From: noreply@...
Date: 2006-04-11T04:38:10+09:00
Subject: [ ruby-Bugs-4060 ] Array#- fails on arrays of user-defined classes

Bugs item #4060, was opened at 2006-04-10 14:38
You can respond by visiting: 
http://rubyforge.org/tracker/?func=detail&atid=1698&aid=4060&group_id=426

Category: Core
Group: None
Status: Open
Resolution: None
Priority: 3
Submitted By: Mat Schaffer (schapht)
Assigned to: Nobody (None)
Summary: Array#- fails on arrays of user-defined classes

Initial Comment:
Array#- does't appear to use ==, === or eql?.  I think it uses something below the ruby level.

When working with user-defined classes, Array#- considers identical objects to be equal.

I would understand if it used .equal?, but it doesn't because Array#- works on strings as if == was called.  Here's an example.

--------------------
class MyClass
  def ==(b)
    true
  end
end

p [MyClass.new, MyClass.new, MyClass.new] - [MyClass.new, MyClass.new]
--------------------

Expected: []
Observed: [#<MyClass:0x26080>, #<MyClass:0x2606c>, #<MyClass:0x26058>]

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You can respond by visiting: 
http://rubyforge.org/tracker/?func=detail&atid=1698&aid=4060&group_id=426