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(define (make-eq-map)
(define counter-table (make-hash-table (make-eq-comparator)))
(define used-table (make-hash-table (make-eq-comparator)))
(define counter 0)
(lambda (msg obj)
(case msg
((contains?) (hash-table-contains? counter-table obj))
((cycle-counter) (let ((num (hash-table-ref counter-table obj)))
(hash-table-set! used-table obj #t)
(string->symbol
(string-append "#"
(number->string num)
"#"))))
((cycle-used?) (hash-table-contains? used-table obj))
((intern!) (hash-table-set! counter-table obj counter)
(set! counter (+ counter 1)))
(else (error "invalid message" msg)))))
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