From: John Joyce <dangerwillrobinsondanger@...>
Date: 2007-05-09T09:34:04+09:00
Subject: Re: Equality question


On May 9, 2007, at 1:55 AM, Brian Candler wrote:

> On Wed, May 09, 2007 at 12:58:01AM +0900, Sebastian Hungerecker wrote:
>> Brian Candler wrote:
>>> o1 = [:defuzz_configs, {"conf"=>"foo.txt"}]
>>> o2 = [:defuzz_configs, {"conf"=>"foo.txt"}]
>>> p o1 == o2              # prints true
>>> p o1.hash == o2.hash    # prints false ??             <<<<<<<<<<<
>>
>> That's because the Hashs in o1 and o2 are two different objects.
>
> So hashes and arrays don't behave the same in this regard?
>
> o1 = ["hello", ["world"]]
> o2 = ["hello", ["world"]]
> p o1 == o2
> p o1.hash == o2.hash    # prints true
>
> o1 = {"key"=>"hello"}
> o2 = {"key"=>"hello"}
> p o1 == o2
> p o1.hash == o2.hash    # prints false
>
> I wonder why this is?
>
I'm a bit confused by this too. I've got seemingly conflicting stuff  
here:

irb(main):001:0> h1 = ['hi', ['dude']]
=> ["hi", ["dude"]]
irb(main):002:0> h2 = ['hi', ['dude']]
=> ["hi", ["dude"]]
irb(main):003:0> h1.class
=> Array
irb(main):004:0> h2.class
=> Array
irb(main):005:0> h1 == h2
=> true
irb(main):006:0> h1[1] == h2[1]
=> true
irb(main):007:0> h3 = h2
=> ["hi", ["dude"]]
irb(main):009:0>  h2 == h3
=> true
irb(main):010:0> hash1 = {'greet' => 'hi'}
=> {"greet"=>"hi"}
irb(main):011:0> hash1.class
=> Hash
irb(main):012:0> hash2 = hash1
=> {"greet"=>"hi"}
irb(main):013:0> hash1 == hash2
=> true
irb(main):014:0> hash1[1]
=> nil
irb(main):016:0> hash1.inspect
=> "{\"greet\"=>\"hi\"}"
irb(main):017:0> hash1.class
=> Hash
irb(main):019:0> 'greet'
=> "greet"
irb(main):020:0> hash1['greet']
=> "hi"
irb(main):025:0> hash1['greet'] == hash2['greet']
=> true
irb(main):026:0> p h1 == h2
true
=> nil
irb(main):027:0> p hash1 == hash2
true
=> nil
irb(main):028:0> p hash1
{"greet"=>"hi"}
=> nil
irb(main):029:0> p hash1.hash
1773356
=> nil
irb(main):030:0> p hash1.to_hash
{"greet"=>"hi"}
=> nil
irb(main):031:0> p hash2.hash
1773356
=> nil
irb(main):032:0> hash1 == hash2
=> true
irb(main):033:0> hash1.hash == hash2.hash
=> true
irb(main):034:0> o1 = {"key" => "hi"}
=> {"key"=>"hi"}
irb(main):035:0> o2 = {"key" => "hi"}
=> {"key"=>"hi"}
irb(main):037:0> p o1 == o2
true
=> nil
irb(main):038:0> o1.hash
=> 1844056
irb(main):039:0> o2.hash
=> 1830256
irb(main):040:0> o1 = {"name" => "bob"}
=> {"name"=>"bob"}
irb(main):041:0> o2 = {"name" => "bob"}
=> {"name"=>"bob"}
irb(main):042:0> o1 == o2
=> true
irb(main):043:0> o1.hash
=> 1769496
irb(main):044:0> o2.hash
=> 1757086
irb(main):045:0> h1.hash
=> -382289162
irb(main):046:0> h2.hash
=> -382289162
irb(main):047:0> hash1.hash
=> 1773356
irb(main):048:0> hash2.hash
=> 1773356
irb(main):049:0>