array_remove.rb

#!/usr/bin/env ruby

def assert_equal(reference, value)
  raise "Expected #{value.inspect} to equal #{reference.inspect}" unless reference == value
end

class Array
  def remove(other)
    copy = self.dup
    other.each do |e|
      if index = copy.index(e)
        copy.delete_at(index)
      end
    end
    copy
  end
end

assert_equal [], [1,2,2] - [1,2]
assert_equal [2], [1,2,2].remove([1,2])