From: "David A. Black" <dblack@...>
Date: 2005-05-09T19:05:34+09:00
Subject: Re: No Thing Here vs Uninitialized and RCR 303

Hi --

On Mon, 9 May 2005, John Carter wrote:

> On Mon, 9 May 2005, David A. Black wrote:
>
>> Do you mean there's a convention of initializing variables to nil, prior to 
>> (say) their use as iterator variables or counters?  If so, that's very 
>> different from an uninitialized variable.
>
> Let me bounce that question back to you...
>
> When _you_ personally do that, what do you mean? Do you mean "This is ruby's, 
> umm, curious way of declaring local variables, namely by initializing them to 
> something. I am initializing this local variable to nil. By this I, David A. 
> Black mean (tick one)
>
>  a) This local variable is uninitialized and I wish ruby to throw an

Clearly I can't regard it as uninitialized, if I've just initialized
it.

>     error if I invoke a method on it before initializing it to
>     something meaningful.

You can't initialize a variable twice.  The second time around it's
just "assignment" :-)

[...]

> I can, and am currently writing a Nothing class that allows me to
> assign NOTHING, the sole instance of my Nothing class to a local
> variable in the case you describe.

I understand the goal of your project; I only mean to encourage you to
start from the clearest possible understanding of what the language
does -- specifically, that variables you have initialized to nil are
not uninitialized.  If you use the term "uninitialized" to describe
the x in "x = nil", I think snags in terminology and/or logic may
follow later on.


David

-- 
David A. Black
dblack@wobblini.net