On 2012-09-19 20:57:59 -0700, John Clements wrote:
> (define thunk (lambda () 14))
>
> (for/list ([i 10][e (in-producer thunk #f)]) e)
>
> … but I feel like there must be some way to simply write (stream-take
> thunk 10). Am I missing something obvious?
How about
(for/list ([i 10]) (thunk))
? Or do you really want it to be a stream?
You could write `stream-take` and use `in-producer`, but unfortunately
sequences are not necessarily streams, so it doesn't seem to be much
better:
(require unstable/match)
(define/match (stream-take strm n)
[((? stream-empty?) n) empty-stream]
[(_ 0) empty-stream]
[(strm n) (stream-cons (stream-first strm)
(stream-take (stream-rest strm)
(sub1 n)))])
(stream-take (sequence->stream (in-producer thunk #f)) 10)
BTW: should `racket/stream` have `stream-take` and other friends like
`stream-drop`? They're in SRFI-41.
Cheers,
Asumu
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