From: Yuh-Ruey Chen <maian330@...>
Date: 2008-11-01T03:49:01+09:00
Subject: Re: How to access to local variables in enclosing scopes?

On Oct 31, 12:59 pm, Robert Dober <robert.do...@gmail.com> wrote:
> Ruby, in it's infinite wisdom; gives you a cake that you can have and eat.
>
> x =  42
> def a; x end # does not work!!
> Why?
> Because it is efficient, there is no closure and that means one
> context less to look up at runtime.

Not particularly convinced with that. If Python handles it with ease
and apparently no runtime performance penalty, I don't see why Ruby
can't do the same.

I'm more convinced with the fragility argument I gave in my previous
post, which is why I proposed the "nonlocal" thing.

> If however you want the closure (as I often do) you can still do it
>
> x = 42
>
> class << self; self end.module_eval do
>   define_method :a do x end
>   define_method :a= do |new_x| x = new_x end
> end
>
> puts a
> a = 43
> puts a
> #! The next one is important !
> puts x
>
> Note the class << self; self end.module_eval
> but I guess you know why I am doing this...
>
> .. class << self
>  end
>
> does not create a closure.

That's pretty clever, albeit somewhat unreadable.  I'd prefer to keep
Ruby as readable as possible :)