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Andrew Hume  
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 More options Jul 24 2007, 11:55 am
From: Andrew Hume <and...@research.att.com>
Date: Wed, 25 Jul 2007 00:55:25 +0900
Local: Tues, Jul 24 2007 11:55 am
Subject: object equivalence
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i have two objects, a and b, both of the same class.
i believe they have the same contents, but
        a.eql?(b) returns false

if i write a method xxx that returns as a string the value of every  
field
(much as to_s does), then a.xxx.hash == b.xxx.hash.
i believe this latter shows a and b are equivalent; o why
doesn't eql? agree?

------------------
Andrew Hume  (best -> Telework) +1 732-886-1886
and...@research.att.com  (Work) +1 973-360-8651
AT&T Labs - Research; member of USENIX and LOPSA


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Todd Benson  
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 More options Jul 24 2007, 2:27 pm
From: "Todd Benson" <caduce...@gmail.com>
Date: Wed, 25 Jul 2007 03:27:01 +0900
Local: Tues, Jul 24 2007 2:27 pm
Subject: Re: object equivalence
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On 7/24/07, Andrew Hume <and...@research.att.com> wrote:

> i have two objects, a and b, both of the same class.
> i believe they have the same contents, but
>         a.eql?(b) returns false

> if i write a method xxx that returns as a string the value of every
> field
> (much as to_s does), then a.xxx.hash == b.xxx.hash.
> i believe this latter shows a and b are equivalent; o why
> doesn't eql? agree?

eql? is just a method and therefore depends on the implementing
object.  By default, eql? returns true only if the objects being
compared are the _same_ object.  And then, each class typically
overrides eql? to do as the developer sees fit.

Todd


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