From: Dave Thomas <Dave@...>
Date: 2001-07-10T12:43:47+09:00
Subject: [ruby-talk:17592] Re: Constants and Variables

"HarryO" <harryo@zipworld.com.au> writes:

> However ...  I figured I could then do 
> 
> 	max_size = 10
> 	max_size.freeze
>         max_size = 5					# 3
>         puts "max = #{max}"		 # 4
> 
> and line 3 would produce an error, line 4 would print 10.

max_size is a variable that references an object. The variable is not
frozen.

Fixnums are a bad thing to use, because they have slightly different
semantics to other objects. Let's use Strings.


   a = "hello"


            ___             __String___
           | a | --------->| hello     |
            ---             -----------

   a.freeze

            ___             __String___
           | a | --------->| hello     | (frozen)
            ---             -----------

   a[3] = 'f'  ### error


   a = "goodbye"

            ___             __String___
           | a | --------->| goodbye   |
            ---             -----------

There's no error: you're not trying to change the frozen
object. You're just setting 'a' to reference a different object.


Dave