title: Ruby array intersection returning a blank array
body: <p>I'm very new to Ruby so please go easy on me.  I have this small function that doesn't want to perform an intersection command.  If I go into irb and enter the arrays then set the intersection command like: third_array = array1 &amp; array2, third_array returns the common element.  But when I run this snippet through irb, it just returns [ ].  Any suggestions?</p>
  
  <pre><code>class String
  
    define_method(:antigrams) do |word2|
  
      array1 = []
      array2 = []
      array1.push(self.split(""))
      array2.push(word2.split(""))
      third_array = array1 &amp; array2
        third_array
    end
  
  end
  </code></pre>