From: Logan Capaldo <logancapaldo@...>
Date: 2006-08-01T04:23:27+09:00
Subject: Re: I thought this was the one that worked?


On Jul 31, 2006, at 2:49 PM, Eric Armstrong wrote:

> #!/usr/bin/env ruby
>
> repeat = 1
>
> def run
>   number_of_times = repeat
>   number_of_times.downto(0) do
>     puts number_of_times
>     sleep 1
>   end
> end
>
> run
> ----------------------------
>
> Fails: undefined variable, "repeat"
>        in first line of run method
>
> I would have sworn that this was the
> one that worked. I know that for a class
> definition, the value of "repeat" isn't
> known in an instance. That makes sense
> to me (now).
>
> But here, I'm in a script. I am continually
> surprised by this behavior. In my mental
> model, the run method is a "subsidiary"
> context of the larger context, and as such
> it should just "naturally" be aware of values
> defined in the wider context.
>
> Obviously, my mental model is way, way off,
> which is why I keep getting surprised. Can
> anyone enlighten me?
>
> thanks
> eric
>
>
>

repeat is a local variable. class, def, and module introduce a new  
scope without closing over their enclosing scope. Blocks introduce a  
new scope that does enclose it's enclosing scope.

repeat = 1 # local variable repeat

def run # I just introduced a new scope. I can't see local variables  
outside my body


define_method("run") { # I just introduced a new scope, but I'm also  
a closure, I can see repeat.

Note that this issue has nothing to do with instances vs. classes, etc.