scheme: Phase 4 standard env + set! bugfix + 78 tests
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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.
This commit is contained in:
2026-05-13 20:29:37 +00:00
parent 0fccd1b353
commit cf933f0ece
3 changed files with 729 additions and 2 deletions

513
lib/scheme/runtime.sx Normal file
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;; 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)))