4ae3d3116e
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.
299 lines
17 KiB
Scheme
299 lines
17 KiB
Scheme
;; The seq tier on the Chez RT.
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;;
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;; One lazy-capable node (cseq) models Clojure's list, cons, and lazy seq — all
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;; print as (...), all sequential-= to each other AND to vectors. `jolt-seq`
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;; coerces any seqable (vector/map/set/string/list/seq/nil) to a cseq or nil.
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;; The empty seq is a distinct value (jolt-empty-list) that prints "()" — Clojure
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;; (rest [1]) is () not nil, (seq []) is nil. The higher-order fns
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;; (map/filter/reduce/into/remove) apply their fn argument through `jolt-invoke`,
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;; so a procedure, a keyword, or a collection all work as the fn (IFn dispatch).
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;;
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;; Loaded by rt.ss after collections.ss. values.ss / collections.ss reach the
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;; jolt-sequential? / seq=? / seq-hash hooks defined here as forward refs (nothing
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;; is CALLED during load).
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;; ============================================================================
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;; the seq node + the empty-seq sentinel
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;; ============================================================================
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;; head : the realized first element. tail : EITHER a realized seq (cseq |
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;; jolt-nil) when forced? is #t, OR a 0-arg thunk producing one when forced? is
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;; #f. Forcing memoizes (set the tail to the produced seq, flip forced?).
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;; list? : #t when this cell is a PersistentList node (list literal / (list ...)
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;; / cons / reverse / conj-onto-list) vs a lazy or vector-backed seq cell — the
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;; only thing that distinguishes a list from any other realized seq on this host,
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;; since one record type backs both (clojure.core/list?). The marker
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;; lives on the cell, so (rest a-list) / (seq a-vector) / (map …) yield plain seq
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;; cells and are not list?.
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;; cvec/ci: for a vector-backed seq cell, the backing vector and this cell's
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;; element index — so it is a real chunked-seq (chunked-seq? true, chunk-first
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;; hands out a 32-element block, chunk-rest is the seq at the next block) and
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;; reduce iterates the vector directly with no per-element cells.
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;; cvec is #f for every other seq; stored as two fields (not a cons) so a vector
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;; seq cell costs no extra allocation. The rest of the seq layer ignores them, so
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;; first/rest/count/printing are unchanged.
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(define-record-type cseq (fields head (mutable tail) (mutable forced?) list? cvec ci) (nongenerative chez-cseq-v3))
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(define (cseq-realized head tail) (make-cseq head tail #t #f #f 0)) ; tail already a seq
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(define (cseq-lazy head tail-thunk) (make-cseq head tail-thunk #f #f #f 0))
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(define (cseq-list head tail) (make-cseq head tail #t #t #f 0)) ; a PersistentList node
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(define (cseq-vec head tail-thunk v i) (make-cseq head tail-thunk #f #f v i)) ; vector-backed
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(define (seq-first s) (cseq-head s))
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(define (seq-more s) ; force the tail; returns a seq (cseq | jolt-nil)
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(if (cseq-forced? s) (cseq-tail s)
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(let ((t ((cseq-tail s)))) (cseq-tail-set! s t) (cseq-forced?-set! s #t) t)))
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;; The empty seq (Clojure's empty list ()), distinct from nil. The (unused) field
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;; defeats Chez's interning of fieldless records, so an empty list carrying
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;; metadata (an `empty`/`pop`/`with-meta` result) is a distinct identity from the
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;; shared jolt-empty-list — otherwise its meta would leak onto every ().
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(define-record-type empty-list-t (fields _) (nongenerative empty-list-v2))
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(define (fresh-empty-list) (make-empty-list-t #f))
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(define jolt-empty-list (fresh-empty-list))
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;; reduced: a box a reducing fn returns to stop reduce early. The
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;; reduce machinery below unwraps it; (deref a-reduced) / unreduced also read it.
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;; reduced?/reduced are def-var!'d into clojure.core in natives-seq.ss.
