
+      ((= (length args) 1) (scheme-eval (first args) env))
+      (:else
+        (let ((v (scheme-eval (first args) env)))
+          (cond
+            ((not (= v false)) v)
+            (:else (scm-or-step (rest args) env))))))))
+
+(scheme-define-op! "or"
+  (fn (args env) (scm-or-step args env)))
+
+;; ── eval-args helper ─────────────────────────────────────────────
+
+(define
+  scheme-eval-args
+  (fn
+    (args env)
+    (cond
+      ((or (nil? args) (= (length args) 0)) (list))
+      (:else
+        (cons
+          (scheme-eval (first args) env)
+          (scheme-eval-args (rest args) env))))))
+
+;; ── main eval ────────────────────────────────────────────────────
+
+(define
+  scheme-eval
+  (fn
+    (expr env)
+    (cond
+      ((scheme-self-eval? expr) expr)
+      ((string? expr) (scheme-env-lookup env expr))
+      ((list? expr)
+        (cond
+          ((= (length expr) 0)
+            (error "scheme-eval: empty application"))
+          (:else
+            (let
+              ((head (first expr)) (rest-args (rest expr)))
+              (cond
+                ((and (string? head) (scheme-syntactic-op? head))
+                  ((get scheme-syntactic-ops head) rest-args env))
+                (:else
+                  (let
+                    ((proc (scheme-eval head env))
+                      (vals (scheme-eval-args rest-args env)))
+                    (scheme-apply proc vals))))))))
+      (:else (error (str "scheme-eval: unknown form: " expr))))))
+
+;; ── apply ────────────────────────────────────────────────────────
+;; Phase 2 only knows about HOST procedures (SX fns) bound in the
+;; env as primitives. Phase 3 adds Scheme `lambda` closures.
+
+(define
+  scheme-apply
+  (fn
+    (proc args)
+    (cond
+      ((callable? proc) (proc args))
+      ((and (dict? proc) (= (get proc :scm-tag) :closure))
+        (scheme-apply-closure proc args))
+      (:else (error (str "scheme-eval: not a procedure: " proc))))))
+
+;; Apply a Scheme closure: bind formals + rest, eval body in
+;; (extend static-env), return value of last form.
+(define scheme-apply-closure
+  (fn (proc args)
+    (let ((local (scheme-extend-env (get proc :env)))
+          (params (get proc :params))
+          (rest-name (get proc :rest))
+          (body (get proc :body)))
+      (begin
+        (scm-bind-params! local params args rest-name)
+        (scheme-eval-body body local)))))
+
+(define scm-bind-params!
+  (fn (env params args rest-name)
+    (cond
+      ;; No more formals: maybe bind the rest, else check arity.
+      ((or (nil? params) (= (length params) 0))
+        (cond
+          ((not (nil? rest-name))
+            (scheme-env-bind! env rest-name args))
+          ((or (nil? args) (= (length args) 0)) nil)
+          (:else (error "lambda: too many arguments"))))
+      ;; Out of args but still have formals → arity error.
+      ((or (nil? args) (= (length args) 0))
+        (error "lambda: too few arguments"))
+      (:else
+        (begin
+          (scheme-env-bind! env (first params) (first args))
+          (scm-bind-params! env (rest params) (rest args) rest-name))))))
+
+;; Evaluate a program (sequence of forms), returning the last value.
+(define
+  scheme-eval-program
+  (fn
+    (forms env)
+    (cond
+      ((or (nil? forms) (= (length forms) 0)) nil)
+      ((= (length forms) 1) (scheme-eval (first forms) env))
+      (:else
+        (begin
+          (scheme-eval (first forms) env)
+          (scheme-eval-program (rest forms) env))))))

lib/scheme/runtime.sx

@@ -0,0 +1,513 @@
+;; lib/scheme/runtime.sx — R7RS-small standard environment.
+;;
+;; Builds scheme-standard-env from scheme-make-env, populating it with
+;; arithmetic, comparison, type predicates, list/pair/vector/string/char
+;; primitives, and the higher-order combinators (map/filter/fold).
+;;
+;; Primitives are bound as SX fns taking a list of evaluated arguments.
+;; Combinators that re-enter the evaluator (map, filter, fold, apply,
+;; for-each) call `scheme-apply` directly on user-supplied procedures.
+;;
+;; Public API
+;;   (scheme-standard-env)  — fresh env with the full R7RS-base surface
+;;
+;; Consumes: lib/scheme/eval.sx (scheme-apply, scheme-make-env,
+;;           scheme-env-bind!, scheme-string?, scheme-char?,
+;;           scheme-vector?, scheme-vector-elements,
+;;           scheme-string-value, scheme-char-value,
+;;           scheme-string-make, scheme-char-make,
+;;           scheme-vector-make).
+
+;; ── Arity / fold helpers ─────────────────────────────────────────
+
+(define
+  scm-unary
+  (fn
+    (name f)
+    (fn
+      (args)
+      (cond
+        ((not (= (length args) 1))
+          (error (str name ": expects 1 argument")))
+        (:else (f (first args)))))))
+
+(define
+  scm-binary
+  (fn
+    (name f)
+    (fn
+      (args)
+      (cond
+        ((not (= (length args) 2))
+          (error (str name ": expects 2 arguments")))
+        (:else (f (first args) (nth args 1)))))))
+
+;; Variadic left-fold helper. zero-id is the identity (`(+)` → 0).
+;; one-fn handles single-arg case (`(- x)` negates).
+(define
+  scm-fold-step
+  (fn
+    (f acc rest-args)
+    (cond
+      ((or (nil? rest-args) (= (length rest-args) 0)) acc)
+      (:else (scm-fold-step f (f acc (first rest-args)) (rest rest-args))))))
+
+(define
+  scm-fold
+  (fn
+    (name f zero-id one-fn)
+    (fn
+      (args)
+      (cond
+        ((= (length args) 0) zero-id)
+        ((= (length args) 1) (one-fn (first args)))
+        (:else (scm-fold-step f (first args) (rest args)))))))
+
+;; n-ary chained comparison: (< 1 2 3) ≡ (< 1 2) ∧ (< 2 3).
+(define
+  scm-chain-step
+  (fn
+    (cmp prev rest-args)
+    (cond
+      ((or (nil? rest-args) (= (length rest-args) 0)) true)
+      (:else
+        (let
+          ((next (first rest-args)))
+          (cond
+            ((cmp prev next) (scm-chain-step cmp next (rest rest-args)))
+            (:else false)))))))
+
+(define
+  scm-chain
+  (fn
+    (name cmp)
+    (fn
+      (args)
+      (cond
+        ((< (length args) 2)
+          (error (str name ": expects at least 2 arguments")))
+        (:else (scm-chain-step cmp (first args) (rest args)))))))
+
+;; ── List helpers ─────────────────────────────────────────────────
+
+(define
+  scm-list-append
+  (fn
+    (xs ys)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) ys)
+      (:else (cons (first xs) (scm-list-append (rest xs) ys))))))
+
+(define
+  scm-list-reverse-step
+  (fn
+    (xs acc)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) acc)
+      (:else (scm-list-reverse-step (rest xs) (cons (first xs) acc))))))
+
+(define
+  scm-all-lists?
+  (fn
+    (xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) true)
+      ((list? (first xs)) (scm-all-lists? (rest xs)))
+      (:else false))))
+
+(define
+  scm-append-all
+  (fn
+    (lists)
+    (cond
+      ((or (nil? lists) (= (length lists) 0)) (list))
+      ((= (length lists) 1) (first lists))
+      (:else (scm-list-append (first lists) (scm-append-all (rest lists)))))))
+
+;; ── Map / Filter / Fold ──────────────────────────────────────────
+;; These call scheme-apply directly so closures and primitives both work.
