From: "Ara.T.Howard" <ahoward@...>
Date: 2004-02-17T00:34:55+09:00
Subject: Re: accessing constants from class methods

On Mon, 16 Feb 2004, daz wrote:

> Date: Mon, 16 Feb 2004 06:55:25 -0000
> From: daz <dooby@d10.karoo.co.uk>
> Newsgroups: comp.lang.ruby
> Subject: Re: accessing constants from class methods
> 
> 
> > David A. Black wrote:
> >
> > >OK, it's probably something simple but I'm staring and staring at the
> > >original code, and its output (which is the same as daz's code), and I
> > >can't figure out why it wasn't OK.
> > >
> > >Explanations welcome :-)
> > >
> >
> 
> Your post didn't get through to the NG, David.
> Ara probably didn't see it and there appeared to be no replies
> when I posted.
> 
> http://groups.google.com/groups?hl=en&th=5677a0c1234ad853
 
yes exactly - sorry david.

> I'm wary about the defined? keyword -- I can't find a good
> definition of what service it provides.
> 
> for i in 0..1   # (avoiding new scope)
>   puts defined? a
>                 a = 1
>   puts defined? a
>   puts '-' * 10
> end
> 
> #-> nil
> #-> local-variable
> #-> ----------
> #-> nil
> #-> local-variable
> #-> ----------
> 
> ## Strangely, for constants it works differently.
> 
> for i in 0..1
>   puts defined? X
>                 X = 1
>   puts defined? X
>   puts '-' * 10
> end
> 
> #-> nil
> #-> constant
> #-> ----------
> #-> constant
> #-> constant
> #-> ----------
> 
> ## The next test made me wonder if I can believe anything, any more.
> 
> for i in 0..1
>   puts defined? Z
>     const_set   Z, 1
>   puts defined? Z
>   puts '-' * 10
> end
> 
> #-> nil
> #-> C:/TEMP/rb3273.TMP:17: uninitialized constant Z (NameError)
> #->   from C:/TEMP/rb3273.TMP:15:in `each'
> #->   from C:/TEMP/rb3273.TMP:15


THIS is the error i was getting but couldn't seem to reproduce it in response
to an offline question from david.  now i see that i could have done something
very subtle to (re)create the bug...

thanks for the warning - i will be catious when using 'defined?' in the
future.

-a
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