From: Robert Dober <robert.dober@...>
Date: 2006-11-13T00:22:26+09:00
Subject: Re: Create local variable in Binding after it's creation

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On 11/12/06, Mauricio Fernandez <mfp@acm.org> wrote:
>
> On Sun, Nov 12, 2006 at 11:06:44PM +0900, Christian Surlykke wrote:
> > Is it possible to create a new local variable in a binding after it's
> creation?
>
> You can create it, but you won't be able to use it directly.
>
> > Specifically, what I'd like to do:
> >
> >   l = lambda { puts a }  # 'a' not defined at this point.
> >   eval('a = 7', l.binding)  # Hope to create a in l's binding
> >   l.call                             # Hope to get '7'
>
> l = lambda{ eval 'a' }
> eval('a = 7', l.binding)
> l.call                                             # => 7
> eval('a')                                          # => 7
>
> If you try to use 'a' before the parser sees 'a = ...', it will be
> considered
> a method call, and you'll get a NameError even if you give it a value
> afterwards/in eval.
>
> BTW. this is changing in 1.9.
>
> --
> Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby
>
> I do not want to argue with Mauricio, I know when I am outclassed(1), but
maybe one should suggest a different approach to OP.
Can you use instant variables, or will that be impacting elsewhere

p = Proc.new { puts @a }
@a= Guess what?
p.call

And yes Mauricio can you give a pointer to the new behavior please, thx.

Cheers
Robert



(1) Well I do not, but that remains between us ;)


-- 
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man.

- George Bernard Shaw

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