+
+(define
+  scm-map-step
+  (fn
+    (proc xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) (list))
+      (:else
+        (cons
+          (scheme-apply proc (list (first xs)))
+          (scm-map-step proc (rest xs)))))))
+
+(define
+  scm-filter-step
+  (fn
+    (pred xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) (list))
+      (:else
+        (let
+          ((keep? (scheme-apply pred (list (first xs)))))
+          (cond
+            ((not (= keep? false))
+              (cons (first xs) (scm-filter-step pred (rest xs))))
+            (:else (scm-filter-step pred (rest xs)))))))))
+
+(define
+  scm-fold-left-step
+  (fn
+    (proc acc xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) acc)
+      (:else
+        (scm-fold-left-step
+          proc
+          (scheme-apply proc (list acc (first xs)))
+          (rest xs))))))
+
+(define
+  scm-fold-right-step
+  (fn
+    (proc init xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) init)
+      (:else
+        (scheme-apply
+          proc
+          (list (first xs) (scm-fold-right-step proc init (rest xs))))))))
+
+(define
+  scm-for-each-step
+  (fn
+    (proc xs)
+    (cond
+      ((or (nil? xs) (= (length xs) 0)) nil)
+      (:else
+        (begin
+          (scheme-apply proc (list (first xs)))
+          (scm-for-each-step proc (rest xs)))))))
+
+;; ── Vector helpers ──────────────────────────────────────────────
+
+(define
+  scm-make-vector-step
+  (fn
+    (n fill acc)
+    (cond
+      ((<= n 0) acc)
+      (:else (scm-make-vector-step (- n 1) fill (cons fill acc))))))
+
+;; ── Standard env ─────────────────────────────────────────────────
+
+(define
+  scheme-standard-env
+  (fn
+    ()
+    (let
+      ((env (scheme-make-env)))
+      (scheme-env-bind!
+        env
+        "+"
+        (scm-fold "+" (fn (a b) (+ a b)) 0 (fn (x) x)))
+      (scheme-env-bind!
+        env
+        "-"
+        (scm-fold
+          "-"
+          (fn (a b) (- a b))
+          0
+          (fn (x) (- 0 x))))
+      (scheme-env-bind!
+        env
+        "*"
+        (scm-fold "*" (fn (a b) (* a b)) 1 (fn (x) x)))
+      (scheme-env-bind!
+        env
+        "/"
+        (scm-fold
+          "/"
+          (fn (a b) (/ a b))
+          1
+          (fn (x) (/ 1 x))))
+      (scheme-env-bind!
+        env
+        "abs"
+        (scm-unary
+          "abs"
+          (fn (n) (if (< n 0) (- 0 n) n))))
+      (scheme-env-bind!
+        env
+        "min"
+        (scm-fold "min" (fn (a b) (if (< a b) a b)) nil (fn (x) x)))
+      (scheme-env-bind!
+        env
+        "max"
+        (scm-fold "max" (fn (a b) (if (< a b) b a)) nil (fn (x) x)))
+      (scheme-env-bind!
+        env
+        "modulo"
+        (scm-binary "modulo" (fn (a b) (- a (* b (floor (/ a b)))))))
+      (scheme-env-bind!
+        env
+        "quotient"
+        (scm-binary "quotient" (fn (a b) (floor (/ a b)))))
+      (scheme-env-bind!
+        env
+        "remainder"
+        (scm-binary "remainder" (fn (a b) (- a (* b (floor (/ a b)))))))
+      (scheme-env-bind!
+        env
+        "zero?"
+        (scm-unary "zero?" (fn (n) (= n 0))))
+      (scheme-env-bind!
+        env
+        "positive?"
+        (scm-unary "positive?" (fn (n) (> n 0))))
+      (scheme-env-bind!
+        env
+        "negative?"
+        (scm-unary "negative?" (fn (n) (< n 0))))
+      (scheme-env-bind! env "=" (scm-chain "=" (fn (a b) (= a b))))
+      (scheme-env-bind! env "<" (scm-chain "<" (fn (a b) (< a b))))
+      (scheme-env-bind! env ">" (scm-chain ">" (fn (a b) (> a b))))
+      (scheme-env-bind! env "<=" (scm-chain "<=" (fn (a b) (<= a b))))
+      (scheme-env-bind! env ">=" (scm-chain ">=" (fn (a b) (>= a b))))
+      (scheme-env-bind!
+        env
+        "number?"
+        (scm-unary "number?" (fn (v) (number? v))))
+      (scheme-env-bind!
+        env
+        "boolean?"
+        (scm-unary "boolean?" (fn (v) (boolean? v))))
+      (scheme-env-bind!
+        env
+        "symbol?"
+        (scm-unary "symbol?" (fn (v) (string? v))))
+      (scheme-env-bind!
+        env
+        "string?"
+        (scm-unary "string?" (fn (v) (scheme-string? v))))
+      (scheme-env-bind!
+        env
+        "char?"
+        (scm-unary "char?" (fn (v) (scheme-char? v))))
+      (scheme-env-bind!
+        env
+        "vector?"
+        (scm-unary "vector?" (fn (v) (scheme-vector? v))))
+      (scheme-env-bind!
+        env
+        "null?"
+        (scm-unary
+          "null?"
+          (fn
+            (v)
+            (or (nil? v) (and (list? v) (= (length v) 0))))))
+      (scheme-env-bind!
+        env
+        "pair?"
+        (scm-unary
+          "pair?"
+          (fn (v) (and (list? v) (> (length v) 0)))))
+      (scheme-env-bind!
+        env
+        "procedure?"
+        (scm-unary
+          "procedure?"
+          (fn
+            (v)
+            (or
+              (callable? v)
+              (and (dict? v) (= (get v :scm-tag) :closure))))))
+      (scheme-env-bind! env "not" (scm-unary "not" (fn (v) (= v false))))
+      (scheme-env-bind!
+        env
+        "cons"
+        (scm-binary "cons" (fn (a b) (cons a b))))
+      (scheme-env-bind!
+        env
+        "car"
+        (scm-unary
+          "car"
+          (fn
+            (xs)
+            (cond
+              ((or (nil? xs) (and (list? xs) (= (length xs) 0)))
+                (error "car: empty list"))
+              (:else (first xs))))))
+      (scheme-env-bind!
+        env
+        "cdr"
+        (scm-unary
+          "cdr"
+          (fn
+            (xs)
+            (cond
+              ((or (nil? xs) (and (list? xs) (= (length xs) 0)))
+                (error "cdr: empty list"))
+              (:else (rest xs))))))
+      (scheme-env-bind! env "list" (fn (args) args))
+      (scheme-env-bind!
+        env
+        "length"
+        (scm-unary "length" (fn (xs) (length xs))))
+      (scheme-env-bind!
+        env
+        "reverse"
+        (scm-unary "reverse" (fn (xs) (scm-list-reverse-step xs (list)))))
+      (scheme-env-bind!
+        env
+        "append"
+        (fn
+          (args)
+          (cond
+            ((scm-all-lists? args) (scm-append-all args))
+            (:else (error "append: all arguments must be lists")))))
+      (scheme-env-bind!
+        env
+        "map"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 2))
+              (error "map: expects (proc list)"))
+            (:else (scm-map-step (first args) (nth args 1))))))
+      (scheme-env-bind!
+        env
+        "filter"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 2))
+              (error "filter: expects (pred list)"))
+            (:else (scm-filter-step (first args) (nth args 1))))))
+      (scheme-env-bind!
+        env
+        "fold-left"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 3))
+              (error "fold-left: expects (proc init list)"))
+            (:else
+              (scm-fold-left-step
+                (first args)
+                (nth args 1)
+                (nth args 2))))))
+      (scheme-env-bind!
+        env
+        "fold-right"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 3))
+              (error "fold-right: expects (proc init list)"))
+            (:else
+              (scm-fold-right-step
+                (first args)
+                (nth args 1)
+                (nth args 2))))))
+      (scheme-env-bind!
+        env
+        "for-each"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 2))
+              (error "for-each: expects (proc list)"))
+            (:else (scm-for-each-step (first args) (nth args 1))))))
+      (scheme-env-bind!
+        env
+        "apply"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 2))
+              (error "apply: expects (proc args-list)"))
+            (:else (scheme-apply (first args) (nth args 1))))))
+      (scheme-env-bind!
+        env
+        "string-length"
+        (scm-unary
+          "string-length"
+          (fn (s) (string-length (scheme-string-value s)))))
+      (scheme-env-bind!
