Considering for the sake of argument the possibility that it is a
legitimate bug, and not a result of misusing the language features, it is a
family of bug that will be more common than most, because it reflects a
style of programming that is rare in real Clojure code.
But it isn't a bug.
Lazy-seqs don't promise to be "as lazy as possible", and when we step
through the logic of the original code in Michael Blume's post, we can see
why chunking breaks it. Taking for granted that something lazy is realized
with a specific granularity is an error in Clojure (see also lazy-seqs used
inside with-open blocks or db transactions - the opposite error is common,
not being strict enough).
defn primes [] (let [primes' (atom nil)]
(reset! primes' (cons 2 (filter #(prime? @primes' %) (drop
3 (range)))))))
The first time through the above code, primes' will be empty, so the first
chunk of results will all be calculated with an empty list of candidate
divisors.
On Thursday, February 12, 2015 at 5:26:52 PM UTC-8, Jorge Marques Pelizzoni
wrote:
>
>
> Beautiful, Armando! Thanks for your the insight. Anyway, I really don't
> buy the "that's the way it is" argument. Totally looks like a bug and I
> don't find it a coincidence it is working differently in the development
> branch. Thank you all for your time :)
>
> Em quinta-feira, 12 de fevereiro de 2015 22:30:02 UTC-2, Armando Blancas
> escreveu:
>>
>> Jorge, I tried this on 1.6 and seemed to work:
>>
>> (def primes
>> (cons 2 (for [n (iterate inc 3) :when (prime? primes n)] n)))
>>
>>
>>
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