From: Ryan Leavengood <leavengood@...>
Date: 2005-10-20T23:01:52+09:00
Subject: Re: DbC, const and freeze.

On 10/19/05, John Carter <john.carter@tait.co.nz> wrote:
>
> For example, look at this hole...
> irb
> irb(main):001:0> a = [[1,2],[3,4]]
> => [[1, 2], [3, 4]]
> irb(main):002:0> a.freeze
> => [[1, 2], [3, 4]]
> irb(main):003:0> a << [9]
> RuntimeError: can't modify frozen array
>         from (irb):3:in `<<'
>         from (irb):3
>         from :0
> irb(main):004:0> a[0]<<1
> => [1, 2, 1]
> irb(main):005:0> a
> => [[1, 2, 1], [3, 4]]
> irb(main):006:0>
>
> Even though "a" was frozen, I still could modify the things "a" contained.

Fair enough. How about this:

irb(main):001:0> class Object
irb(main):002:1> def deep_freeze
irb(main):003:2> self.freeze
irb(main):004:2> if self.respond_to? :each
irb(main):005:3> self.each do |i|
irb(main):006:4* i.deep_freeze
irb(main):007:4> end
irb(main):008:3> end
irb(main):009:2> end
irb(main):010:1> end
=> nil
irb(main):011:0> a=[[[1,2,3],[4,5]],[6,7]]
=> [[[1, 2, 3], [4, 5]], [6, 7]]
irb(main):012:0> a.deep_freeze
=> [[[1, 2, 3], [4, 5]], [6, 7]]
irb(main):013:0> a << 9
TypeError: can't modify frozen array
        from (irb):13:in `<<'
        from (irb):13
irb(main):014:0> a[0] << 9
TypeError: can't modify frozen array
        from (irb):14:in `<<'
        from (irb):14
irb(main):015:0> a[0][0] << 9
TypeError: can't modify frozen array
        from (irb):15:in `<<'
        from (irb):15
irb(main):016:0>

Does anyone else love that name? ;)

Ryan