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reduce unnecessary vector-ref

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Sorawee Porncharoenwase 2021-01-03 20:47:27 -08:00 committed by Sam Tobin-Hochstadt
parent 6ace62a717
commit 64067704bc
1 changed files with 5 additions and 4 deletions
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9
racket/collects/racket/list.rkt
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@ -677,10 +677,11 @@
;; E.g., if N = 10 and we have #(3 4 8 9)
;; then we change it to #(3 5 6 7)
[index-to-change
(vector-set! k* index-to-change
(add1 (vector-ref k* index-to-change)))
(for ([i (in-range (add1 index-to-change) k)])
(vector-set! k* i (add1 (vector-ref k* (sub1 i)))))]
(define val-to-change (add1 (vector-ref k* index-to-change)))
(vector-set! k* index-to-change val-to-change)
(for ([i (in-range (add1 index-to-change) k)]
[v (in-naturals (add1 val-to-change))])
(vector-set! k* i v))]
;; Otherwise, there's no incrementable index. E.g.,
;; N = 10 and we have #(6 7 8 9), so we quit enumeration
[else (set! running? #f)])))]