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Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes)

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Am 16.06.2013 00:18, schrieb markspace:
> On 6/12/2013 5:37 AM, Sebastian wrote:
>> Am 11.06.2013 23:27, schrieb Sebastian:
>> [snip]
>>>
>>> I have thought again, and will put something together on a blog. May
>>> take a day or two, I'll be back to post a link. It will still be hard
>>> to follow, though. Meanwhile, a good place to get started with the topic
>>> would be Maurice Naftalin's Lambda FAQ at http://www.lambdafaq.org/
>>>
>>> -- Sebastian
>>
>> I have written two blog entries about higher-order functions with Java 8
>> lambda expressions. They can be found at
>>
>> http://sebastian-millies.blogspot.de/
>
> So I had a chance to look at this a bit. Lambda are kind of cool. You
> can generate lists of number easily:
>
> static void test1() {
> Stream.iterate( 0, x -> x + 1 )
> ;
> }
>
yes, I think its a good thing this is being added to Java. A real advance.

> This actually runs, even though the list is infinite. Many streams are
> lazy, and don't evaluate unless asked for more. I guess the stream above
> initializes its values, but then never generates any numbers since it's
> never asked for any.
yes, that's how it works. By the way, streams are not only lazy, but 
many tasks that work on streams can be parallelized by just calling the 
parallel() method on the stream. That's explicit but unobtrusive - all 
the concurrent stuff happens under the hood (based on the 
fork-join-framework of Java 7). I haven't yet looked at this in detail, 
though.

[snip]

> So to make this print primes, we have to filter a little differently. I
> really didn't understand the code in your first post, so I might be
> missing some points here. But I followed the example that you linked to
> earlier:
>
> Cf. this paper by Melissa E. O’Neil:
> http://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf
>
> And I gave that a go. The trick is to define your own predicate. No,
> it's not really a lambda at that point, but it does work, and with less
> code than either your first example or your blog. (Although barely less.)
[snip]
that's good to see. Thanks for sharing the code. It's nice having a real 
sieve of Eratosthenes now. (But I still like the simple formulation of 
the naive algorithm, just for its looks - although objectively it 
performs worse.)

I also like your step-by-step exposition.

Best Regards,
Sebastian

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Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-04 23:54 +0200
  Re: Java 8 Streams and Eratosthenes Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-06-04 19:35 -0300
    Re: Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-05 09:03 +0200
      Re: Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-05 09:44 +0200
        Re: Java 8 Streams and Eratosthenes Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-06-05 17:43 -0300
          Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-10 01:27 +0200
            Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-06-09 22:28 -0300
              Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-10 19:43 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) markspace <markspace@nospam.nospam> - 2013-06-10 13:18 -0700
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-11 23:27 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-12 10:32 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-12 14:37 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) markspace <markspace@nospam.nospam> - 2013-06-12 12:05 -0700
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-12 22:53 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) markspace <markspace@nospam.nospam> - 2013-06-15 15:18 -0700
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-16 22:52 +0200
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-06-16 21:56 -0300
                Re: Lazy primes with Java 8 (was Re: Java 8 Streams and Eratosthenes) Sebastian <news@seyweiler.dyndns.org> - 2013-06-18 23:18 +0200
  Re: Java 8 Streams and Eratosthenes markspace <markspace@nospam.nospam> - 2013-06-04 17:24 -0700
    Re: Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-05 09:09 +0200
      Re: Java 8 Streams and Eratosthenes markspace <markspace@nospam.nospam> - 2013-06-05 09:45 -0700
        Re: Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-05 21:32 +0200
    Re: Java 8 Streams and Eratosthenes Sebastian <news@seyweiler.dyndns.org> - 2013-06-05 09:47 +0200

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