48e2ef5910
Rephrase comments that pointed at deleted Janet files (emit.janet, the seed
sources, 'the Janet back end punts ...') to present-tense descriptions of the
Chez behavior. Comment/docstring-only; the self-host fixpoint is unchanged
(comments don't affect the compiled seed).
Delete five files that were Janet-host shims with no Chez path: clojure.java.io
(provided natively by host/chez/io.ss), and jolt.{nrepl,png,interop,shell}
(the janet.* bridge, os/shell, janet.net — none exist on Chez).
jolt-cf1q.6
146 lines
6.6 KiB
Scheme
146 lines
6.6 KiB
Scheme
;; atoms (jolt-9ziu) — host-coupled mutable reference cells for the Chez host.
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;;
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;; atom/deref/swap!/reset! are host primitives (not the clojure.core overlay),
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;; so the Chez runtime provides native shims, def-var!'d into clojure.core. They
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;; lower to var-deref in prelude mode. The hierarchy machinery
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;; (global-hierarchy = (atom (make-hierarchy))) calls `atom` at the prelude's
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;; LOAD time, so without this shim the whole prelude fails to load.
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;;
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;; compare-and-set!/swap-vals!/reset-vals! are overlay fns over the native kernel
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;; in the live system; provided here natively too so the Chez host is
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;; self-sufficient for atoms without the full prelude (the overlay versions, when
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;; the full prelude loads, override these but compose the same native kernel).
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;; watches is an alist of (key . watch-fn); validator is a jolt fn or jolt-nil.
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;; The overlay's add-watch/set-validator! drive these via jolt.host/ref-put! on a
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;; Janet table, which a Chez atom record is not — so the peripheral ops + the
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;; notify/validate behaviour live natively here, and post-prelude.ss re-asserts
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;; them over the overlay's def-var! (jolt-mn9o).
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;; `lock` (jolt-byjr) is a per-atom mutex guarding the read-modify-write critical
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;; sections, so swap!/reset!/compare-and-set! are atomic under real OS threads
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;; (futures/go blocks share the heap on Chez). The user fn in swap! runs OUTSIDE
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;; the lock (a CAS retry loop, like the JVM) so it never deadlocks on re-entrant
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;; access and a watch/validator can deref the same atom.
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(define-record-type jolt-atom
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(fields (mutable val) (mutable watches) (mutable validator) lock)
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(nongenerative jolt-atom-v3))
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;; (atom init) / (atom init :validator f :meta m): scan the trailing keyword opts
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;; for :validator (the only one with runtime behaviour; :meta is accepted/ignored).
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(define (jolt-atom-new v . opts)
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(let loop ((o opts) (validator jolt-nil))
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(cond
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((or (null? o) (null? (cdr o))) (make-jolt-atom v '() validator (make-mutex)))
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((and (keyword-t? (car o)) (string=? (keyword-t-name (car o)) "validator"))
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(loop (cddr o) (cadr o)))
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(else (loop (cddr o) validator)))))
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;; validate a candidate value: a non-nil validator that returns falsey rejects.
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(define (jolt-atom-validate a v)
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(let ((vf (jolt-atom-validator a)))
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(when (and (not (jolt-nil? vf)) (jolt-not (jolt-invoke vf v)))
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(error #f "Invalid reference state"))))
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;; notify each watch (k ref old new), in insertion order (alist is reverse-built,
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;; so walk it reversed to match add order).
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(define (jolt-atom-notify a old new)
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(for-each (lambda (kv) (jolt-invoke (cdr kv) (car kv) a old new))
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(reverse (jolt-atom-watches a))))
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;; deref reads an atom; it also unwraps a `reduced` (Clojure @(reduced x) => x,
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;; which the overlay's `unreduced` relies on). The reduced record is in seq.ss.
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(define (jolt-deref x)
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(cond
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((jolt-atom? x) (jolt-atom-val x))
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((jolt-reduced? x) (jolt-reduced-val x))
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(else (error #f "deref: unsupported reference type" x))))
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;; CAS the val from `old` to `nv` by identity (eq?), atomically. Returns #t on
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;; success. The compute step (f) runs outside this, so we re-check under the lock.
