From: Brian Candler <B.Candler@...>
Date: 2007-05-16T02:39:41+09:00
Subject: Re: Why was the "Symbol is a String"-idea dropped?

On Wed, May 16, 2007 at 12:23:09AM +0900, Gary Wright wrote:
> 
> On May 15, 2007, at 10:53 AM, Brian Candler wrote:
> 
> >On Tue, May 15, 2007 at 10:54:05PM +0900, Robert Dober wrote:
> >>On 5/15/07, Brian Candler <B.Candler@pobox.com> wrote:
> >><snip>
> >>>But then what you want are not symbols, but true immutable  
> >>>strings. By that
> >>>I mean: some object where I can write 10MB of binary dump. If I  
> >>>want to add
> >>>one character to the end of it, then I create another object  
> >>>containing
> >>>10MB+1byte of binary dump, and the old 10MB object is garbage- 
> >>>collected.
> >>But of course we have immutable strings already :)))
> >>
> >>class IString < String
> >>  def initialize str
> >>    super(str)
> >>    freeze
> >>  end
> >>end
> >
> >Yes, but it's not a singleton.
> 
> 
> You've stated or implied a couple of times in this discussion that
> symbols are 'singletons', but I thought the conventional definition
> of 'singleton' was of a class with only a single instance, where the
> instance is called a singleton.  That doesn't describe Ruby's symbols.
> 
> I think what you are getting at is the idea that identity and
> equality are one and the same for symbols.

No, that's not exactly what I meant, but sorry for not being more precise.
What I meant was: there is only ever one symbol object in existence for a
particular sequence of characters. :foo.object_id in one part of the program
is always the same as :foo.object_id elsewhere.

If it were Symbol.new("foo") always returning the same object then I guess
it would probably be called the multiton pattern.

Regards,

Brian.