From: Akinori MUSHA <knu@...>
Date: 2002-09-04T13:01:38+09:00
Subject: Re: Set.rb patch

At Wed, 4 Sep 2002 12:44:40 +0900,
I wrote:
> This is not eql?() is expected to be.  The only requirement to eql?()
> is make (a == b => a.eql?(b)) always true; in other words, guarantee
> (!a.eql?(b) => a != b).  See how Hash compares keys: PTR_NOT_EQUAL()
> in st.c.

D'oh, I was confused.  I meant (a.hash == b.hash => a.eql?(b)) i.e.
(!a.eql?(b) => a.hash != b.hash).

And the following test is an irrelevant requirement anyway:

> > +    def test_eql?
> > +       a = EqlClass.new 
> > +       b = EqlClass.new until b.hash == a.hash
> > +       assert !(Set[a].eql?(Set[b]))
> > +    end

I think x.eql?(y) does not need to be false for any given x and y.  It
is certainly not preferable but the following definition of a class is
possible and legal:

	class Foo
	  def hash
	    1
	  end

	  def eql?()
	    true
	  end
	end

Am I missing something?

-- 
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