From: Ken Bloom <kbloom@...>
Date: 2009-01-02T12:37:38+09:00
Subject: [ruby-core:21058] Re: Definable != is a Bad Thing???

Ryan Davis <ryand-ruby@zenspider.com> wrote:
> 
> On Dec 29, 2008, at 17:13 , Yukihiro Matsumoto wrote:
> 
>> |== and != should not be able to contradict each other.
>> |
>> |Is this a bug? I looked at the code and it looks intentional. Should
>> |it be allowed?
>>
>> It's intentional.  Ruby's flexibility sometimes allows you to do some
>> nasty things.  Ruby consider you smart enough to avoid such
>> contradiction.
> 
> ok... but why?

It's for doing things with builders, where you care about knowing
whether == or != was called, but you don't care so much about the
result (or the result is a dummy object that responds to more
messages and logs more stuff). For example in Ruby Quiz 95,
where the goal was to capture an s-expression representing an
expression, no pure-Ruby solution could capture ! or != in Ruby 1.8.
Now, in Ruby 1.9, they can capture ! and != without needing to resort
to RubyNode or ParseTree.

--Ken

-- 
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/