From: mike.leddy@...
Date: 2007-02-09T06:30:11+09:00
Subject: Ruby hash equlity

Based on the description of Hash#==

" Equality---Two hashes are equal if they each contain the same
number of keys and if each key-value pair is equal to (according to
+Object#==+) the corresponding elements in the other hash."

I am having problems understanding the following:

$ irb
irb(main):001:0> VERSION
=> "1.8.5"
irb(main):002:0> a={:c => nil, :d => nil}
=> {:c=>nil, :d=>nil}
irb(main):003:0> b={:d => nil, :c => nil}
=> {:c=>nil, :d=>nil}
irb(main):004:0> # As expected this is true
irb(main):005:0* a == b
=> true
irb(main):006:0> c={:a => nil, a => nil, :b => nil}
=> {:b=>nil, :a=>nil, {:c=>nil, :d=>nil}=>nil}
irb(main):007:0> d={:b => nil, b => nil, :a => nil}
=> {:b=>nil, {:c=>nil, :d=>nil}=>nil, :a=>nil}
irb(main):008:0> # Unexpectedly false
irb(main):009:0* c == d
=> false

Shouldn't they be equivalent ?

Thanks,

Mike