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(define-record-type jolt-reduced (fields val) (nongenerative jolt-reduced-v1))
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;; ============================================================================
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;; jolt-seq — coerce a seqable to a non-empty seq, or jolt-nil when empty
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;; ============================================================================
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(define (list->cseq xs) ; Scheme list -> realized cseq chain (jolt-nil if empty)
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(if (null? xs) jolt-nil (cseq-realized (car xs) (list->cseq (cdr xs)))))
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(define (vec->seq v i) ; chunked index seq over a persistent vector
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(if (fx>=? i (pvec-count v)) jolt-nil
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(cseq-vec (pvec-nth-d v i jolt-nil) (lambda () (vec->seq v (fx+ i 1))) v i)))
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(define (str->seq s i)
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(if (fx>=? i (string-length s)) jolt-nil
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(cseq-lazy (string-ref s i) (lambda () (str->seq s (fx+ i 1))))))
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(define (jolt-seq x)
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(cond
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((jolt-nil? x) jolt-nil)
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((empty-list-t? x) jolt-nil)
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((cseq? x) x)
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((pvec? x) (vec->seq x 0))
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((pmap? x) (list->cseq (pmap-fold x (lambda (k v a) (cons (make-map-entry k v) a)) '())))
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((pset? x) (list->cseq (pset-fold x cons '())))
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((string? x) (str->seq x 0))
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(else (error 'seq "not seqable" x))))
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(define (jolt-sequential? x) (or (pvec? x) (cseq? x) (empty-list-t? x)))
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(define (seq->list s) ; force a finite seq to a Scheme list
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(let loop ((s (jolt-seq s)) (acc '()))
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(if (jolt-nil? s) (reverse acc) (loop (jolt-seq (seq-more s)) (cons (seq-first s) acc)))))
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;; ============================================================================
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;; the seq leaf ops the emitter lowers core fns to
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;; ============================================================================
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(define (jolt-first x) (let ((s (jolt-seq x))) (if (jolt-nil? s) jolt-nil (seq-first s))))
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(define (jolt-rest x) ; () when the seq has 0/1 elements (NOT nil)
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(let ((s (jolt-seq x)))
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(if (jolt-nil? s) jolt-empty-list
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(let ((m (seq-more s))) (if (jolt-nil? m) jolt-empty-list m)))))
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(define (jolt-next x) ; nil when the rest is empty
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;; next = (seq (rest x)): the rest must be RE-SEQ'd so an empty tail collapses to
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;; nil. seq-more on a lazy seq (e.g. map's) forces to jolt-empty-list, which is
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;; truthy — returning it raw made (next 1-elem-lazy-seq) non-nil, so butlast and
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;; other (if (next s) ...) loops over a lazy seq ran one step too far.
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(let ((s (jolt-seq x))) (if (jolt-nil? s) jolt-nil (jolt-seq (seq-more s)))))
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;; Only the HEAD cell carries the list marker — (rest a-list)/(next a-list) return
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;; the unmarked tail, so they are seqs and not list? (rest-of-a-list is a non-list
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;; seq). cons/list/reverse/conj therefore mark
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;; just the cell they create.
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;;
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;; cons always yields a list — (list? (cons x anything)) is true (cons
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;; onto a vector/seq/nil all report list?).
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(define (jolt-cons x coll) (cseq-list x (jolt-seq coll)))
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;; Scheme list -> a jolt PersistentList: head is a list cell, the tail chain is
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;; plain seq cells. For (list …) and quoted list literals (the emitter lowers
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;; '(a b) to (jolt-list a b)).
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(define (jolt-list . xs)
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(if (null? xs) jolt-empty-list (cseq-list (car xs) (list->cseq (cdr xs)))))
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;; reverse yields a list (seed: (list? (reverse coll)) is always true). Build a
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;; plain seq chain, then mark its head as a list cell.