+        env
+        "string=?"
+        (scm-binary
+          "string=?"
+          (fn (a b) (= (scheme-string-value a) (scheme-string-value b)))))
+      (scheme-env-bind!
+        env
+        "string-append"
+        (fn
+          (args)
+          (scheme-string-make
+            (scm-fold-step
+              (fn (acc s) (str acc (scheme-string-value s)))
+              ""
+              args))))
+      (scheme-env-bind!
+        env
+        "substring"
+        (fn
+          (args)
+          (cond
+            ((not (= (length args) 3))
+              (error "substring: expects (str start end)"))
+            (:else
+              (scheme-string-make
+                (substring
+                  (scheme-string-value (first args))
+                  (nth args 1)
+                  (nth args 2)))))))
+      (scheme-env-bind!
+        env
+        "char=?"
+        (scm-binary
+          "char=?"
+          (fn (a b) (= (scheme-char-value a) (scheme-char-value b)))))
+      (scheme-env-bind! env "vector" (fn (args) (scheme-vector-make args)))
+      (scheme-env-bind!
+        env
+        "vector-length"
+        (scm-unary
+          "vector-length"
+          (fn (v) (length (scheme-vector-elements v)))))
+      (scheme-env-bind!
+        env
+        "vector-ref"
+        (scm-binary
+          "vector-ref"
+          (fn (v i) (nth (scheme-vector-elements v) i))))
+      (scheme-env-bind!
+        env
+        "vector->list"
+        (scm-unary "vector->list" (fn (v) (scheme-vector-elements v))))
+      (scheme-env-bind!
+        env
+        "list->vector"
+        (scm-unary "list->vector" (fn (xs) (scheme-vector-make xs))))
+      (scheme-env-bind!
+        env
+        "make-vector"
+        (fn
+          (args)
+          (cond
+            ((= (length args) 1)
+              (scheme-vector-make
+                (scm-make-vector-step (first args) nil (list))))
+            ((= (length args) 2)
+              (scheme-vector-make
+                (scm-make-vector-step
+                  (first args)
+                  (nth args 1)
+                  (list))))
+            (:else (error "make-vector: expects (n [fill])")))))
+      (scheme-env-bind! env "eqv?" (scm-binary "eqv?" (fn (a b) (= a b))))
+      (scheme-env-bind!
+        env
+        "equal?"
+        (scm-binary "equal?" (fn (a b) (= a b))))
+      (scheme-env-bind! env "eq?" (scm-binary "eq?" (fn (a b) (= a b))))
+      env)))

lib/scheme/tests/eval.sx

@@ -0,0 +1,162 @@
+;; lib/scheme/tests/eval.sx — exercises lib/scheme/eval.sx (Phase 2).
+
+(define scm-eval-pass 0)
+(define scm-eval-fail 0)
+(define scm-eval-fails (list))
+
+(define
+  scm-eval-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! scm-eval-pass (+ scm-eval-pass 1))
+      (begin
+        (set! scm-eval-fail (+ scm-eval-fail 1))
+        (append! scm-eval-fails {:name name :actual actual :expected expected})))))
+
+(define scm-eval-src (fn (src env) (scheme-eval (scheme-parse src) env)))
+
+;; A toy env with arithmetic + list primitives.
+(define
+  scm-test-env
+  (fn
+    ()
+    (let
+      ((env (scheme-make-env)))
+      (scheme-env-bind!
+        env
+        "+"
+        (fn (args) (+ (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "-"
+        (fn (args) (- (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "*"
+        (fn (args) (* (first args) (nth args 1))))
+      (scheme-env-bind! env "list" (fn (args) args))
+      env)))
+
+;; ── self-evaluating ──────────────────────────────────────────────
+(scm-eval-test
+  "lit: integer"
+  (scm-eval-src "42" (scheme-make-env))
+  42)
+(scm-eval-test "lit: float" (scm-eval-src "3.14" (scheme-make-env)) 3.14)
+(scm-eval-test "lit: #t" (scm-eval-src "#t" (scheme-make-env)) true)
+(scm-eval-test "lit: #f" (scm-eval-src "#f" (scheme-make-env)) false)
+(scm-eval-test
+  "lit: empty list"
+  (scm-eval-src "()" (scheme-make-env))
+  (list))
+(scm-eval-test
+  "lit: string"
+  (scheme-string? (scm-eval-src "\"hello\"" (scheme-make-env)))
+  true)
+(scm-eval-test
+  "lit: char"
+  (scheme-char? (scm-eval-src "#\\a" (scheme-make-env)))
+  true)
+(scm-eval-test
+  "lit: vector"
+  (scheme-vector? (scm-eval-src "#(1 2 3)" (scheme-make-env)))
+  true)
+
+;; ── symbol lookup ────────────────────────────────────────────────
+(scm-eval-test
+  "sym: bound"
+  (let
+    ((env (scheme-make-env)))
+    (scheme-env-bind! env "x" 100)
+    (scm-eval-src "x" env))
+  100)
+(scm-eval-test
+  "sym: parent chain"
+  (let
+    ((p (scheme-make-env)))
+    (scheme-env-bind! p "outer" 1)
+    (let
+      ((c (scheme-extend-env p)))
+      (scheme-env-bind! c "inner" 2)
+      (+ (scm-eval-src "outer" c) (scm-eval-src "inner" c))))
+  3)
+(scm-eval-test
+  "sym: shadowing"
+  (let
+    ((p (scheme-make-env)))
+    (scheme-env-bind! p "x" 1)
+    (let
+      ((c (scheme-extend-env p)))
+      (scheme-env-bind! c "x" 2)
+      (scm-eval-src "x" c)))
+  2)
+
+;; ── quote ────────────────────────────────────────────────────────
+(scm-eval-test
+  "quote: symbol"
+  (scm-eval-src "(quote foo)" (scheme-make-env))
+  "foo")
+(scm-eval-test
+  "quote: list"
+  (scm-eval-src "(quote (+ 1 2))" (scheme-make-env))
+  (list "+" 1 2))
+(scm-eval-test "quote: sugar 'x" (scm-eval-src "'x" (scheme-make-env)) "x")
+(scm-eval-test
+  "quote: sugar list"
+  (scm-eval-src "'(a b c)" (scheme-make-env))
+  (list "a" "b" "c"))
+(scm-eval-test
+  "quote: nested"
+  (scm-eval-src "''x" (scheme-make-env))
+  (list "quote" "x"))
+
+;; ── primitive application ────────────────────────────────────────
+(scm-eval-test "prim: +" (scm-eval-src "(+ 2 3)" (scm-test-env)) 5)
+(scm-eval-test
+  "prim: nested +"
+  (scm-eval-src "(+ (+ 1 2) (+ 3 4))" (scm-test-env))
+  10)
+(scm-eval-test
+  "prim: mixed ops"
+  (scm-eval-src "(- (* 4 5) (+ 3 2))" (scm-test-env))
+  15)
+(scm-eval-test
+  "prim: list builds SX list"
+  (scm-eval-src "(list 1 2 3)" (scm-test-env))
+  (list 1 2 3))
+(scm-eval-test
+  "prim: args eval in order"
+  (let
+    ((env (scm-test-env)))
+    (scheme-env-bind! env "a" 10)
+    (scheme-env-bind! env "b" 20)
+    (scm-eval-src "(+ a b)" env))
+  30)
+
+;; ── env-as-value (the third-consumer demonstration) ─────────────
+;; Scheme's env IS lib/guest/reflective/env.sx's canonical wire shape
+;; with no adapter cfg. Verify the kit primitives work directly.
+(scm-eval-test
+  "env: refl-env? on Scheme env"
+  (refl-env? (scheme-make-env))
+  true)
+(scm-eval-test
+  "env: lookup via kit"
+  (let
+    ((env (scheme-make-env)))
+    (refl-env-bind! env "name" "scheme")
+    (refl-env-lookup env "name"))
+  "scheme")
+(scm-eval-test
+  "env: find-frame walks parent"
+  (let
+    ((p (scheme-make-env)))
+    (refl-env-bind! p "root-binding" 99)
+    (let
+      ((c (scheme-extend-env p)))
+      (= (refl-env-find-frame c "root-binding") p)))
+  true)
+
+(define scm-eval-tests-run! (fn () {:total (+ scm-eval-pass scm-eval-fail) :passed scm-eval-pass :failed scm-eval-fail :fails scm-eval-fails}))

lib/scheme/tests/parse.sx

@@ -0,0 +1,177 @@
+;; lib/scheme/tests/parse.sx — exercises lib/scheme/parser.sx.
