Unit instances uniqueness (#hash)

[jackcasey]

Is this expected behaviour? FYI tested in ruby-units (1.4.3.7)

2.1.3 :001 > require "ruby_units"
true
2.1.3 :002 > ["2 kg".u, "2 kg".u].uniq
[
    [0] 2 kg,
    [1] 2 kg
]
2.1.3 :003 > "2 kg".u.hash
-2367612910358029872
2.1.3 :004 > "2 kg".u.hash
-1398046655738998000

To me this seems like a bug. Identical ruby unit instances (that are eql?) should hash to the same value right? (So .uniq? and any other operations that check the hash should work)

But I might be missing something subtle...