From: Igal Koshevoy <igal@...>
Date: 2008-07-02T01:48:16+09:00
Subject: Re: Dynamic Variables

Charles Oliver Nutter wrote:
> Igal Koshevoy wrote:
>> # Python
>> counter = 52
>> eval(compile('box%s = "cat and dogs"' % counter, '<string>', 'exec'))
>> print box52 # => "cat and dogs"
>>
>> # Perl
>> $counter = 52;
>> eval("\$box$counter = 'cat and dogs'");
>> print $box52, "\n"; # => "cat and dogs"
>
> In python, local variables are not (necessarily) determined at 
> parse/compile time. They're slots in a local scope that can grow later 
> on.
>
> In Ruby, this behavior only exists for eval scopes. Ruby 1.8 shares a 
> single eval scope under any given normal scope across all evals in 
> that normal scope. Ruby 1.9 instantiates a new eval scope for each eval.
>
> I don't know what Perl does.
Charles, thanks for the clarification about the scoping behaviors.


I suppose if I really want to pretend like I was dynamically injecting a 
local variable into a local scope, and a class/instance variable didn't 
weren't desirable, then I could resort to:

def set(name, value)
  self.class.send(:attr_accessor, name)
  self.send("#{name}=", value)
end

counter = 52
set "box#{counter}", "cat and dogs"
p box52 # => "cat and dogs"

-igal