+
+(define scm-test-pass 0)
+(define scm-test-fail 0)
+(define scm-test-fails (list))
+
+(define
+  scm-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! scm-test-pass (+ scm-test-pass 1))
+      (begin
+        (set! scm-test-fail (+ scm-test-fail 1))
+        (append! scm-test-fails {:name name :actual actual :expected expected})))))
+
+;; ── numbers ───────────────────────────────────────────────────────
+(scm-test "num: integer" (scheme-parse "42") 42)
+(scm-test "num: zero" (scheme-parse "0") 0)
+(scm-test "num: negative" (scheme-parse "-17") -17)
+(scm-test "num: float" (scheme-parse "3.14") 3.14)
+(scm-test "num: exponent" (scheme-parse "1e3") 1000)
+(scm-test "num: negative float" (scheme-parse "-2.5") -2.5)
+
+;; ── booleans ──────────────────────────────────────────────────────
+(scm-test "bool: #t" (scheme-parse "#t") true)
+(scm-test "bool: #true" (scheme-parse "#true") true)
+(scm-test "bool: #f" (scheme-parse "#f") false)
+(scm-test "bool: #false" (scheme-parse "#false") false)
+
+;; ── strings ───────────────────────────────────────────────────────
+(scm-test "str: empty" (scheme-string-value (scheme-parse "\"\"")) "")
+(scm-test
+  "str: hello"
+  (scheme-string-value (scheme-parse "\"hello\""))
+  "hello")
+(scm-test "str: predicate" (scheme-string? (scheme-parse "\"x\"")) true)
+(scm-test "str: not symbol" (scheme-string? (scheme-parse "x")) false)
+(scm-test
+  "str: escape newline"
+  (scheme-string-value (scheme-parse "\"a\\nb\""))
+  "a\nb")
+(scm-test
+  "str: escape tab"
+  (scheme-string-value (scheme-parse "\"a\\tb\""))
+  "a\tb")
+(scm-test
+  "str: escape quote"
+  (scheme-string-value (scheme-parse "\"a\\\"b\""))
+  "a\"b")
+
+;; ── symbols ───────────────────────────────────────────────────────
+(scm-test "sym: word" (scheme-parse "foo") "foo")
+(scm-test "sym: hyphenated" (scheme-parse "set-car!") "set-car!")
+(scm-test "sym: question mark" (scheme-parse "null?") "null?")
+(scm-test "sym: arrow" (scheme-parse "->") "->")
+(scm-test "sym: lt-eq" (scheme-parse "<=") "<=")
+(scm-test "sym: bare plus" (scheme-parse "+") "+")
+(scm-test "sym: bare minus" (scheme-parse "-") "-")
+(scm-test "sym: dot-prefixed" (scheme-parse ".foo") ".foo")
+
+;; ── characters ────────────────────────────────────────────────────
+(scm-test "char: single" (scheme-char-value (scheme-parse "#\\a")) "a")
+(scm-test "char: space" (scheme-char-value (scheme-parse "#\\space")) " ")
+(scm-test "char: newline" (scheme-char-value (scheme-parse "#\\newline")) "\n")
+(scm-test "char: tab" (scheme-char-value (scheme-parse "#\\tab")) "\t")
+(scm-test "char: predicate" (scheme-char? (scheme-parse "#\\x")) true)
+(scm-test "char: digit" (scheme-char-value (scheme-parse "#\\5")) "5")
+
+;; ── vectors ───────────────────────────────────────────────────────
+(scm-test "vec: empty" (scheme-vector-elements (scheme-parse "#()")) (list))
+(scm-test
+  "vec: numbers"
+  (scheme-vector-elements (scheme-parse "#(1 2 3)"))
+  (list 1 2 3))
+(scm-test "vec: predicate" (scheme-vector? (scheme-parse "#(1)")) true)
+(scm-test "vec: not list" (scheme-vector? (scheme-parse "(1)")) false)
+;; Nested vector: SX `=` doesn't deep-compare dicts-with-list-values
+;; reliably under this CEK path, so check structure piecewise.
+(scm-test "vec: nested first"
+  (first (scheme-vector-elements (scheme-parse "#(a #(b c) d)"))) "a")
+(scm-test "vec: nested second is vector"
+  (scheme-vector?
+    (nth (scheme-vector-elements (scheme-parse "#(a #(b c) d)")) 1))
+  true)
+(scm-test "vec: nested second elements"
+  (scheme-vector-elements
+    (nth (scheme-vector-elements (scheme-parse "#(a #(b c) d)")) 1))
+  (list "b" "c"))
+
+;; ── lists ─────────────────────────────────────────────────────────
+(scm-test "list: empty" (scheme-parse "()") (list))
+(scm-test "list: flat" (scheme-parse "(a b c)") (list "a" "b" "c"))
+(scm-test
+  "list: nested"
+  (scheme-parse "(a (b c) d)")
+  (list "a" (list "b" "c") "d"))
+(scm-test
+  "list: mixed atoms"
+  (scheme-parse "(1 #t foo)")
+  (list 1 true "foo"))
+
+;; ── reader macros ─────────────────────────────────────────────────
+(scm-test "quote: 'foo" (scheme-parse "'foo") (list "quote" "foo"))
+(scm-test
+  "quote: '(a b c)"
+  (scheme-parse "'(a b c)")
+  (list "quote" (list "a" "b" "c")))
+(scm-test "quasiquote: `x" (scheme-parse "`x") (list "quasiquote" "x"))
+(scm-test "unquote: ,x" (scheme-parse ",x") (list "unquote" "x"))
+(scm-test
+  "unquote-splicing: ,@x"
+  (scheme-parse ",@x")
+  (list "unquote-splicing" "x"))
+(scm-test
+  "qq mix"
+  (scheme-parse "`(a ,b ,@c)")
+  (list
+    "quasiquote"
+    (list "a" (list "unquote" "b") (list "unquote-splicing" "c"))))
+
+;; ── comments ──────────────────────────────────────────────────────
+(scm-test "comment: line" (scheme-parse "; nope\n42") 42)
+(scm-test "comment: trailing" (scheme-parse "42 ; tail") 42)
+(scm-test
+  "comment: inside list"
+  (scheme-parse "(a ; mid\n  b)")
+  (list "a" "b"))
+(scm-test "comment: block simple" (scheme-parse "#| skip |# 42") 42)
+(scm-test
+  "comment: block nested"
+  (scheme-parse "#| outer #| inner |# done |# 42")
+  42)
+(scm-test "comment: datum #;" (scheme-parse "#;skipme 42") 42)
+(scm-test
+  "comment: datum skips list"
+  (scheme-parse "#;(1 2 3) 42")
+  42)
+
+;; ── parse-all ─────────────────────────────────────────────────────
+(scm-test "all: empty" (scheme-parse-all "") (list))
+(scm-test
+  "all: three forms"
+  (scheme-parse-all "1 2 3")
+  (list 1 2 3))
+(scm-test
+  "all: mixed"
+  (scheme-parse-all "(if #t 1 2) foo")
+  (list (list "if" true 1 2) "foo"))
+
+;; ── classic Scheme idioms ─────────────────────────────────────────
+(scm-test
+  "classic: lambda"
+  (scheme-parse "(lambda (x) (+ x 1))")
+  (list "lambda" (list "x") (list "+" "x" 1)))
+(scm-test
+  "classic: define"
+  (scheme-parse "(define (sq x) (* x x))")
+  (list "define" (list "sq" "x") (list "*" "x" "x")))
+(scm-test
+  "classic: let"
+  (scheme-parse "(let ((x 1) (y 2)) (+ x y))")
+  (list
+    "let"
+    (list (list "x" 1) (list "y" 2))
+    (list "+" "x" "y")))
+(scm-test
+  "classic: if"
+  (scheme-parse "(if (zero? n) 1 (* n (fact (- n 1))))")
+  (list
+    "if"
+    (list "zero?" "n")
+    1
+    (list "*" "n" (list "fact" (list "-" "n" 1)))))
+
+(define scm-tests-run! (fn () {:total (+ scm-test-pass scm-test-fail) :passed scm-test-pass :failed scm-test-fail :fails scm-test-fails}))

lib/scheme/tests/runtime.sx

@@ -0,0 +1,213 @@
+;; lib/scheme/tests/runtime.sx — exercises the standard env.
