From: Robert Klemme <shortcutter@...>
Date: 2007-05-16T00:10:07+09:00
Subject: Re: Why was the "Symbol is a String"-idea dropped?

On 15.05.2007 16:34, Robert Dober wrote:
> On 5/15/07, Robert Klemme <shortcutter@googlemail.com> wrote:
>> On 15.05.2007 15:54, Robert Dober wrote:
>> > On 5/15/07, Brian Candler <B.Candler@pobox.com> wrote:
>> > <snip>
>> >> But then what you want are not symbols, but true immutable strings. By
>> >> that
>> >> I mean: some object where I can write 10MB of binary dump. If I want
>> >> to add
>> >> one character to the end of it, then I create another object 
>> containing
>> >> 10MB+1byte of binary dump, and the old 10MB object is 
>> garbage-collected.
>> > But of course we have immutable strings already :)))
>> >
>> > class IString < String
>> >   def initialize str
>> >     super(str)
>> >     freeze
>> >   end
>> > end
>>
>> What advantages does this have over using "freeze" directly?
> 
> Dunno :)
> 
> x = IString.new("Hello World") # Not even tested yet
> vs.
> x="HelloWorld".freeze
> 
> Well the first one has the advantage that I thought about it ;)
> 
> Now I reckon that the subclass stuff is baaad
> 
> def blah str
>    raise ArgumentError unless IString === str
>    ...
> end
> 
> but now someone does
> class MString < IString
>   get rid of the freeze (by calling superclass.superclass.new in
> self.class.new e.g)
> end
> 
> and my code is broken, while in
> 
> 
> def blah str
>    raise ArgumentError unless str.respond_to? :frozen && str.frozen?
>   ...
> end
> 
> frozen is frozen forever.

Corrent.  And since #frozen? is defined in Kernel you can skip the first 
test.

> So do what Robert told you and beware of what Robert told you;)

:-)

>> > You see things; and you say Why?
>> > But I dream things that never were; and I say Why not?
>> > -- George Bernard Shaw
>>
>> Greetings to George, btw. :-)
> Well last time I met him he was admiring your posts to the list :-P

Wow!  So he didn't die but just went home like this other guy who 
invented a vi clone (or at least provided his name for the operation)... :-)

>>         robert
>>
>>
> idem

:-)

While we're at it: *if* you want to define something (and are a fan of 
C++) you can do this:

irb(main):001:0> module Kernel
irb(main):002:1> private
irb(main):003:1> def const(*a) a.each {|x| x.freeze } end
irb(main):004:1> end
=> nil
irb(main):005:0> nil
=> nil
irb(main):006:0> foo, bar = const "foo", "bar"
=> ["foo", "bar"]
irb(main):007:0> ["foo", "bar"]
=> ["foo", "bar"]
irb(main):008:0> foo << bar
TypeError: can't modify frozen string
         from (irb):8:in `<<'
         from (irb):8
         from :0
irb(main):009:0> bar << foo
TypeError: can't modify frozen string
         from (irb):9:in `<<'
         from (irb):9
         from :0
irb(main):010:0>

Hihi...

Kind regards

	robert