From: "Ara.T.Howard" <ahoward@...>
Date: 2004-04-16T03:04:10+09:00
Subject: Re: Hash, ==,  key-value comparison

On Fri, 16 Apr 2004 walter@mwsewall.com wrote:

> Ok,
> 
> ALthough the docs don't mention it, Hash comparison using == checks 
> not only the key value pairs, but also the default value / default 
> procs.
> 
> So how does one compare 2 hashes key-value pairs.  I can see that it 
> might be useful to distinguish between 2 hashes whose key-value pairs 
> are the same but the default value/default proc are different, but I 
> would think that would be much less often than wanting to know if the 
> key-value pairs are the same.
> 
> Maybe I am thinking about this all wrong, but I always viewed a Hash 
> as a Hash, and yes some might have a default value and some might 
> have a default proc, but it is the data (the key-value pairs) that, 
> to me, make up the Hash.  The default data/procs are convenience that 
> make it easier to work with a Hash, but I would think that {} and 
> Hash.new(3) would be == if their key-value pairs would be equal.
> 
> Assuming that I am in the minority here about ==, what is the proper 
> way to see if 2 Hashes key-value pairs are the same.

how about

  (a.keys - b.keys).empty? and (a.values - b.values).empty?

-a
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