+
+(define scm-rt-pass 0)
+(define scm-rt-fail 0)
+(define scm-rt-fails (list))
+
+(define
+  scm-rt-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! scm-rt-pass (+ scm-rt-pass 1))
+      (begin
+        (set! scm-rt-fail (+ scm-rt-fail 1))
+        (append! scm-rt-fails {:name name :actual actual :expected expected})))))
+
+(define
+  scm-rt
+  (fn (src) (scheme-eval (scheme-parse src) (scheme-standard-env))))
+
+(define
+  scm-rt-all
+  (fn
+    (src)
+    (scheme-eval-program (scheme-parse-all src) (scheme-standard-env))))
+
+;; ── Variadic arithmetic ─────────────────────────────────────────
+(scm-rt-test "+: zero" (scm-rt "(+)") 0)
+(scm-rt-test "+: one" (scm-rt "(+ 7)") 7)
+(scm-rt-test "+: many" (scm-rt "(+ 1 2 3 4 5)") 15)
+(scm-rt-test "-: one" (scm-rt "(- 10)") -10)
+(scm-rt-test "-: many" (scm-rt "(- 100 1 2 3)") 94)
+(scm-rt-test "*: zero" (scm-rt "(*)") 1)
+(scm-rt-test "*: many" (scm-rt "(* 1 2 3 4)") 24)
+(scm-rt-test "/: two" (scm-rt "(/ 20 5)") 4)
+
+;; ── Chained comparison ──────────────────────────────────────────
+(scm-rt-test "<: chained" (scm-rt "(< 1 2 3 4 5)") true)
+(scm-rt-test "<: not strict" (scm-rt "(< 1 2 2 3)") false)
+(scm-rt-test ">: chained" (scm-rt "(> 5 4 3 2 1)") true)
+(scm-rt-test "<=: with equality" (scm-rt "(<= 1 1 2 3 3)") true)
+(scm-rt-test "=: chained" (scm-rt "(= 7 7 7)") true)
+
+;; ── Numerical ───────────────────────────────────────────────────
+(scm-rt-test "abs neg" (scm-rt "(abs -5)") 5)
+(scm-rt-test "abs pos" (scm-rt "(abs 5)") 5)
+(scm-rt-test "min" (scm-rt "(min 3 1 4 1 5)") 1)
+(scm-rt-test "max" (scm-rt "(max 3 1 4 1 5)") 5)
+(scm-rt-test "modulo" (scm-rt "(modulo 10 3)") 1)
+(scm-rt-test "zero? 0" (scm-rt "(zero? 0)") true)
+(scm-rt-test "zero? 1" (scm-rt "(zero? 1)") false)
+(scm-rt-test "positive?" (scm-rt "(positive? 5)") true)
+(scm-rt-test "negative?" (scm-rt "(negative? -5)") true)
+
+;; ── Type predicates ─────────────────────────────────────────────
+(scm-rt-test "number? int" (scm-rt "(number? 42)") true)
+(scm-rt-test "number? str" (scm-rt "(number? \"hi\")") false)
+(scm-rt-test "boolean? #t" (scm-rt "(boolean? #t)") true)
+(scm-rt-test "boolean? 0" (scm-rt "(boolean? 0)") false)
+(scm-rt-test "string? str" (scm-rt "(string? \"hi\")") true)
+(scm-rt-test "string? sym" (scm-rt "(string? 'foo)") false)
+(scm-rt-test "symbol? sym" (scm-rt "(symbol? 'foo)") true)
+(scm-rt-test "null? ()" (scm-rt "(null? '())") true)
+(scm-rt-test "null? (1)" (scm-rt "(null? '(1))") false)
+(scm-rt-test "pair? (1)" (scm-rt "(pair? '(1))") true)
+(scm-rt-test "pair? ()" (scm-rt "(pair? '())") false)
+(scm-rt-test "procedure? lambda" (scm-rt "(procedure? (lambda (x) x))") true)
+(scm-rt-test "procedure? +" (scm-rt "(procedure? +)") true)
+(scm-rt-test "procedure? 42" (scm-rt "(procedure? 42)") false)
+(scm-rt-test "not #t" (scm-rt "(not #t)") false)
+(scm-rt-test "not #f" (scm-rt "(not #f)") true)
+(scm-rt-test "not 0" (scm-rt "(not 0)") false)
+
+;; ── List operations ─────────────────────────────────────────────
+(scm-rt-test
+  "cons"
+  (scm-rt "(cons 1 '(2 3))")
+  (list 1 2 3))
+(scm-rt-test "car" (scm-rt "(car '(1 2 3))") 1)
+(scm-rt-test "cdr" (scm-rt "(cdr '(1 2 3))") (list 2 3))
+(scm-rt-test
+  "list builds"
+  (scm-rt "(list 1 2 3)")
+  (list 1 2 3))
+(scm-rt-test "list empty" (scm-rt "(list)") (list))
+(scm-rt-test "length 3" (scm-rt "(length '(a b c))") 3)
+(scm-rt-test "length 0" (scm-rt "(length '())") 0)
+(scm-rt-test
+  "reverse"
+  (scm-rt "(reverse '(1 2 3))")
+  (list 3 2 1))
+(scm-rt-test "reverse empty" (scm-rt "(reverse '())") (list))
+(scm-rt-test
+  "append two"
+  (scm-rt "(append '(1 2) '(3 4))")
+  (list 1 2 3 4))
+(scm-rt-test
+  "append three"
+  (scm-rt "(append '(1) '(2) '(3))")
+  (list 1 2 3))
+(scm-rt-test "append empty" (scm-rt "(append)") (list))
+
+;; ── Higher-order combinators ────────────────────────────────────
+(scm-rt-test
+  "map square"
+  (scm-rt "(map (lambda (x) (* x x)) '(1 2 3 4))")
+  (list 1 4 9 16))
+(scm-rt-test
+  "map with primitive"
+  (scm-rt-all "(define inc (lambda (x) (+ x 1))) (map inc '(10 20 30))")
+  (list 11 21 31))
+(scm-rt-test
+  "filter positives"
+  (scm-rt "(filter positive? '(-2 -1 0 1 2))")
+  (list 1 2))
+(scm-rt-test
+  "filter empty result"
+  (scm-rt "(filter (lambda (x) #f) '(1 2 3))")
+  (list))
+(scm-rt-test
+  "fold-left sum"
+  (scm-rt "(fold-left + 0 '(1 2 3 4 5))")
+  15)
+(scm-rt-test
+  "fold-left build list"
+  (scm-rt "(fold-left (lambda (acc x) (cons x acc)) '() '(1 2 3))")
+  (list 3 2 1))
+(scm-rt-test
+  "fold-right preserves order"
+  (scm-rt "(fold-right cons '() '(1 2 3))")
+  (list 1 2 3))
+(scm-rt-test
+  "for-each side effect"
+  (let
+    ((env (scheme-standard-env)))
+    (scheme-eval-program
+      (scheme-parse-all
+        "(define sum 0) (for-each (lambda (n) (set! sum (+ sum n))) '(1 2 3 4 5)) sum")
+      env))
+  15)
+
+;; ── apply ───────────────────────────────────────────────────────
+(scm-rt-test "apply +" (scm-rt "(apply + '(1 2 3 4 5))") 15)
+(scm-rt-test
+  "apply lambda"
+  (scm-rt "(apply (lambda (a b c) (+ a (* b c))) '(1 2 3))")
+  7)
+(scm-rt-test
+  "apply via map"
+  (scm-rt "(apply + (map (lambda (x) (* x x)) '(1 2 3)))")
+  14)
+
+;; ── String / char / vector ──────────────────────────────────────
+(scm-rt-test "string-length" (scm-rt "(string-length \"hello\")") 5)
+(scm-rt-test "string=? same" (scm-rt "(string=? \"abc\" \"abc\")") true)
+(scm-rt-test "string=? diff" (scm-rt "(string=? \"abc\" \"abd\")") false)
+(scm-rt-test
+  "string-append"
+  (scheme-string-value (scm-rt "(string-append \"hello\" \" \" \"world\")"))
+  "hello world")
+(scm-rt-test "vector?" (scm-rt "(vector? #(1 2 3))") true)
+(scm-rt-test "vector-length" (scm-rt "(vector-length #(1 2 3))") 3)
+(scm-rt-test "vector-ref" (scm-rt "(vector-ref #(10 20 30) 1)") 20)
+(scm-rt-test
+  "vector->list"
+  (scm-rt "(vector->list #(1 2 3))")
+  (list 1 2 3))
+
+;; ── Classic Scheme programs ─────────────────────────────────────
+(scm-rt-test
+  "factorial 5"
+  (scm-rt-all
+    "(define (fact n) (if (<= n 1) 1 (* n (fact (- n 1))))) (fact 5)")
+  120)
+(scm-rt-test
+  "factorial 10"
+  (scm-rt-all
+    "(define (fact n) (if (<= n 1) 1 (* n (fact (- n 1))))) (fact 10)")
+  3628800)
