From: Devin Mullins <twifkak@...>
Date: 2005-12-30T14:25:50+09:00
Subject: Re: What is the difference between :foo and "foo" ?

For the heck of it, I decided to come up with my own Symbol analogy. 
Caveat reader:

A symbol is a bubble. In Ruby-land, there is this ever-present *ether* 
wherein lies an abundance of bubbles.

<picture of a bunch of bubbles, each with a symbol literal inside -- 
feel free to Gimp it into existence -- here's a starter kit: 
http://www.scrapbookerie.com/images/autocollants/Sticko-Bubbles.jpg>

Every symbol you could ever want is out there, in the ether, bubbling 
along. For every name, there is a single bubble. For every bubble, there 
is a single name.

When you assign +x = :mr_t+, as with all variable assignments, you're 
pointing x to the :mr_t object. Here, you're pointing at that bubble 
that the Ruby interpreter recognizes as :mr_t. For plausability reasons, 
the Ruby interpreter blows the :mr_t bubble the first time you mention 
its name, but for your sake, you can assume that the :mr_t bubble has 
always existed and always will exist -- it's just there, floating in the 
ether, waiting to be pointed to.

So from that description right there, we already know one thing we can 
do with bubbles--er, Symbols--determine equality. Are these two 
variables pointing to the same bubble? Find me the Hash value whose 
associated key is this bubble I'm pointing to right now. For programming 
convenience, these bubbles have names associated with them, but as far 
as your code is concerned, they're just bubbles. This is the magic 
behind {:server => 'localhost', :port => 80}, etc.

The other (principal) thing you can do with a bubble--eh, Symbol--is 
find out its name at runtime (thanks to #to_s or #id2name). Thus, 
attr_accessor :mcklellan is born. I'm passing along a pointer to the 
:mcklellan bubble. attr_accessor follows the pointer, talks to that 
bubble, asks it what its name is, and uses that information to define 
some methods. Here, :mcklellan is just used as a fancy shorthand for 
'mcklellan'. (It happens to be one I like, but I digress...)

So, uh, yeah. That's it. The End.

Ha, yeah, so that description is probably more unsettling than settling, 
but maybe it'll plant a seed of wisdom, or whatnot. Plus, I can rest 
easy, now that I've solved everybody's problems.

Devin
Did I really just digress into "The End"?