From: Charles Oliver Nutter <charles.nutter@...>
Date: 2007-08-28T02:25:07+09:00
Subject: Re: Fibers in Ruby 1.9?

SASADA Koichi wrote:
> I think Fiber class is not needed for most of people.  Because 1.9
> support Enumerator as outer iterater (I'm not sure about this
> nameing) such as Java's Iterator or Python's Generator or Ruby's
> 'generator' library and so on.
...
> Main purpose of Fiber is to realise outer iterator.  In fact,
> Enumerator#next using Fiber.  So I think ruby/test_enumerator.rb is
> more important test than implement Fiber's methods.

Yes, we don't have the enumerator work started yet in JRuby, but I don't 
expect it to be too difficult. Primarily I'm interested in implementing 
the coroutine features of Fiber, and that much is mostly complete now in 
my implementation.

> Easy instruction:
> =================
> 
> Fiber#resume
>   Resume Fiber's context.
> 
> Fiber.yield(...)
>   return values to resuming context.

yield and resume aren't hard to do, so I have those working in JRuby now.

> Fiber.current
>   return current fiber.

current only works from within an explicitly-constructed Fiber; i.e. you 
  can't get a fiber out of an arbitrary thread. It wouldn't be hard to 
fix, though.

> Fiber#alive?
>   return if this fiber is alive or not.

Works ok.

> Fiber#transfer
>   tranfer fiber context.  This method break resume/yield
> (parent/child) relation, so we shouldn't use it (this method is
> similar to callcc).

As we discussed on line, since this is a continuation-style feature, 
JRuby would not be able to support if. If you moved this to unsafe/fiber 
as you mentioned on line it would provide a good division. JRuby could 
support the "safe" fiber behavior.

Thanks for the help...I'll let you know if I have more questions.

- Charlie