From: David Alan Black <dblack@...>
Date: 2004-04-18T03:09:09+09:00
Subject: Re: New Local Variable Scope rule

Hi --

ts <decoux@moulon.inra.fr> writes:

> >>>>> "D" == David Alan Black <dblack@wobblini.net> writes:
> 
> D> Going back to the original point (more or less): I'm just a little
> D> perplexed by the whole idea of closures (blocks, Procs, lambdas)
> D> having this compile-time effect on local variables in their context of
> D> creation.  
> 
>  Well, actually this is at compile time that ruby make the difference
>  between local, block-local variable and method call.
> 
>  If I've well understood, in 2.0 this is not changed : the only difference
>  is how ruby make the difference between local and block-local variable.

That's my understanding too (see above).  I'm just not entirely
comfortable with it.

>  Now the worst case is perhaps this
> 
> svg% cat b.rb
> #!/usr/bin/ruby
> thr = []
> 5.times do |i|
>    thr << Thread.new do
>       a = i
>       Thread.stop
>       puts a
>    end
> end
> 
> thr.each {|t| t.run }
> svg%
>  
> svg% b.rb
> 0
> 1
> 2
> 3
> 4
> svg% 
> 
>  I'm not sure but I think that for 2.0 all threads will give the same
>  result.

I assume so; it's like your other example, where 2.0 behaves the way
pre-2.0 does with "a = nil" before the block.  To avoid it I guess
you'd have to do:

  ...  Thread.new do |a|   # etc.

to create a new 'a' each time.  


David

-- 
David A. Black
dblack@wobblini.net