From: Mark Hubbart <discord@...>
Date: 2004-04-16T06:33:01+09:00
Subject: Re: Hash, ==,  key-value comparison


On Apr 15, 2004, at 10:04 AM, 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.

I posted this in another thread, but I figured I should dup it here:

for two hashes a and b:

   a.sort = b.sort

It converts them to arrays, and sorts them. This should do it.

> 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.

I agree that the way == works with hashes seems strange; I would expect 
it to just compare keys/values. OTOH, I can see how some might feel 
default values are an important part of determining equality.

cheers,
--Mark