From: Austin Ziegler <halostatue@...>
Date: 2005-01-14T23:29:20+09:00
Subject: Re: Mutable strings

On Fri, 14 Jan 2005 14:00:07 +0900, Mystifier
<mystifier@users.berlios.de> wrote:
> Dear Charles,
> 
> I have no intensions of changing the language APIs for it really
> does not matter to a VM Implementation. All the components that
> inherently affects the VM implementations are those that VM uses
> natively like File, Strings, Numbers and Threads.
> 
> I surprisingly found Symbols are exactly not Immutable...., they
> are just like any other class

Um. That's not the same at all. Symbols themselves are immutable.
The Symbol Class is not immutable.

Yes, this means that someone could override #to_s on Symbol to do
something else entirely, but Symbols themselves are immutable -- and
they cannot have virtual (singleton) classes:

  irb(main):001:0> foo = :foo
  => :foo
  irb(main):002:0> class << foo
  irb(main):003:1> end
  TypeError: no virtual class for Symbol
	  from (irb):2
  irb(main):004:0>

There is a significant difference between the two sorts of
immutability that you would be advised to understand before even
thinking of attempting to implement a VM to support Ruby.

-austin
-- 
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca