ruby/cmp.rb


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#!/usr/bin/env ruby


class A
  attr_accessor :a

  def initialize a
    @a = a
  end

  def == other
    @a.size == other.a.size
  end
  alias :eql? :==

  def hash
    @a.hash
  end
end

a = A.new 'a'
b = A.new 'b'
ax = A.new 'a'

puts a == ax

l = [a, b, ax]
puts l.uniq.size