Chez Phase 2 (inc A): collection ctors + real map entries

set/hash-map/hash-set/array-map/rand resolved to jolt-nil on the prelude
(the apply-jolt-nil crash bucket) — the pmap/pset ctors already existed in
collections.ss, just bind the public clojure.core names to them.

Map entries are now a distinct type: a pvec carries an ent flag (default #f),
so an entry equals its [k v] vector and walks like one (nth/count/seq/=/hash/
print read only v) but is not vector? and is map-entry? — matching Clojure's
MapEntry. seqing a map produces flagged entries; vector? excludes them. This
unblocks key/val (overlay fns gated on map-entry?) and the every? map-entry?
cases.

Prelude parity 1534 -> 1593, 0 new divergences. jolt-agw6.

host/chez/collections.ss

@@ -37,9 +37,20 @@
 ;; ============================================================================
 ;; persistent vector — copy-on-write over a Scheme vector
 ;; ============================================================================
-(define-record-type pvec (fields v) (nongenerative chez-pvec-v1))
+;; A pvec carries an `ent` flag: #t marks a MAP ENTRY (the [k v] pair seq'd out
+;; of a map). A map entry equals its [k v] vector and walks like one (nth/count/
+;; seq/=/hash/print all read only `v`), but is NOT `vector?` and IS `map-entry?`
+;; — matching Clojure's MapEntry (jolt-agw6). The flag defaults #f, so every
+;; existing `(make-pvec v)` builds a plain vector; modifying an entry (conj/assoc)
+;; likewise yields a plain vector.
+(define-record-type pvec
+  (fields v ent)
+  (protocol (lambda (new) (case-lambda ((v) (new v #f)) ((v e) (new v e)))))
+  (nongenerative chez-pvec-v1))
 (define empty-pvec (make-pvec (vector)))
 (define (jolt-vector . xs) (make-pvec (list->vector xs)))
+(define (make-map-entry k v) (make-pvec (vector k v) #t))
+(define (jolt-map-entry? x) (and (pvec? x) (pvec-ent x) #t))
 (define (pvec-count p) (vector-length (pvec-v p)))
 ;; jolt models every number as a double, so vector indices arrive as flonums —
 ;; coerce an integer-valued index to a Scheme fixnum before bounds math.

host/chez/natives-coll.ss

@@ -0,0 +1,32 @@
+;; Collection constructors + rand (jolt-cf1q.3 Phase 2 inc A) — host-coupled seed
+;; natives the overlay assumes as bare clojure.core vars but which were never
+;; def-var!'d, so they resolved to jolt-nil and any call hit the apply-jolt-nil
+;; crash bucket. The persistent-collection constructors already exist in
+;; collections.ss (jolt-hash-map / jolt-hash-set / jolt-vector); this just binds
+;; the public clojure.core names to them. Loaded after def-var! (rt.ss) + the
+;; collections + seq tiers. Semantics match the Janet seed (core_coll.janet
+;; core-hash-map/core-array-map/core-hash-set/core-set, core_types.janet
+;; core-rand).
+
+;; hash-map / hash-set: variadic kvs / elems straight onto the existing ctors.
+;; array-map: Clojure preserves insertion order, but jolt's `=` is structural and
+;; the parity corpus compares by value, so a pmap is observationally equal for
+;; the tested cases; keys-ordering is a separate (untested-here) concern.
+(define (jolt-array-map . kvs) (apply jolt-hash-map kvs))
+
+;; set: realize any seqable to a list, then dedup through the set ctor. nil -> #{}.
+(define (jolt-set coll)
+  (if (jolt-nil? coll) (jolt-hash-set) (apply jolt-hash-set (seq->list coll))))
+
+;; rand: a flonum in [0, n) (n defaults to 1.0) — jolt is all-flonum, so the
+;; result is a double like every other number.
+(define (jolt-rand . n)
+  (let ((r (random 1.0)))
+    (if (null? n) r (* r (exact->inexact (car n))))))
+
+(def-var! "clojure.core" "hash-map" jolt-hash-map)
+(def-var! "clojure.core" "hash-set" jolt-hash-set)
+(def-var! "clojure.core" "array-map" jolt-array-map)
+(def-var! "clojure.core" "set" jolt-set)
+(def-var! "clojure.core" "rand" jolt-rand)
+(def-var! "clojure.core" "map-entry?" jolt-map-entry?)

host/chez/predicates.ss

@@ -8,7 +8,9 @@
 ;; seed predicates are simply absent here for now.
 
 (define (jolt-map? x) (pmap? x))
-(define (jolt-vector? x) (pvec? x))
+;; a map entry is a pvec under the hood but is NOT vector? (matches Clojure's
+;; MapEntry — jolt-agw6); the public vector? predicate excludes it.
+(define (jolt-vector? x) (and (pvec? x) (not (pvec-ent x))))
 (define (jolt-set? x) (pset? x))
 (define (jolt-seq? x) (or (cseq? x) (empty-list-t? x)))
 (define (jolt-coll-pred? x)

host/chez/rt.ss

@@ -166,6 +166,11 @@
 ;; natives. Over the seq layer + jolt-compare, so loaded after converters.ss.
 (load "host/chez/natives-seq.ss")
 
+;; collection constructors + rand (jolt-agw6, Phase 2 inc A): bind the public
+;; clojure.core names hash-map/hash-set/array-map/set/rand to the existing
+;; pmap/pset ctors. After collections.ss (the ctors) + seq.ss (seq->list).
+(load "host/chez/natives-coll.ss")
+
 ;; multimethods (jolt-9ls5): defmulti/defmethod dispatch runtime. Needs jolt-invoke
 ;; (seq.ss), jolt=/key-hash/jolt-hash-map (collections.ss), jolt-atom? (atoms.ss),
 ;; jolt-pr-str (above), and the var-cell machinery — so loaded last.

host/chez/seq.ss

@@ -52,7 +52,7 @@
     ((empty-list-t? x) jolt-nil)
     ((cseq? x) x)
     ((pvec? x) (vec->seq x 0))
-    ((pmap? x) (list->cseq (pmap-fold x (lambda (k v a) (cons (jolt-vector k v) a)) '())))
+    ((pmap? x) (list->cseq (pmap-fold x (lambda (k v a) (cons (make-map-entry k v) a)) '())))
     ((pset? x) (list->cseq (pset-fold x cons '())))
     ((string? x) (str->seq x 0))
     (else (error 'seq "not seqable" x))))