From: Mark Hubbart <discord@...>
Date: 2004-06-16T03:45:50+09:00
Subject: Re: undefine


On Jun 15, 2004, at 10:19 AM, tony summerfelt wrote:

> On Tue, 15 Jun 2004 14:55:05 +0900, you wrote:
>
>>> I did not advocate removing, a.k.a. undefining,
>>> instance variable,
>
> it would be a local variable i'd be undefining, probably not an
> instance variable (although i'd like that option also)

I think the whole point here is that it isn't Ruby-ish to rely on a 
variable being defined or not. Ruby wassn't built to do things in that 
way; a couple examples in this thread show how variables are 
automagically defined when code is parsed. They aren't defined at 
runtime, they are defined at eval time. So basically, If you are 
translating code from Perl that undefines local variables, you will 
have to find a different way of doing it, due to the way Ruby was 
designed. I doubt that this is likely to change, because it's part of 
how Ruby was designed.

If you know Ruby well, there is almost certainly a way to do it that is 
just as reasonable and sensical as the Perl way, but it would be 
sensical for Ruby.

>>> for global variables, and removal method for local
>>> variables make no sense at all.
>
> only if the logic you use makes the code smaller or more efficient...
>
> larry wall added it to perl for a reason, and i'm guessing that he
> thought it would be handy :)

It is very handy for Perl, I know :) I used to use it. But there are 
other ways of doing the same sort of thing. To translate the given code 
into Ruby, I would (assuming that Delta_DHMS() won't return nil) write 
'next unless diff.nil?', then later, 'diff = nil'. If there's a chance 
that the method might return nil, you can always use the trick Sean 
posted elsewhere on this thread.