From: Austin Ziegler <halostatue@...>
Date: 2004-12-07T08:24:18+09:00
Subject: Re: Freezing Variable Assignment

On Tue, 7 Dec 2004 07:12:37 +0900, itsme213 <itsme213@hotmail.com> wrote:
> "Eric Hodel" <drbrain@segment7.net> wrote
>>> Correct. All instance variables of the object are frozen, not
>>> the objects they refer to.
>> No, the instance variables are not frozen, the instance 'a' of
>> Effable is.
>> 
>> #a= modifies a, which is disallowed because a is frozen.
>> 
>> You cannot freeze variables, just objects.
>> 
>> a = "foo"
>> a.freeze
>> a = "bar"
> I respecfully but heartily disagree. Ruby freezes objects by
> freezing their instance variables. The latter is the fundamental
> operation.

You may disagree, but you'd be incorrect.

irb(main):008:0> class << a
irb(main):009:1>   def matz
irb(main):010:2>     "matz"
irb(main):011:2>   end
irb(main):012:1> end
TypeError: can't modify frozen object
        from (irb):9

(Assuming the same Effable that has been discussed to this point.)

The object referred to by 'a' is frozen, not the instance variables
of said object.

The fundamental operation is *freezing the object*.

> @a = "foo"
> self.freeze
> @a = "bar"
> 
> Ruby just happens to treat local variables differently. There is
> no fundamental reason to do so.

Sure there is, and it's precisely because variables are simply
labels, but instance variables are part of the state of the object.

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