Example of JRuby Fixnum problem.

overridden_fixnum_less_than.rb

#! /usr/bin/env ruby

class Fixnum
  def < (other)
    puts "Determining membership of #{self.inspect} in #{other.inspect}..."

    return false unless other
    if other.is_a? Enumerable or other.is_a? Array
      other >= self
    else
      puts "The given other is not a list.  Invoking super..."
      super
    end
  end
end
class Array
  def >= (other)
    return false unless other
    include? other
  end
end
class Object
  def in?(other)
    return false unless other
    return other.include?(self) if other.is_a? Enumerable or other.is_a? Array
    false
  end
end

puts "2.in? [ 1, 3, 5, 2, 7 ] # => #{2.in? [ 1, 3, 5, 2, 7 ]}"
puts "2 < [ 1, 3, 5, 2, 7 ] # => #{2 < [ 1, 3, 5, 2, 7 ]}"
puts "2 < 3 # => #{2 < 3}"