giles f927fb6515 scheme: Phase 9 — define-record-type + 9 tests ...

eval.sx adds the define-record-type syntactic operator:

  (define-record-type NAME
    (CONSTRUCTOR ARG...)
    PREDICATE
    (FIELD ACCESSOR [MUTATOR])...)

Records are tagged dicts:
  {:scm-record TYPE-NAME :fields {FIELD VALUE ...}}

For each record type, the operator binds:
- Constructor: takes the listed ARGs, populates :fields, returns
  the record. Fields not in CONSTRUCTOR ARGs default to nil.
- Predicate: returns true iff its arg is a record of THIS type
  (tag-match via :scm-record).
- Accessor per field: extracts the field value; errors if not
  a record of the right type.
- Mutator per field (optional): sets the field via dict-set!;
  same type-check.

Distinct types are isolated via their tag — point? returns false
on a circle, even if both have the same shape.

9 tests cover: constructor + predicate + accessors, mutator,
distinct-types-via-tag, records as first-class values (in lists,
passed to map/filter), constructor arity errors.

289 total Scheme tests (62+23+49+78+25+20+13+10+9).

2026-05-14 06:49:24 +00:00

33 KiB

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