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20 lines
611 B
Racket
20 lines
611 B
Racket
7 years ago
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#lang br
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(define the-ks (make-hash))
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(define xs (make-hash))
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(define is '(a b (c . h) d e f g h i j))
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(for ([(v i) (in-indexed is)]
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#:unless (hash-has-key? xs i))
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(report* xs i)
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(hash-set! xs i
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(let/cc k
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(let ([v (cond
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[(pair? v) (hash-set! the-ks (cdr v) k) (car v)]
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[else v])])
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(define tk (hash-ref the-ks v #f))
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(cond
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[tk
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(hash-remove! the-ks v)
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(tk (format "~a xref" v))]
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[else (format "just ~a" v)])))))
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