ice-9/hcons.scm

   1 ;;; installed-scm-file
   2
   3 ;;;;    Copyright (C) 1995, 1996 Free Software Foundation, Inc.
   4 ;;;;
   5 ;;;; This program is free software; you can redistribute it and/or modify
   6 ;;;; it under the terms of the GNU General Public License as published by
   7 ;;;; the Free Software Foundation; either version 2, or (at your option)
   8 ;;;; any later version.
   9 ;;;;
  10 ;;;; This program is distributed in the hope that it will be useful,
  11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;;;; GNU General Public License for more details.
  14 ;;;;
  15 ;;;; You should have received a copy of the GNU General Public License
  16 ;;;; along with this software; see the file COPYING.  If not, write to
  17 ;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18 ;;;; Boston, MA 02111-1307 USA
  19 ;;;;
  20
  21 \f
  22 (define-module  #/ice-9/hcons)
  23
  24 \f
  25 ;;; {Eq? hash-consing}
  26 ;;;
  27 ;;; A hash conser maintains a private universe of pairs s.t. if
  28 ;;; two cons calls pass eq? arguments, the pairs returned are eq?.
  29 ;;;
  30 ;;; A hash conser does not contribute life to the pairs it returns.
  31 ;;;
  32
  33 (define-public (hashq-cons-hash pair n)
  34   (modulo (logxor (hashq (car pair) 4194303)
  35                   (hashq (cdr pair) 4194303))
  36           n))
  37
  38 (define-public (hashq-cons-assoc key l)
  39   (and l (or (and (pair? l)
  40                   (pair? (car l))
  41                   (pair? (caar l))
  42                   (eq? (car key) (caaar l))
  43                   (eq? (cdr key) (cdaar l))
  44                   (car l))
  45              (hashq-cons-assoc key (cdr l)))))
  46
  47 (define-public (hashq-cons-get-handle table key)
  48   (hashx-get-handle hashq-cons-hash hashq-cons-assoc table key #f))
  49
  50 (define-public (hashq-cons-create-handle! table key init)
  51   (hashx-create-handle! hashq-cons-hash hashq-cons-assoc table key init))
  52
  53 (define-public (hashq-cons-ref table key)
  54   (hashx-ref hashq-cons-hash hashq-cons-assoc table key #f))
  55
  56 (define-public (hashq-cons-set! table key val)
  57   (hashx-set! hashq-cons-hash hashq-cons-assoc table key val))
  58
  59 (define-public (hashq-cons table a d)
  60   (car (hashq-cons-create-handle! table (cons a d) #f)))
  61
  62 (define-public (hashq-conser hash-tab-or-size)
  63   (let ((table (if (vector? hash-tab-or-size)
  64                    hash-tab-or-size
  65                    (make-doubly-weak-hash-table hash-tab-or-size))))
  66     (lambda (a d) (hashq-cons table a d))))
  67
  68
  69 \f
  70
  71 (define-public (make-gc-buffer n)
  72   (let ((ring (make-list n #f)))
  73     (append! ring ring)
  74     (lambda (next)
  75       (set-car! ring next)
  76       (set! ring (cdr ring))
  77       next)))