From: Paul Brannan <paul@...>
Date: 2002-02-25T23:29:14+09:00
Subject: Re: dispatching and class references

On Sat, Feb 23, 2002 at 03:41:03PM +0900, Michal Rokos wrote:
> 	Paul: Do you think that there is no need for method like
> 	"deep_freeze"? (I don't care about name - you know what it
> 	should do.)

I think there is some use for such a method, but I'm not sure how it
should work.  Consider:

  class Bar
    def initialize(s)
      @s = s
    end
    def foo
      @s[0] = ?b
    end
  end

  s = 'foo'
  b = Bar.new(s)
  b.freeze
  b.foo
  p s #=> "boo"

Should the call to foo raise an exception?  If so, then should:

  s = 'foo'
  b = Bar.new(s)
  b.freeze
  s[0] = ?b
  p s #=> "boo"

also raise an exception?  Similarly, what about:

  class Foo
    def initialize(b)
      @b = b
    end
    def foo
      eval("x = 42", @b)
    end
  end

  x = 0
  f = Foo.new(binding)
  f.freeze
  f.foo
  p x #=> 42

vs.:

  x = 0
  f = Foo.new(binding)
  f.freeze
  x = 42
  p x #=> 42

Paul