giles cf933f0ece 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.

2026-05-13 20:29:37 +00:00

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