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Collection ops carry the receiver's metadata

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conj/assoc/dissoc/disj/pop/into and empty now thread the receiver's
metadata onto the result, matching Clojure (each op constructs a new
collection with meta() carried forward; coll.empty() is
EMPTY.withMeta(meta())). The metadata side-table is now weak so meta on
intermediate collections is reclaimed with them, and empty-list-t carries
an (unused) field so a metadata-bearing () is a distinct identity from the
shared singleton instead of leaking meta onto every ().

Unblocks metadata-driven walks (aero/integrant): (into (empty form) ...)
now preserves a vector/map/set's metadata, so a postwalk whose outer fn
reads (meta x) sees it.
This commit is contained in:
Yogthos 2026-06-24 13:46:58 -04:00
parent 5b55c7f7b0
commit 4ae3d3116e
7 changed files with 484 additions and 457 deletions
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13
host/chez/seq.ss
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@ -41,9 +41,13 @@
(if (cseq-forced? s) (cseq-tail s)
(let ((t ((cseq-tail s)))) (cseq-tail-set! s t) (cseq-forced?-set! s #t) t)))
;; The empty seq (Clojure's empty list ()), distinct from nil.
(define-record-type empty-list-t (fields) (nongenerative empty-list-v1))
(define jolt-empty-list (make-empty-list-t))
;; The empty seq (Clojure's empty list ()), distinct from nil. The (unused) field
;; defeats Chez's interning of fieldless records, so an empty list carrying
;; metadata (an `empty`/`pop`/`with-meta` result) is a distinct identity from the
;; shared jolt-empty-list — otherwise its meta would leak onto every ().
(define-record-type empty-list-t (fields _) (nongenerative empty-list-v2))
(define (fresh-empty-list) (make-empty-list-t #f))
(define jolt-empty-list (fresh-empty-list))
;; reduced: a box a reducing fn returns to stop reduce early. The
;; reduce machinery below unwraps it; (deref a-reduced) / unreduced also read it.
@ -212,7 +216,8 @@
;; falls back to a copy-on-write wrapper for other targets (lists, sorted colls,
;; nil), so those keep the old per-step jolt-conj behaviour.
(define (jolt-into to from)
(jolt-persistent! (reduce-seq (lambda (t x) (jolt-conj! t x)) (jolt-transient-new to) (jolt-seq from))))
(meta-carry to
(jolt-persistent! (reduce-seq (lambda (t x) (jolt-conj! t x)) (jolt-transient-new to) (jolt-seq from)))))
(define (range-from n) (cseq-lazy n (lambda () (range-from (+ n 1)))))
(define (range-bounded n end step)