title: Julia: How to use/access the null value?
body: <p>In R the NA value is available by default however in Julia when I tried</p>
  
  <pre><code>function a()::Array{Union{Int64,Null})
    return [1, null, 2]
  end
  a()
  </code></pre>
  
  <p>it gives the error</p>
  
  <blockquote>
    <p>UndefVarError: Null not defined</p>
  </blockquote>
  
  <p>How do I use null in Julia?</p>