+(scm-rt-test
+  "fib 10"
+  (scm-rt-all
+    "(define (fib n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2))))) (fib 10)")
+  55)
+(scm-rt-test
+  "sum via reduce"
+  (scm-rt "(fold-left + 0 (map (lambda (x) (* x x)) '(1 2 3 4 5)))")
+  55)
+(scm-rt-test
+  "length via reduce"
+  (scm-rt-all
+    "(define (len xs) (fold-left (lambda (acc _) (+ acc 1)) 0 xs)) (len '(a b c d))")
+  4)
+(scm-rt-test
+  "Y-ish reverse"
+  (scm-rt-all
+    "(define (rev xs) (if (null? xs) '() (append (rev (cdr xs)) (list (car xs))))) (rev '(1 2 3 4))")
+  (list 4 3 2 1))
+
+;; ── env-as-value (kit consumer demo) ────────────────────────────
+(scm-rt-test
+  "env: standard-env is refl-env"
+  (refl-env? (scheme-standard-env))
+  true)
+(scm-rt-test
+  "env: kit lookup finds primitive"
+  (let
+    ((env (scheme-standard-env)))
+    (callable? (refl-env-lookup env "+")))
+  true)
+
+(define scm-rt-tests-run! (fn () {:total (+ scm-rt-pass scm-rt-fail) :passed scm-rt-pass :failed scm-rt-fail :fails scm-rt-fails}))

lib/scheme/tests/syntax.sx

@@ -0,0 +1,288 @@
+;; lib/scheme/tests/syntax.sx — exercises Phase 3 syntactic operators.
+
+(define scm-syn-pass 0)
+(define scm-syn-fail 0)
+(define scm-syn-fails (list))
+
+(define
+  scm-syn-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! scm-syn-pass (+ scm-syn-pass 1))
+      (begin
+        (set! scm-syn-fail (+ scm-syn-fail 1))
+        (append! scm-syn-fails {:name name :actual actual :expected expected})))))
+
+(define scm-syn-eval (fn (src env) (scheme-eval (scheme-parse src) env)))
+
+(define
+  scm-syn-eval-all
+  (fn (src env) (scheme-eval-program (scheme-parse-all src) env)))
+
+;; Test env with arithmetic primitives.
+(define
+  scm-syn-env
+  (fn
+    ()
+    (let
+      ((env (scheme-make-env)))
+      (scheme-env-bind!
+        env
+        "+"
+        (fn (args) (+ (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "-"
+        (fn (args) (- (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "*"
+        (fn (args) (* (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "/"
+        (fn (args) (/ (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "<="
+        (fn (args) (<= (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "<"
+        (fn (args) (< (first args) (nth args 1))))
+      (scheme-env-bind!
+        env
+        "="
+        (fn (args) (= (first args) (nth args 1))))
+      (scheme-env-bind! env "list" (fn (args) args))
+      (scheme-env-bind!
+        env
+        "cons"
+        (fn (args) (cons (first args) (nth args 1))))
+      (scheme-env-bind! env "car" (fn (args) (first (first args))))
+      (scheme-env-bind! env "cdr" (fn (args) (rest (first args))))
+      env)))
+
+;; ── if ───────────────────────────────────────────────────────────
+(scm-syn-test
+  "if: true"
+  (scm-syn-eval "(if #t 1 2)" (scm-syn-env))
+  1)
+(scm-syn-test
+  "if: false"
+  (scm-syn-eval "(if #f 1 2)" (scm-syn-env))
+  2)
+(scm-syn-test
+  "if: predicate"
+  (scm-syn-eval "(if (<= 1 2) 99 nope)" (scm-syn-env))
+  99)
+(scm-syn-test
+  "if: no else returns nil"
+  (scm-syn-eval "(if #f 99)" (scm-syn-env))
+  nil)
+(scm-syn-test
+  "if: truthy non-#f"
+  (scm-syn-eval "(if 0 'yes 'no)" (scm-syn-env))
+  "yes")
+
+;; ── define ───────────────────────────────────────────────────────
+(scm-syn-test
+  "define: bind value"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval "(define x 42)" env)
+    (scm-syn-eval "x" env))
+  42)
+(scm-syn-test
+  "define: function sugar"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define (double n) (+ n n)) (double 21)" env))
+  42)
+(scm-syn-test
+  "define: redefine"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define x 1) (define x 2) x" env))
+  2)
+
+;; ── set! ─────────────────────────────────────────────────────────
+(scm-syn-test
+  "set!: mutate"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define x 1) (set! x 99) x" env))
+  99)
+(scm-syn-test
+  "set!: walks parent"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define x 1) ((lambda () (set! x 100))) x" env))
+  100)
+(scm-syn-test
+  "set!: errors on unbound"
+  (guard
+    (e (true :raised))
+    (scm-syn-eval-all "(set! never-defined 1)" (scm-syn-env)))
+  :raised)
+
+;; ── begin ────────────────────────────────────────────────────────
+(scm-syn-test
+  "begin: empty returns nil"
+  (scm-syn-eval "(begin)" (scm-syn-env))
+  nil)
+(scm-syn-test
+  "begin: returns last"
+  (scm-syn-eval "(begin 1 2 3)" (scm-syn-env))
+  3)
+(scm-syn-test
+  "begin: side effects in order"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define x 0) (begin (set! x 1) (set! x 2) (set! x 3)) x"
+      env))
+  3)
+
+;; ── lambda ───────────────────────────────────────────────────────
+(scm-syn-test
+  "lambda: identity"
+  (scm-syn-eval "((lambda (x) x) 42)" (scm-syn-env))
+  42)
+(scm-syn-test
+  "lambda: arithmetic"
+  (scm-syn-eval "((lambda (x y) (+ x y)) 3 4)" (scm-syn-env))
+  7)
+(scm-syn-test
+  "lambda: zero args"
+  (scm-syn-eval "((lambda () 99))" (scm-syn-env))
+  99)
+(scm-syn-test
+  "lambda: multi-body"
+  (scm-syn-eval "((lambda (x) (define t (+ x 1)) (+ t t)) 5)" (scm-syn-env))
+  12)
+(scm-syn-test
+  "lambda: rest-arg as bare symbol"
+  (scm-syn-eval "((lambda args args) 1 2 3)" (scm-syn-env))
+  (list 1 2 3))
+
+;; ── closures ─────────────────────────────────────────────────────
+(scm-syn-test
+  "closure: captures binding"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define (make-adder n) (lambda (x) (+ x n))) ((make-adder 10) 5)"
+      env))
+  15)
+(scm-syn-test
+  "closure: counter via set!"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define (make-counter) (define n 0) (lambda () (set! n (+ n 1)) n)) (define c (make-counter)) (c) (c) (c)"
+      env))
+  3)
+(scm-syn-test
+  "closure: curried"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define curry+ (lambda (a) (lambda (b) (lambda (c) (+ a (+ b c)))))) (((curry+ 1) 2) 3)"
+      env))
+  6)
+
+;; ── recursion ────────────────────────────────────────────────────
+(scm-syn-test
+  "recursive: factorial 5"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define (fact n) (if (<= n 1) 1 (* n (fact (- n 1))))) (fact 5)"
+      env))
+  120)
+(scm-syn-test