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(define (jolt-reverse coll)
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(let loop ((s (jolt-seq coll)) (acc jolt-empty-list))
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(if (jolt-nil? s)
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(if (empty-list-t? acc) acc (cseq-list (seq-first acc) (seq-more acc)))
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(loop (jolt-seq (seq-more s)) (cseq-realized (seq-first s) (if (empty-list-t? acc) jolt-nil acc))))))
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(define (jolt-last coll) (let loop ((s (jolt-seq coll)) (last jolt-nil))
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(if (jolt-nil? s) last (loop (jolt-seq (seq-more s)) (seq-first s)))))
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;; nth over a seq (walks; forces lazily). default? selects the 3-arg behavior.
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(define (seq-nth coll i default? d)
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(if (fx<? i 0) (if default? d (error 'nth "index out of bounds"))
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(let loop ((s (jolt-seq coll)) (i i))
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(cond ((jolt-nil? s) (if default? d (error 'nth "index out of bounds")))
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((fx=? i 0) (seq-first s))
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(else (loop (jolt-seq (seq-more s)) (fx- i 1)))))))
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;; value-position arithmetic (the higher-order forms: (reduce + []), (apply * xs)).
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;; Scheme's +/-/*// already implement the JVM-parity numeric tower: exact+exact ->
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;; exact, exact/exact -> Ratio, any flonum -> flonum. Identities (+)=0 / (*)=1 are
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;; exact, matching exact integer arithmetic. The hot path uses the inlined native
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;; ops, not these.
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(define (jolt-add . xs) (apply + xs))
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(define (jolt-sub . xs) (apply - xs))
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(define (jolt-mul . xs) (apply * xs))
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(define (jolt-div . xs) (apply / xs))
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;; ============================================================================
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;; IFn dispatch — the dynamic "value as fn" fallback. A callee that the emitter
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;; can't statically resolve to a procedure (a keyword/coll/proc held in a local)
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;; routes here. Off the arithmetic/self-recursion hot path by construction.
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;; ============================================================================
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(define (jolt-invoke f . args)
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(cond
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((procedure? f) (apply f args))
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((keyword? f) (apply jolt-get (car args) f (cdr args))) ; (:k m [d]) -> (get m :k [d])
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((jolt-coll? f) (apply jolt-get f args)) ; (coll k [d]) -> (get coll k [d])
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((jolt-transient? f) (apply jolt-get f args)) ; a transient vec/map/set is callable on the JVM
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(else (error 'invoke "not a fn" f))))
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;; ============================================================================
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;; map / filter / reduce / into / remove + range / take / concat / apply
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;; ============================================================================
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(define (any-nil? seqs) (and (pair? seqs) (or (jolt-nil? (car seqs)) (any-nil? (cdr seqs)))))
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;; An EMPTY seq result is () (jolt-empty-list), NOT nil — Clojure's (map f []) is
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;; an empty seq, so (= () (map f [])) is true and (nil? (map f [])) is false.
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;; jolt-empty-list seqs back to nil, so it stays a valid lazy-tail terminator for
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;; the non-empty case (printing / seq= / reduce all walk via jolt-seq).
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(define (map-seq f s)
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(if (jolt-nil? s) jolt-empty-list
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(cseq-lazy (jolt-invoke f (seq-first s)) (lambda () (map-seq f (jolt-seq (seq-more s)))))))
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(define (map-seq* f seqs) ; multi-collection map; stops at the shortest
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(if (any-nil? seqs) jolt-empty-list
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(cseq-lazy (apply jolt-invoke f (map seq-first seqs))
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(lambda () (map-seq* f (map (lambda (s) (jolt-seq (seq-more s))) seqs))))))
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(define (jolt-map f . colls)
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(if (null? (cdr colls))
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(map-seq f (jolt-seq (car colls)))
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(map-seq* f (map jolt-seq colls))))
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(define (filter-seq pred s keep)
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(let loop ((s s))
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(cond ((jolt-nil? s) jolt-empty-list) ; empty result is () (see map-seq)
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((eq? keep (jolt-truthy? (jolt-invoke pred (seq-first s))))
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(cseq-lazy (seq-first s) (lambda () (filter-seq pred (jolt-seq (seq-more s)) keep))))
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(else (loop (jolt-seq (seq-more s)))))))
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(define (jolt-filter pred coll) (filter-seq pred (jolt-seq coll) #t))
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(define (jolt-remove pred coll) (filter-seq pred (jolt-seq coll) #f))
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;; honors `reduced`: a reducing fn that returns (reduced x) stops the fold and
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;; unwraps to x (so does a reduced INIT). Checked at entry, so the value returned
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;; by the last step is unwrapped on the next turn before the seq is consulted.
