Duplicate keys in a Hash

ruby-talk
1

In the code below it appears Ruby is permitting duplicate keys. What's
happening?
--Brian

h = {}
h[{}] = "test1" #key is an empty hash
h[{}] = "test2" #2nd key is an empty hash -- two duplicate keys?
h.size # 2

{} == {} # => true empty hashes are equal

2

{}.eql? {}
# => false

{}.hash == {}.hash
# => false

I don't think Hash uses == at all.

···

On Thu, 2006-03-23 at 05:56 +0900, Brian Buckley wrote:

In the code below it appears Ruby is permitting duplicate keys. What's
happening?
--Brian

h = {}
h[{}] = "test1" #key is an empty hash
h[{}] = "test2" #2nd key is an empty hash -- two duplicate keys?
h.size # 2

{} == {} # => true empty hashes are equal

--
Ross Bamford - rosco@roscopeco.REMOVE.co.uk

3

The two empty hashes are equal, but they're not the same empty hash, if that makes sense. Try this:

irb(main):013:0> {}.object_id == {}.object_id
=> false

I hope this answers your question!

Cheers,
Eric

···

On Mar 22, 2006, at 3:56 PM, Brian Buckley wrote:

In the code below it appears Ruby is permitting duplicate keys. What's
happening?
--Brian

h = {}
h[{}] = "test1" #key is an empty hash
h[{}] = "test2" #2nd key is an empty hash -- two duplicate keys?
h.size # 2

{} == {} # => true empty hashes are equal