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sequence-length: special case O(1) cases.

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This commit is contained in:
Vincent St-Amour 2016-01-02 20:05:04 -06:00
parent 47f06f11e1
commit c47c0ebfca
1 changed files with 5 additions and 2 deletions
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5
racket/collects/racket/sequence.rkt
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@ -41,8 +41,11 @@
(define (sequence-length s)
(unless (sequence? s) (raise-argument-error 'sequence-length "sequence?" s))
(cond [(vector? s) (vector-length s)]
[(hash? s) (hash-count s)]
[else
(for/fold ([c 0]) ([i (in-values*-sequence s)])
(add1 c)))
(add1 c))]))
(define (sequence-ref s i)
(unless (sequence? s) (raise-argument-error 'sequence-ref "sequence?" s))