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;; reduce a vector's backing store directly by index from element i — no per-
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;; element seq cells. Honors `reduced`. The chunked-seq fast path.
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(define (vec-reduce f acc v i)
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(let ((n (pvec-count v)) (raw (pvec-v v)))
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(let loop ((i i) (acc acc))
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(cond ((jolt-reduced? acc) (jolt-reduced-val acc))
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((fx>=? i n) acc)
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(else (loop (fx+ i 1) (jolt-invoke f acc (vector-ref raw i))))))))
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(define (reduce-seq f acc s)
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(cond
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((jolt-reduced? acc) (jolt-reduced-val acc))
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((jolt-nil? s) acc)
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;; a vector-backed (chunked) seq reduces its vector directly, in a tight loop.
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((and (cseq? s) (cseq-cvec s)) (vec-reduce f acc (cseq-cvec s) (cseq-ci s)))
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(else (reduce-seq f (jolt-invoke f acc (seq-first s)) (jolt-seq (seq-more s))))))
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(define jolt-reduce
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(case-lambda
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((f coll) (let ((s (jolt-seq coll)))
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(if (jolt-nil? s) (jolt-invoke f) ; (reduce f []) -> (f)
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(reduce-seq f (seq-first s) (jolt-seq (seq-more s))))))
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((f init coll)
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;; IReduceInit: a reify/record with its own `reduce` method drives the
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;; reduction (reduce f init (reify clojure.lang.IReduceInit (reduce [_ f i] ...))).
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(cond
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((and (jreify? coll) (reified-methods coll)
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(hashtable-ref (reified-methods coll) "reduce" #f))
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=> (lambda (m) (let ((r (jolt-invoke m coll f init)))
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(if (jolt-reduced? r) (jolt-reduced-val r) r))))
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(else (reduce-seq f init (jolt-seq coll)))))))
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;; Fold through a transient so a pvec/pmap/pset target is built in O(n): a
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;; persistent pvec-conj copies its whole backing vector each step, making a naive
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;; fold O(n^2) (and into/vec/mapv/filterv all route here). jolt-transient-new
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;; falls back to a copy-on-write wrapper for other targets (lists, sorted colls,
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;; nil), so those keep the old per-step jolt-conj behaviour.
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(define (jolt-into to from)
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(meta-carry to
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(jolt-persistent! (reduce-seq (lambda (t x) (jolt-conj! t x)) (jolt-transient-new to) (jolt-seq from)))))
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(define (range-from n) (cseq-lazy n (lambda () (range-from (+ n 1)))))
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(define (range-bounded n end step)
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(if (if (> step 0.0) (< n end) (> n end))
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(cseq-lazy n (lambda () (range-bounded (+ n step) end step)))
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jolt-nil))
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;; numeric tower: exact 0/1 defaults so (range 3) yields exact ints
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;; (= JVM longs); flonum args still produce flonums (Scheme arithmetic preserves).
