b3d0a91e3e
0c: persistent HAMT on Chez is ~41x faster than Janet's HAMT on the collections map-churn (258.6 -> 6.3 ms), ~15x off mutable-native (inherent persistence cost). Decision: self-host the persistent collections in Clojure; substrate is not the bottleneck. See docs/chez-phase0-results.md. 0a hardening: NUL-separated keyword intern key (no ns/name collision), non-finite -safe jolt-hash. 37/37.
81 lines
3.8 KiB
Scheme
81 lines
3.8 KiB
Scheme
;; Jolt value model on Chez Scheme — Phase 0a (jolt-cf1q.1).
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;;
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;; The irreducible value layer the self-hosted RT rests on. Maps Clojure's value
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;; types onto Chez natives where possible, and adds records only where Chez lacks
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;; a distinct type (nil sentinel, keywords, ns-bearing symbols). Loaded into an
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;; env that has already (import (chezscheme)); becomes a real library in Phase 1.
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;;
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;; Design notes:
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;; - nil is a UNIQUE sentinel, distinct from #f and '() (the classic Lisp-on-Lisp
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;; trap). jolt false -> Chez #f, jolt true -> #t.
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;; - Chez's numeric tower IS Clojure's: long->exact integer, double->flonum,
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;; ratio->exact rational, bigint->bignum. A windfall vs Janet (ratios/bignums
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;; for free). Clojure `=` is exactness-aware: (= 1 1.0) is FALSE.
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;; --- nil ---------------------------------------------------------------------
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(define-record-type jolt-nil-t (fields) (nongenerative jolt-nil-v1))
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(define jolt-nil (make-jolt-nil-t))
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(define (jolt-nil? x) (jolt-nil-t? x))
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;; --- truthiness: only nil and false are falsey -------------------------------
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(define (jolt-truthy? x) (not (or (jolt-nil? x) (eq? x #f))))
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;; --- keywords: interned so identity works; optional namespace ----------------
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(define-record-type keyword-t (fields ns name khash) (nongenerative keyword-v1))
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(define keyword-table (make-hashtable string-hash string=?))
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;; NUL separator can't occur in a keyword ns/name, so the intern key is
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;; unambiguous (a "/" separator would collide ns="a" name="b/c" with ns="a/b").
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(define (keyword-intern-key ns name) (string-append (or ns "") "\x0;" name))
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(define (keyword ns name)
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(let ((k (keyword-intern-key ns name)))
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(or (hashtable-ref keyword-table k #f)
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(let ((kw (make-keyword-t ns name (equal-hash k))))
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(hashtable-set! keyword-table k kw)
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kw))))
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(define (keyword? x) (keyword-t? x))
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;; --- symbols: ns + name + meta; NOT interned (meta varies), = by ns/name ------
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(define-record-type symbol-t (fields ns name meta) (nongenerative symbol-v1))
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(define (jolt-symbol ns name) (make-symbol-t ns name jolt-nil))
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(define (jolt-symbol/meta ns name meta) (make-symbol-t ns name meta))
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(define (jolt-symbol? x) (symbol-t? x))
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;; chars/strings: Chez natives (strings treated immutable).
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;; --- jolt equality (Clojure =) — scalars; collections land in Phase 2 --------
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(define (jolt=2 a b)
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(cond
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((and (jolt-nil? a) (jolt-nil? b)) #t)
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((or (jolt-nil? a) (jolt-nil? b)) #f)
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((and (number? a) (number? b)) ; exactness-aware
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(and (eq? (exact? a) (exact? b)) (= a b)))
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((and (keyword-t? a) (keyword-t? b)) (eq? a b)) ; interned
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((and (symbol-t? a) (symbol-t? b))
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(and (equal? (symbol-t-ns a) (symbol-t-ns b))
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(string=? (symbol-t-name a) (symbol-t-name b))))
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((and (char? a) (char? b)) (char=? a b))
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((and (string? a) (string? b)) (string=? a b))
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((and (boolean? a) (boolean? b)) (eq? a b))
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(else (eq? a b))))
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(define (jolt= a . rest)
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(let loop ((a a) (rest rest))
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(cond ((null? rest) #t)
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((jolt=2 a (car rest)) (loop (car rest) (cdr rest)))
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(else #f))))
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;; --- jolt hash — consistent with jolt= (for the HAMT in 0c / Phase 2) ---------
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(define (jolt-hash x)
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(cond
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((jolt-nil? x) 0)
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((keyword-t? x) (keyword-t-khash x))
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((symbol-t? x) (equal-hash (cons (symbol-t-ns x) (symbol-t-name x))))
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;; distinguish inexact from exact (1 and 1.0 are not jolt=); guard non-finite
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;; (inexact->exact would error on NaN/inf)
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((number? x) (if (exact? x) (equal-hash x)
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(if (and (flonum? x) (or (nan? x) (infinite? x)))
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(equal-hash (cons 'inexact (number->string x)))
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(equal-hash (cons 'inexact (inexact->exact x))))))
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((string? x) (string-hash x))
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((char? x) (char->integer x))
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((boolean? x) (if x 1 2))
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(else (equal-hash x))))
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