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Diffstat (limited to 'module/ice-9/hcons.scm')
-rw-r--r-- | module/ice-9/hcons.scm | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/module/ice-9/hcons.scm b/module/ice-9/hcons.scm new file mode 100644 index 000000000..7275cf476 --- /dev/null +++ b/module/ice-9/hcons.scm @@ -0,0 +1,80 @@ +;;; installed-scm-file + +;;;; Copyright (C) 1995, 1996, 1998, 2001, 2003, 2006 Free Software Foundation, Inc. +;;;; +;;;; This library is free software; you can redistribute it and/or +;;;; modify it under the terms of the GNU Lesser General Public +;;;; License as published by the Free Software Foundation; either +;;;; version 3 of the License, or (at your option) any later version. +;;;; +;;;; This library is distributed in the hope that it will be useful, +;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +;;;; Lesser General Public License for more details. +;;;; +;;;; You should have received a copy of the GNU Lesser General Public +;;;; License along with this library; if not, write to the Free Software +;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA +;;;; + + +(define-module (ice-9 hcons) + :export (hashq-cons-hash hashq-cons-assoc hashq-cons-get-handle + hashq-cons-create-handle! hashq-cons-ref hashq-cons-set! hashq-cons + hashq-conser make-gc-buffer)) + + +;;; {Eq? hash-consing} +;;; +;;; A hash conser maintains a private universe of pairs s.t. if +;;; two cons calls pass eq? arguments, the pairs returned are eq?. +;;; +;;; A hash conser does not contribute life to the pairs it returns. +;;; + +(define (hashq-cons-hash pair n) + (modulo (logxor (hashq (car pair) 4194303) + (hashq (cdr pair) 4194303)) + n)) + +(define (hashq-cons-assoc key l) + (and (not (null? l)) + (or (and (pair? l) ; If not a pair, use its cdr? + (pair? (car l)) + (pair? (caar l)) + (eq? (car key) (caaar l)) + (eq? (cdr key) (cdaar l)) + (car l)) + (hashq-cons-assoc key (cdr l))))) + +(define (hashq-cons-get-handle table key) + (hashx-get-handle hashq-cons-hash hashq-cons-assoc table key)) + +(define (hashq-cons-create-handle! table key init) + (hashx-create-handle! hashq-cons-hash hashq-cons-assoc table key init)) + +(define (hashq-cons-ref table key) + (hashx-ref hashq-cons-hash hashq-cons-assoc table key #f)) + +(define (hashq-cons-set! table key val) + (hashx-set! hashq-cons-hash hashq-cons-assoc table key val)) + +(define (hashq-cons table a d) + (car (hashq-cons-create-handle! table (cons a d) #f))) + +(define (hashq-conser hash-tab-or-size) + (let ((table (if (vector? hash-tab-or-size) + hash-tab-or-size + (make-doubly-weak-hash-table hash-tab-or-size)))) + (lambda (a d) (hashq-cons table a d)))) + + + + +(define (make-gc-buffer n) + (let ((ring (make-list n #f))) + (append! ring ring) + (lambda (next) + (set-car! ring next) + (set! ring (cdr ring)) + next))) |