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Fixed `stream-add-between'.

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Don't put an extra seperator element at the end of the stream.  Brings
it in-line with the list version (`add-between') and sequence
version (`sequence-add-between').  Includes a test.
This commit is contained in:
MartyNeal 2012-04-19 00:11:22 +00:00 committed by Eli Barzilay
parent 36dd749268
commit 6e1ee717f7
2 changed files with 11 additions and 7 deletions
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13
collects/racket/stream.rkt
View File

@ -156,8 +156,11 @@
(define (stream-add-between s e) (define (stream-add-between s e)
(unless (stream? s) (unless (stream? s)
(raise-type-error 'stream-add-between "stream" s)) (raise-type-error 'stream-add-between "stream" s))
(let loop ([s s]) (if (stream-empty? s)
(cond empty-stream
[(stream-empty? s) empty-stream] (stream-cons
[else (stream-cons (stream-first s) (stream-first s)
(stream-cons e (loop (stream-rest s))))]))) (let loop ([s (stream-rest s)])
(cond [(stream-empty? s) empty-stream]
[else (stream-cons e (stream-cons (stream-first s)
(loop (stream-rest s))))])))))

3
collects/tests/racket/sequence.rktl
View File

@ -1,4 +1,3 @@
(load-relative "loadtest.rktl") (load-relative "loadtest.rktl")
(Section 'sequence) (Section 'sequence)
@ -108,6 +107,8 @@
(sequence-ref (sequence-add-between (in-naturals) #t) 2)) (sequence-ref (sequence-add-between (in-naturals) #t) 2))
(test #t 'sequence-add-between (test #t 'sequence-add-between
(sequence-ref (sequence-add-between (in-naturals) #t) 3)) (sequence-ref (sequence-add-between (in-naturals) #t) 3))
(test 3 'sequence-add-between
(sequence-length (sequence-add-between (in-range 2) #t)))
(arity-test sequence-count 2 2) (arity-test sequence-count 2 2)
(test 0 'sequence-count (sequence-count even? empty-sequence)) (test 0 'sequence-count (sequence-count even? empty-sequence))