From: Charles Oliver Nutter <charles.nutter@...>
Date: 2007-11-29T06:22:32+09:00
Subject: Re: Ruby needs continuations...

MonkeeSage wrote:
> On Nov 28, 9:41 am, Charles Oliver Nutter <charles.nut...@sun.com>
> wrote:
>> MonkeeSage wrote:
>>> You actually need a generator, which can be implemented with
>>> continuations, but doesn't have to be (in 1.9 the generators are
>>> implemented with threads -- have a look at generator.rb in 1.8 and 1.9
>>> to see the differences). Using generators, you can implement izip (and
>>> all of itertools if you'd like, though most of it already has
>>> equivalent ruby solutions). Here is a pretty close translation of the
>>> python given in the itertools docs:
>> Ruby 1.9 also moves continuations out of core, but provides a form of
>> bounded continuations (coroutines) that's possible to implement in JRuby:
>>
>> require 'fiber'
>> f = Fiber.new { a = 1; while true; Fiber.yield a; a += 1; end }
>> 5.times { puts f.resume }
>>
>> $ jruby -J-Djruby.compat.version=ruby1_9 fiber_example.rb
>> 1
>> 2
>> 3
>> 4
>> 5
>>
>> Under JRuby, it's using a native thread per live Fiber, so it's heavier
>> than in Ruby 1.9 which uses green threads. However they'll actually run
>> in parallel on JRuby, so that's a benefit. JRuby also supports a thread
>> pool in 1.1 that helps blunt the cost of spinning up native threads.
>>
>> - Charlie
> 
> I just tried the above izip function in jruby, but it only gave me two
> iterations...

Could be a bug in generator; could you try it on a more recent release 
(like 1.0.2 or 1.1b1) and report it if it's actually a problem?

http://jira.codehaus.org/browse/JRUBY

- Charlie