+  "recursive: factorial 10"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define (fact n) (if (<= n 1) 1 (* n (fact (- n 1))))) (fact 10)"
+      env))
+  3628800)
+(scm-syn-test
+  "recursive: list length"
+  (let
+    ((env (scm-syn-env)))
+    (scm-syn-eval-all
+      "(define (len xs) (if (= 0 (- 0 0)) (if (= xs (quote ())) 0 (+ 1 (len (cdr xs)))) 0)) (len '(a b c d))"
+      env))
+  4)
+
+;; ── quote vs eval distinction ────────────────────────────────────
+(scm-syn-test
+  "quote: list literal"
+  (scm-syn-eval "'(1 2 3)" (scm-syn-env))
+  (list 1 2 3))
+(scm-syn-test
+  "quote: nested"
+  (scm-syn-eval "'(a (b c) d)" (scm-syn-env))
+  (list "a" (list "b" "c") "d"))
+(scm-syn-test
+  "quote: symbol vs evaluated"
+  (let ((env (scm-syn-env))) (scm-syn-eval-all "(define x 42) 'x" env))
+  "x")
+
+;; ── let / let* ───────────────────────────────────────────────────
+(scm-syn-test "let: returns body"
+  (scm-syn-eval "(let ((x 5)) (+ x 1))" (scm-syn-env)) 6)
+(scm-syn-test "let: multiple bindings"
+  (scm-syn-eval "(let ((x 3) (y 4)) (+ x y))" (scm-syn-env)) 7)
+(scm-syn-test "let: parallel (RHS sees outer)"
+  (let ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define x 1) (let ((x 10) (y x)) y)" env)) 1)
+(scm-syn-test "let: bindings don't leak"
+  (let ((env (scm-syn-env)))
+    (scm-syn-eval-all "(define x 1) (let ((x 99)) x) x" env)) 1)
+(scm-syn-test "let*: sequential"
+  (scm-syn-eval "(let* ((x 1) (y (+ x 1)) (z (+ y 1))) z)"
+                (scm-syn-env)) 3)
+(scm-syn-test "let*: shadow earlier"
+  (scm-syn-eval "(let* ((x 1) (x 2)) x)" (scm-syn-env)) 2)
+
+;; ── cond / when / unless ─────────────────────────────────────────
+(scm-syn-test "cond: first match"
+  (scm-syn-eval "(cond (#f 1) (#t 2) (#t 3))" (scm-syn-env)) 2)
+(scm-syn-test "cond: else"
+  (scm-syn-eval "(cond (#f 1) (else 99))" (scm-syn-env)) 99)
+(scm-syn-test "cond: untaken not evaluated"
+  (scm-syn-eval "(cond (#t 7) (nope ignored))" (scm-syn-env)) 7)
+(scm-syn-test "cond: no match returns nil"
+  (scm-syn-eval "(cond (#f 1) (#f 2))" (scm-syn-env)) nil)
+(scm-syn-test "cond: test-only clause"
+  (scm-syn-eval "(cond (42))" (scm-syn-env)) 42)
+(scm-syn-test "when: true"
+  (scm-syn-eval "(when #t 1 2 3)" (scm-syn-env)) 3)
+(scm-syn-test "when: false"
+  (scm-syn-eval "(when #f nope)" (scm-syn-env)) nil)
+(scm-syn-test "unless: false"
+  (scm-syn-eval "(unless #f 42)" (scm-syn-env)) 42)
+(scm-syn-test "unless: true"
+  (scm-syn-eval "(unless #t nope)" (scm-syn-env)) nil)
+
+;; ── and / or ─────────────────────────────────────────────────────
+(scm-syn-test "and: empty"
+  (scm-syn-eval "(and)" (scm-syn-env)) true)
+(scm-syn-test "and: all truthy returns last"
+  (scm-syn-eval "(and 1 2 3)" (scm-syn-env)) 3)
+(scm-syn-test "and: short-circuit on #f"
+  (scm-syn-eval "(and 1 #f nope)" (scm-syn-env)) false)
+(scm-syn-test "or: empty"
+  (scm-syn-eval "(or)" (scm-syn-env)) false)
+(scm-syn-test "or: first truthy"
+  (scm-syn-eval "(or #f 42 nope)" (scm-syn-env)) 42)
+(scm-syn-test "or: all #f"
+  (scm-syn-eval "(or #f #f #f)" (scm-syn-env)) false)
+
+(define scm-syn-tests-run! (fn () {:total (+ scm-syn-pass scm-syn-fail) :passed scm-syn-pass :failed scm-syn-fail :fails scm-syn-fails}))

plans/scheme-on-sx.md

@@ -0,0 +1,150 @@
+# Scheme-on-SX: the reflective-kit second-consumer port
+
+The kernel-on-sx loop documented six reflective API candidates; two are now live (`env.sx`, `class-chain.sx`). Three more — `evaluator.sx`, `hygiene.sx`, `quoting.sx` — wait on a guest with operative-free lexical scope, hygienic syntax-transformer infrastructure, and quasiquote. **Scheme is exactly that guest.**
+
+A correct R7RS-small implementation acts as second consumer for those three kits in one stroke. It also confirms a third independent consumer for `env.sx` (after Kernel + Tcl + Smalltalk), and a candidate fourth consumer for `class-chain.sx` (Scheme's record types have parent fields — though OO is non-core in Scheme so the fit is weaker).
+
+## Strategic note on `combiner.sx`
+
+Scheme has *no fexprs*. `combiner.sx`'s applicative/operative split is Kernel-specific machinery. **Scheme is not a second consumer for `combiner.sx`** — that file stays Kernel-only until a Maru, Klisp, or CL-fexpr port arrives. The current session's earlier claim that Scheme "unlocks four more reflective kits" was over-counted; the correct number is **three**.
+
+## Scope decisions
+
+- **Target dialect:** R7RS-small. Source-only — no images, no FFI, no C extensions, no JIT.
+- **Numbers:** integers + floats. Rationals optional (defer to phase N+1). Complex out.
+- **Tail-call optimisation:** required. Implemented via the existing SX CEK machinery — call recursion in the evaluator uses iterative `cek-call` rather than host recursion.
+- **Continuations:** `call/cc` required for R7RS. Use SX's `call/cc` primitive directly.
+- **Hygienic macros:** `syntax-rules` required. `syntax-case` deferred.
+- **Char/string semantics:** Unicode codepoints; surface API matches R7RS section 6.
+- **I/O:** minimal stub (`display`, `write`, `newline`, `read`) on SX's IO surface.
+- **`define-library`:** required for module testing; implementation reuses SX's `define-library` if it's exposed, else hand-rolls a flat module registry.
+
+## Architecture sketch
+
+```
+lib/scheme/parser.sx     — reader: numbers, strings, symbols, booleans,
+                            chars #\c, vectors #(...), dotted-pairs (a . b),
+                            quasi-quote sugar, datum comments #;, block
+                            comments #| ... |#
+
+lib/scheme/eval.sx       — eval-expr ENV: walks AST. Symbols → env-lookup.
+                            Lists → look up head; if syntactic operator
+                            (if/lambda/define/set!/quote/quasiquote/
+                             let/let*/letrec/begin/cond/case/and/or/when/
+                             unless/do), dispatch to native handler. Else
+                            apply combiner (always applicative).
+
+                          ENV is `lib/guest/reflective/env.sx` directly
+                          — Scheme is the third consumer for env.sx with
+                          NO adapter cfg (canonical wire shape).
