gistfile1.txt

>gosh /home/shuji/gauche/debug/test.scm    
#?="/home/shuji/gauche/debug/test2.scm":23:(rp-dict)
#?-    #<hash-table eq? 0x99230f0>
#?="/home/shuji/gauche/debug/test2.scm":11:(rp-dict)
#?-    #<hash-table eq? 0x99230f0>
(1)#?="/home/shuji/gauche/debug/test2.scm":13:(rp-dict)
#?-    #f
*** ERROR: (rp-dict) is false
Stack Trace:
_______________________________________
  0  (scan-shared obj 0 0)
        At line 24 of "/home/shuji/gauche/debug/test2.scm"

test.scm

(use debug.test2)
(use gauche.generator)
(use gauche.lazy)

($ tt
$ generator->lseq
$ (cut gtake <> 10)
$ generate (^y (y 1)) )

test2.scm

(define-module debug.test2
  (use gauche.parameter)
  (export tt)
)
(select-module debug.test2)

(define rp-dict   (make-parameter #f)) ;table to count shared structure

(define simple-obj---? identity)
(define (simple-obj? x)
  #?=(rp-dict)
  (write x) (flush)
  #?=(rp-dict)
  (member x '("") ) )

(define (scan-shared obj level len)
  (rp-dict)
  (cond [(simple-obj? obj) #f]
        [else (unless (rp-dict) (error "(rp-dict) is false") ) ]))

(define (tt obj)
  (parameterize ( [rp-dict (make-hash-table 'eq?)] )
    #?=(rp-dict)
    (scan-shared obj 0 0) ) )