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(define (jolt-atom-cas! a old nv)
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(with-mutex (jolt-atom-lock a)
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(if (eq? (jolt-atom-val a) old)
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(begin (jolt-atom-val-set! a nv) #t)
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#f)))
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;; (swap! a f arg*): JVM-style CAS loop — read, compute f OUTSIDE the lock, then
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;; atomically compare-and-set; retry if another thread changed it. Validate the
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;; new value before storing, notify watches after.
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(define (jolt-swap! a f . args)
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(let retry ()
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(let* ((old (jolt-atom-val a))
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(nv (apply jolt-invoke f old args)))
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(jolt-atom-validate a nv)
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(if (jolt-atom-cas! a old nv)
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(begin (jolt-atom-notify a old nv) nv)
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(retry)))))
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(define (jolt-reset! a v)
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(jolt-atom-validate a v)
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(let ((old (with-mutex (jolt-atom-lock a)
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(let ((o (jolt-atom-val a))) (jolt-atom-val-set! a v) o))))
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(jolt-atom-notify a old v)
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v))
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;; compare-and-set! keeps jolt= (value) semantics, done atomically under the lock.
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(define (jolt-compare-and-set! a oldv newv)
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(jolt-atom-validate a newv)
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(let ((swapped (with-mutex (jolt-atom-lock a)
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(if (jolt= (jolt-atom-val a) oldv)
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(begin (jolt-atom-val-set! a newv) #t)
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#f))))
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(when swapped (jolt-atom-notify a oldv newv))
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swapped))
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(define (jolt-swap-vals! a f . args)
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(let retry ()
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(let* ((old (jolt-atom-val a))
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(nv (apply jolt-invoke f old args)))
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(jolt-atom-validate a nv)
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(if (jolt-atom-cas! a old nv)
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(begin (jolt-atom-notify a old nv) (jolt-vector old nv))
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(retry)))))
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(define (jolt-reset-vals! a v)
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(jolt-atom-validate a v)
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(let ((old (with-mutex (jolt-atom-lock a)
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(let ((o (jolt-atom-val a))) (jolt-atom-val-set! a v) o))))
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(jolt-atom-notify a old v)
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(jolt-vector old v)))
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;; --- watches / validators (jolt-mn9o) ---------------------------------------
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;; add-watch interns (key . fn) (replacing any existing key, keeping order);
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;; remove-watch drops it; both return the atom. set-validator! installs a
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;; validator and validates the CURRENT value immediately (Clojure throws if it's
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;; already invalid); get-validator reads the slot.
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(define (jolt-add-watch a key f)
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(jolt-atom-watches-set! a
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(cons (cons key f)
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(remp (lambda (kv) (jolt=2 (car kv) key)) (jolt-atom-watches a))))
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a)
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(define (jolt-remove-watch a key)
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(jolt-atom-watches-set! a
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(remp (lambda (kv) (jolt=2 (car kv) key)) (jolt-atom-watches a)))
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a)
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(define (jolt-set-validator! a f)
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(let ((vf (if (jolt-nil? f) jolt-nil f)))
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(when (and (not (jolt-nil? vf)) (jolt-not (jolt-invoke vf (jolt-atom-val a))))
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(error #f "Invalid reference state"))
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(jolt-atom-validator-set! a vf)
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jolt-nil))
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(define (jolt-get-validator a) (jolt-atom-validator a))
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(def-var! "clojure.core" "atom" jolt-atom-new)
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(def-var! "clojure.core" "deref" jolt-deref)
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(def-var! "clojure.core" "swap!" jolt-swap!)
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(def-var! "clojure.core" "reset!" jolt-reset!)
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(def-var! "clojure.core" "compare-and-set!" jolt-compare-and-set!)
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(def-var! "clojure.core" "swap-vals!" jolt-swap-vals!)
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(def-var! "clojure.core" "reset-vals!" jolt-reset-vals!)
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(def-var! "clojure.core" "atom?" jolt-atom?)
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;; peripheral ops: the overlay (20-coll) re-defs these over jolt.host/ref-put!,
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;; which fails on a Chez atom record — post-prelude.ss re-asserts the natives.
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(def-var! "clojure.core" "add-watch" jolt-add-watch)
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(def-var! "clojure.core" "remove-watch" jolt-remove-watch)
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(def-var! "clojure.core" "set-validator!" jolt-set-validator!)
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(def-var! "clojure.core" "get-validator" jolt-get-validator)
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