+
+lib/scheme/runtime.sx    — Standard environment, primitives, R7RS base.
+                            Variadic arithmetic, list ops, string ops,
+                            char ops, vector ops, define-record-type,
+                            syntax-rules, etc.
+
+lib/scheme/tests/        — Standard pattern: parse, eval, lambda+closure,
+                            macros (syntax-rules), call/cc, define-library,
+                            classic programs (factorial, Y, tree-walking,
+                            named let, do-loop), R7RS conformance subset.
+```
+
+## Roadmap
+
+### Phase 1 — Parser
+- [ ] Reader for R7RS lexical syntax: integers, floats, strings (with escapes), symbols (extended-identifier-character set), booleans `#t`/`#f`/`#true`/`#false`, characters `#\c` `#\space` `#\newline`, vectors `#(...)`, dotted pairs `(a . b)`, quote/quasiquote/unquote/unquote-splicing sugar (same reader macros as Kernel).
+- [ ] Datum comments `#;<datum>` (skip one whole expression).
+- [ ] Block comments `#| ... |#` (nestable).
+- [ ] Tests in `lib/scheme/tests/parse.sx`.
+
+### Phase 2 — Evaluator + env
+- [ ] `scheme-eval EXPR ENV` — primary entry, uses `lib/guest/reflective/env.sx` directly as the canonical scope chain. **Third consumer for env.sx.**
+- [ ] Self-evaluating: numbers, booleans, strings, chars, vectors.
+- [ ] Symbol lookup → `refl-env-lookup-with`.
+- [ ] List → look up head; syntactic operators dispatch natively; otherwise applicative call with evaluated args.
+- [ ] Tests in `lib/scheme/tests/eval.sx`.
+
+### Phase 3 — Syntactic operators
+- [ ] `if`, `quote`, `set!`, `define` (top-level + internal).
+- [ ] `lambda` — fixed-arity, rest-arg via dot, multi-body via implicit `begin`.
+- [ ] `let`, `let*`, `letrec`, `letrec*` — including named-let.
+- [ ] `begin` — implicit + explicit.
+- [ ] `cond`, `case`, `when`, `unless`, `and`, `or`, `do`.
+- [ ] Tests for each.
+
+### Phase 4 — Standard environment
+- [ ] Variadic `+ - * /` and chained comparison.
+- [ ] Type predicates (R7RS `number?`, `pair?`, `null?`, `symbol?`, `string?`, `procedure?`, `vector?`, `char?`, `boolean?`).
+- [ ] List ops: `cons car cdr caar cadr ... cddddr` (or just a subset), `list length reverse append map filter fold-left fold-right for-each`.
+- [ ] String ops: `string-length string-ref substring string-append string=? string<? char->integer integer->char`.
+- [ ] Char ops: `char->integer integer->char char-alphabetic? char-numeric?` etc.
+- [ ] Vector ops: `vector make-vector vector-length vector-ref vector-set! vector->list list->vector`.
+- [ ] I/O: `display write newline read`.
+- [ ] Numerical: `abs floor ceiling round truncate min max modulo quotient remainder gcd lcm expt`.
+- [ ] Classic programs: factorial, fib, list reversal, tree map.
+
+### Phase 5 — call/cc + dynamic-wind
+- [ ] `call-with-current-continuation` / `call/cc`.
+- [ ] `dynamic-wind`.
+- [ ] `with-exception-handler`, `raise`, `error`.
+- [ ] Tests: escape continuations, multi-shot via call/cc (chosen via host SX `call/cc`).
+
+### Phase 6 — `syntax-rules` + hygiene
+- [ ] `define-syntax`, `let-syntax`, `letrec-syntax`.
+- [ ] `syntax-rules` pattern matching, ellipsis, template instantiation.
+- [ ] Hygiene: scope-set / lifted-symbol implementation. **Second consumer for `lib/guest/reflective/hygiene.sx` extraction once that kit's API surface stabilises.**
+- [ ] Tests: hygienic identifier capture, ellipsis patterns, recursive macros.
+
+### Phase 7 — Reflection: `eval`, `interaction-environment`, etc.
+- [ ] `eval EXPR ENV` — applicative form of the evaluator. **Second consumer for `lib/guest/reflective/evaluator.sx` extraction.**
+- [ ] `interaction-environment`, `null-environment`, `scheme-report-environment`.
+- [ ] `environment?` predicate.
+
+### Phase 8 — `define-library` + module hygiene
+- [ ] `define-library`, `import`, `export`.
+- [ ] `cond-expand` for feature-flag conditionals.
+- [ ] Tests: cross-library imports, identifier renaming.
+
+### Phase 9 — Records
+- [ ] `define-record-type` with constructor/predicate/accessors/mutators.
+- [ ] Tests: typical record idioms.
+
+### Phase 10 — Quasiquote runtime
+- [ ] Backquote walker with depth tracking. **Second consumer for `lib/guest/reflective/quoting.sx` extraction.**
+- [ ] Tests including nested quasiquote.
+
+### Phase 11 — Conformance + scoreboard
+- [ ] Curated R7RS test slice (Chibi, Larceny, or hand-picked).
+- [ ] `lib/scheme/conformance.sh` + scoreboard.
+- [ ] Drive conformance toward 100% on chosen slice.
+
+## Reflective kit consumption — explicit mapping
+
+| Kit | When it lands | How Scheme uses it |
+|-----|--------------|-------------------|
+| `lib/guest/reflective/env.sx` | Phase 2 | Direct — canonical wire shape, no cfg needed. Third consumer. |
+| `lib/guest/reflective/evaluator.sx` | Phase 7 (will trigger the extraction) | Scheme's `eval`/`interaction-environment`/`null-environment` mirror the proposed `refl-eval`/`refl-make-environment`/`refl-current-env` triple. Second consumer → extraction unblocked. |
+| `lib/guest/reflective/hygiene.sx` | Phase 6 | Scheme's hygienic `syntax-rules` is the canonical implementation of scope sets / lifted symbols. Second consumer for the deferred Shutt-style hygiene work — Scheme's hygiene goes BEYOND Kernel's by-default-static-env-extension into proper scope-set lifting. Drives the deferred research-grade kit. |
+| `lib/guest/reflective/quoting.sx` | Phase 10 | Scheme's backquote walker is structurally identical to Kernel's `knl-quasi-walk`, with depth tracking added. Second consumer → extraction unblocked. |
+| `lib/guest/reflective/combiner.sx` | NEVER (no fexprs) | Not applicable. Stays Kernel-only until a fexpr-having consumer arrives. |
+| `lib/guest/reflective/short-circuit.sx` | Possibly Phase 3 | Scheme's `and`/`or` are syntactic, not operative; could be second consumer but adapter would need to bridge "macro that short-circuits" vs "operative that short-circuits". Marginal. |
+
+## Ground rules
+
+- **Scope:** only `lib/scheme/**` and `plans/scheme-on-sx.md` and `lib/guest/reflective/**` (for extraction work). Don't edit `spec/`, `hosts/`, `shared/`, or other `lib/<lang>/` directories.
+- **Consume:** `lib/guest/lex.sx` (character predicates), `lib/guest/reflective/env.sx` (scope chain), eventually `evaluator.sx`/`hygiene.sx`/`quoting.sx` once extracted with Scheme as second consumer.
+- **Commits:** one feature per commit. Short factual messages.
+- **Tests:** every phase ends with a test file. Conformance scoreboard at the end.
+- **Branch:** `loops/scheme`. Worktree pattern (already set up at `/root/rose-ash-loops/scheme`).
+- **Substrate gaps:** filed to `sx-improvements.md`, not fixed in this loop.
+
+## References
+
+- R7RS-small: https://small.r7rs.org/attachment/r7rs.pdf
+- Chibi Scheme — a small, readable R7RS implementation.
+- Dybvig, "Three Implementation Models for Scheme" — for the hygiene story.
+- Existing kernel-on-sx code in `lib/kernel/` — much of the parser, evaluator structure, and env handling carries over near-verbatim because Kernel and Scheme share lexical scope.
+
+## Progress log
+
+_(awaiting Phase 1)_