ice-9/hcons.scm

   1 ;;; installed-scm-file
   2
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  44
  45 \f
  46 (define-module  (ice-9 hcons))
  47
  48 \f
  49 ;;; {Eq? hash-consing}
  50 ;;;
  51 ;;; A hash conser maintains a private universe of pairs s.t. if
  52 ;;; two cons calls pass eq? arguments, the pairs returned are eq?.
  53 ;;;
  54 ;;; A hash conser does not contribute life to the pairs it returns.
  55 ;;;
  56
  57 (define-public (hashq-cons-hash pair n)
  58   (modulo (logxor (hashq (car pair) 4194303)
  59                   (hashq (cdr pair) 4194303))
  60           n))
  61
  62 (define-public (hashq-cons-assoc key l)
  63   (and (not (null? l))
  64        (or (and (pair? l)               ; If not a pair, use its cdr?
  65                 (pair? (car l))
  66                 (pair? (caar l))
  67                 (eq? (car key) (caaar l))
  68                 (eq? (cdr key) (cdaar l))
  69                 (car l))
  70            (hashq-cons-assoc key (cdr l)))))
  71
  72 (define-public (hashq-cons-get-handle table key)
  73   (hashx-get-handle hashq-cons-hash hashq-cons-assoc table key #f))
  74
  75 (define-public (hashq-cons-create-handle! table key init)
  76   (hashx-create-handle! hashq-cons-hash hashq-cons-assoc table key init))
  77
  78 (define-public (hashq-cons-ref table key)
  79   (hashx-ref hashq-cons-hash hashq-cons-assoc table key #f))
  80
  81 (define-public (hashq-cons-set! table key val)
  82   (hashx-set! hashq-cons-hash hashq-cons-assoc table key val))
  83
  84 (define-public (hashq-cons table a d)
  85   (car (hashq-cons-create-handle! table (cons a d) #f)))
  86
  87 (define-public (hashq-conser hash-tab-or-size)
  88   (let ((table (if (vector? hash-tab-or-size)
  89                    hash-tab-or-size
  90                    (make-doubly-weak-hash-table hash-tab-or-size))))
  91     (lambda (a d) (hashq-cons table a d))))
  92
  93
  94 \f
  95
  96 (define-public (make-gc-buffer n)
  97   (let ((ring (make-list n #f)))
  98     (append! ring ring)
  99     (lambda (next)
 100       (set-car! ring next)
 101       (set! ring (cdr ring))
 102       next)))