From: Rein Henrichs <reinh@...>
Date: 2010-06-11T00:30:05+09:00
Subject: Re: comparing objects

On 2010-06-10 06:59:40 -0700, Robert Dober said:

> On Thu, Jun 10, 2010 at 3:41 PM, Wilson Bilkovich <wilsonb@gmail.com> wrote:
> Even if
>> your code lives in isolation, ensuring proper semantics via these
>> methods prevents a class of tricky bug that your successors may have
>> to deal with.
> Hmm? Would you care to show an example where overloading those methods
> (#eql? and #hash) is needed to ensure proper behavior? I am willing to
> learn. But I am not willing to accept this statement as such.
> Cheers
> R.

You have been presented with one in this very thread. The OP wants 
objects of his class to have the correct semantics for Array#& and 
Hash#[], etc. The correct answer is to implement #hash and #eql?, just 
as implementing <=> provides objects of his class with the correct 
semantics for Array#sort.

-- 
Rein Henrichs
http://puppetlabs.com
http://reinh.com