/usr/share/gauche-0.9/0.9.1/lib/util/isomorph.scm is in gauche 0.9.1-5.
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;;; isomorph.scm - check isomorphism
;;;
;;; Copyright (c) 2000-2010 Shiro Kawai <shiro@acm.org>
;;;
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;;; modification, are permitted provided that the following conditions
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;;;
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; 2. Redistributions in binary form must reproduce the above copyright
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;;; documentation and/or other materials provided with the distribution.
;;;
;;; 3. Neither the name of the authors nor the names of its contributors
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;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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;;; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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;;;
(define-module util.isomorph
(use srfi-1)
(export isomorphic? object-isomorphic?)
)
(select-module util.isomorph)
(define (isomorphic? a b . args)
(define ctx (if (pair? args)
(if (hash-table? (car args))
(car args)
(error "hash table required, but got" (car args)))
(make-hash-table)))
(define (iso? a b)
(cond ((or (boolean? a) (char? a) (number? a) (undefined? a)
(eof-object? a))
(eqv? a b))
((eq? a '()) (eq? b '()))
((hash-table-get ctx a #f) ;node has been appeared
=> (lambda (bb) (eq? bb b)))
(else
(hash-table-put! ctx a b)
(cond ((pair? a) (and (pair? b)
(iso? (car a) (car b))
(iso? (cdr a) (cdr b))))
((string? a) (and (string? b) (string=? a b)))
((symbol? a) (eq? a b))
((keyword? a) (eqv? a b))
((vector? a) (vector-iso? a b))
(else (object-isomorphic? a b ctx))
))))
(define (vector-iso? a b)
(and (vector? b)
(let loop ((la (vector->list a)) (lb (vector->list b)))
(cond ((null? la) (null? lb))
((null? lb) #f)
((iso? (car la) (car lb)) (loop (cdr la) (cdr lb)))
(else #f)))))
(define (hash-iso? a b)
(and (hash-table? b)
(let loop ((la (hash-table-map a cons))
(lb (hash-table-map b cons)))
(cond ((null? a) (null? b))
((null? b) #f)
((assq (caar la) lb)
=> (lambda (p)
(and (iso? (cdar la) (cdr p))
(loop (cdr la) (alist-delete (caar la) lb)))))
(else #f)))))
(iso? a b)
)
(define-method object-isomorphic? (a b context)
(equal? a b)) ;default
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