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(define jolt-range
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(case-lambda
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(() (range-from 0))
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((end) (range-bounded 0 end 1))
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((start end) (range-bounded start end 1))
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((start end step) (range-bounded start end step))))
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(define (jolt-take n coll)
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(let ((n (->idx n)))
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(let loop ((n n) (s (jolt-seq coll)))
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(if (or (fx<=? n 0) (jolt-nil? s)) jolt-nil
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(cseq-lazy (seq-first s) (lambda () (loop (fx- n 1) (jolt-seq (seq-more s)))))))))
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(define (jolt-drop n coll)
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(let loop ((n (->idx n)) (s (jolt-seq coll)))
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(if (or (fx<=? n 0) (jolt-nil? s)) (if (jolt-nil? s) jolt-empty-list s)
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(loop (fx- n 1) (jolt-seq (seq-more s))))))
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;; lazily append seq a then the seqable produced by the thunk `brest` — the rest
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;; is NOT forced until a is exhausted, so concat is fully lazy (Clojure semantics).
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;; This matters for a self-referential lazy-cat (fib = (lazy-cat [0 1] (map + (rest
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;; fib) fib))): forcing the rest eagerly at construction would read fib before its
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;; def binds, memoizing the tail as empty.
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(define (concat2 a brest)
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(if (jolt-nil? a) (jolt-seq (brest))
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(cseq-lazy (seq-first a) (lambda () (concat2 (jolt-seq (seq-more a)) brest)))))
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(define (jolt-concat . colls)
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(cond ((null? colls) jolt-empty-list)
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((null? (cdr colls)) (jolt-seq (car colls)))
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(else (concat2 (jolt-seq (car colls)) (lambda () (apply jolt-concat (cdr colls)))))))
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;; (apply f a b ... coll): spread the trailing seqable into the call.
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(define (jolt-apply f . args)
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(let* ((r (reverse args)) (spread (seq->list (jolt-seq (car r)))) (fixed (reverse (cdr r))))
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(apply jolt-invoke f (append fixed spread))))
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;; ============================================================================
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;; numeric predicates / identity — usable in fn AND value position (map/filter).
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;; Return Scheme #t/#f (= jolt true/false). All-flonum model: coerce to an exact
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;; integer for the parity tests.
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;; ============================================================================
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;; Parity over the full integer range (JVM even?/odd? accept any integer,
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;; bignums included); a fixnum-only fxand crashes on a large value (e.g. a hash).
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(define (parity-int n) (if (flonum? n) (exact (floor n)) n))
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(define (jolt-even? n) (even? (parity-int n)))
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(define (jolt-odd? n) (odd? (parity-int n)))
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(define (jolt-pos? n) (> n 0))
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(define (jolt-neg? n) (< n 0))
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(define (jolt-zero? n) (= n 0))
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(define (jolt-identity x) x)
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;; ============================================================================
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;; keys / vals — return seqs (nil on the empty map), HAMT-iteration order
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;; ============================================================================
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(define (jolt-keys m) (if (jolt-nil? m) jolt-nil (list->cseq (pmap-fold m (lambda (k v a) (cons k a)) '()))))
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(define (jolt-vals m) (if (jolt-nil? m) jolt-nil (list->cseq (pmap-fold m (lambda (k v a) (cons v a)) '()))))
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;; ============================================================================
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;; sequential equality + hash (hooks called from values.ss / collections.ss);
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;; consistent with the persistent vector's element-wise =/hash so a vector and a
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;; list of the same elements are jolt= and hash alike.
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;; ============================================================================
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(define (seq=? a b)
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(let loop ((sa (jolt-seq a)) (sb (jolt-seq b)))
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(cond ((and (jolt-nil? sa) (jolt-nil? sb)) #t)
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((or (jolt-nil? sa) (jolt-nil? sb)) #f)
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((jolt= (seq-first sa) (seq-first sb)) (loop (jolt-seq (seq-more sa)) (jolt-seq (seq-more sb))))
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(else #f))))
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(define (seq-hash x)
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(let loop ((s (jolt-seq x)) (h 1))
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(if (jolt-nil? s) (bitwise-and h hmask)
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(loop (jolt-seq (seq-more s)) (bitwise-and (+ (* 31 h) (key-hash (seq-first s))) hmask)))))
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